WHOLE TREE RENEWAL REGENERATES FRUITNG STRUCTURES QUICKLY IN MATURE ORCHARDS. James Edward Larson Jr. A THESIS

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1 WHOLE TREE RENEWAL REGENERATES FRUITNG STRUCTURES QUICKLY IN MATURE ORCHARDS By Jmes Edwrd Lrson Jr. A THESIS Sumitted to Michign Stte University in prtil fulfillment of the requirements for the degree of Horticulture Mster of Science 2017

2 ABSTRACT WHOLE TREE RENEWAL REGENERATES FRUITING STRUCTURES QUICKLY IN MATURE ORCHARDS By Jmes Edwrd Lrson Jr. Renewl of fruiting wood to mintin young reproductive meristems with optiml cnopy light interception nd distriution is key for high productivity nd fruit qulity throughout the life of sweet cherry (Prunus vium L.) orchrd. Typicl renewl involves replcement of 10 to 20% of the tree cnopy nnully y removing one to severl of the lrgest rnches. In mture orchrd, this renewl process is suject to competition etween sun-exposed fruiting sites nd interior cnopy renewl sites tht intercept less light nd compete poorly for trnslocted photossimiltes, often resulting in poor renewl growth. This is prticulrly prolemtic for high density orchrds tht utilize rootstocks selected for reduced vigor nd high productivity. Renewl of cnopy fruiting sites on whole tree sis is n lterntive renewl method tht elimintes the competitive inhiition of shoot regrowth. This study explores the initil response of sweet cherry trees on vrious trining systems nd size-controlling rootstocks to whole tree renewl. Four trining systems were studied: Tll Spindle Axe, Super Slender Axe, Upright Fruiting Offshoots, nd Kym Green Bush. In 2016, whole tree renewl of the four systems ws studied with Benton cultivr on three rootstocks of vrying vigor: Gisel 3, Gisel 5, nd Gisel 6. During loom, ll fruit-ering components of the cnopy were pruned ck to stus close to the permnent structure. TSA resulted in the higher numer of shoots, while KGB nd UFO hd the longest verge shoot length. The results indicte tht ech cnopy systemrootstock comintion refilled cnopy spce, except for KGB on ech rootstock, to quickly regenerte fruiting sites.

3 For my prents who hve lwys elieved in me. And to Becc for lwys mking me lugh iii

4 ACKNOWLEDGEMENTS I would first like to thnk my mjor dvisor, Dr. Greg Lng for providing me the opportunity to conduct this reserch; constntly providing help nd knowledge. Also, to my grdute committee: Dr. Frnk Telewski nd Polo Stini for eing ville for questions nd providing insight. I owe huge mount of grtitude to my l mtes: Tmmy Wilkinson, Feirn Li, Reecc Sely, nd Crly Diek; who ll helped me collect the dt within this thesis. They hve mde the work much more fun. iv

5 TABLE OF CONTENTS LIST OF TABLES.vii LIST OF FIGURES..viii THESIS INTRODUCTION. 1 Bckground..1 Thesis Contents 1 CHAPTER 1: A REVIEW OF THE LITERATURE Sweet Cherry Production in Michign.3 Growth nd Fruiting Hit...4 Role of Auxin nd Cytokinin in Brnching.5 Shoot Renewl nd Epicormic Brnching...7 Epicormic Vegettive Meristems.8 Sylleptic Brnching 11 Conclusions 12 LITERATURE CITED..17 CHAPTER 2: WHOLE TREE RENEWAL REGENERATES FRUITING STRUCTURES QUICKLY IN MATURE ORCHARDS 22 Introduction 22 Mterils nd Methods...24 Site nd Plnt Mteril...24 Whole Tree Renewl Pruning 25 Initil Regrowth Mesurements Mintennce Pruning...26 Cnopy Volume Mesurements.26 Covering System 27 Dt Anlysis nd Plot Design..28 Results 29 Cnopy Volume.29 Initil Growth Dt 29 Discussion..31 Conclusions APPENDIX...52 LITERATURE CITED.55 CHAPTER 3: MAPPING EPICORMIC VEGETATIVE MERISTEMS IN SWEET CHERRY USING X-RAY COMPUTER TOMOGRAPHY Introduction...59 Mterils nd Methods...61 Plnt Mteril.61 v

6 X-Ry Computer Tomogrphy Scn.61 3-Dimensionl Reconstruction...61 Results...62 Discussion Future Directions...64 LITERATURE CITED..70 vi

7 LIST OF TABLES Tle 2.1- Anlysis of vrince (ANOVA) for numer of renewl shoots following whole tree renewl pruning of eight-yer-old Benton sweet cherry trees, grown in the VOEN t MSU Clrksville Reserch Center. SSA dt left out.53 Tle 2.2- Anlysis of vrince (ANOVA) for numer of sylleptic rnches following whole tree renewl pruning of eight-yer-old Benton sweet cherry trees, grown in the CRAVO t MSU Clrksville Reserch Center. SSA dt eliminted to compre rootstocks..53 Tle 2.3- Anlysis of vrince (ANOVA) for numer of sylleptic rnches following whole tree renewl pruning of eight-yer-old Benton sweet cherry trees, grown in the VOEN t MSU Clrksville Reserch Center. SSA dt eliminted to compre rootstocks...54 vii

8 LIST OF FIGURES Figure 1.1- First yer of growth: rnch with single leves t ech node (Long et l., 2015)...14 Figure 1.2- Second yer of growth: sl fruit, vegettive spurs long one yer old growth, nd nnul extension of new growth (Long et l., 2015).14 Figure 1.3- Third yer of growth: fruiting spurs long two-yer-old growth, sl fruit on one yer old growth, followed y vegettive spurs, nd finlly nother section of new growth (Long et l., 2015) Figure 1.4- Scnning electronic microscope imge of smll preventitious epicormic uds without secondry ud primordi (Fontine et l., 1999) Figure 1.5- Lrge preventitious epicormic ud: SEM of lrge primry ud in the center, surrounded y secondry ud primordi (Fontine et l., 1999) Figure 2.1- Digrm of ech trining system used in the study. Kym Green Bush (KGB), Tll Spindle Axe (TSA), Super Slender Axe (SSA), nd Upright Fruiting Offshoots (UFO) Figure 2.2- SSA on Gi3 nd Gi6 whole tree renewl (WTR) cnopy verge spred versus spred of nnul prtil renewl (APR) trees t 0.75, 1.5, nd 2.25 meters in the cnopy. Cnopy spred verged over CRAVO nd VOEN t Michign Stte University s Clrksville Reserch Center, except where noted s CRAVO or VOEN. Lowercse letters seprte mens etween WTR nd APR t ech height tested using Tukey LSD were clculted t significnce of p Figure 2.3- TSA on Gi3, Gi5, nd Gi6 whole tree renewl (WTR) cnopy verge spred versus spred of nnul prtil renewl (APR) trees t 0.75, 1.5, nd 2.25 meters in the cnopy. Cnopy spred verged over CRAVO nd VOEN t Michign Stte University s Clrksville Reserch Center, except where noted s CRAVO or VOEN. Lowercse letters seprte mens etween WTR nd APR t ech height tested using Tukey LSD were clculted t significnce of p Figure 2.4- UFO on Gi3, Gi5, nd Gi6 whole tree renewl (WTR) cnopy verge spred versus spred of nnul prtil renewl (APR) trees t 0.75, 1.5, nd 2.25 meters in the cnopy. Cnopy spred verged over CRAVO nd VOEN t Michign Stte University s Clrksville Reserch Center, except where noted s CRAVO or VOEN. Lowercse letters seprte mens etween WTR nd APR t ech height tested using Tukey LSD were clculted t significnce of p Figure 2.5- KGB on Gi3, Gi5, nd Gi6 whole tree renewl (WTR) cnopy verge spred versus spred of nnul prtil renewl (APR) trees t 0.75, 1.5, nd 2.25 meters in the cnopy. Cnopy spred verged over CRAVO nd VOEN t Michign Stte University s Clrksville Reserch viii

9 Center, except where noted s CRAVO or VOEN. Lowercse letters seprte mens etween WTR nd APR t ech height tested using Tukey LSD were clculted t significnce of p Figure 2.6- Initil response numer of renewl rnches initited per permnent structure section, of TSA nd UFO grown on Gi3, Gi5, nd Gi6 fter whole tree renewl ws imposed. 5A- Brs re verge of 18 whole tree renewl trees grown in the CRAVO plus or minus stndrd error of the men. 5B- Brs re verge of 12 Whole tree renewl trees grown in the VOEN plus or minus stndrd of the men t Michign Stte University s Clrksville Reserch Center. Lowercse letters seprte mens compring cnopy sections, determined using Tukey s LSD, significnce t p Figure 2.7- Initil response numer of renewl rnch per permnent structure section of TSA, SSA nd UFO grown on Gi3 nd Gi6 fter whole tree renewl ws imposed. 5A- Brs re verge of 18 whole tree renewl trees grown in the CRAVO plus or minus stndrd error of the men. 5B- Brs re verge of 12 Whole tree renewl trees grown in the VOEN plus or minus stndrd of the men t Michign Stte University s Clrksville Reserch Center. Lowercse letters seprte mens compring cnopy sections, determined using Tukey s LSD, significnce t p Figure 2.8- Initil response numer of renewl rnch y rootstock verged over TSA, KGB nd UFO fter whole tree renewl ws imposed. Brs re n verge of 27 whole tree renewl trees grown in the CRAVO plus or minus stndrd error of the men t Michign Stte University s Clrksville Reserch Center. Lowercse letters seprte mens compring rootstocks, determined using Tukey s LSD, significnce t p Figure 2.9- Initil response numer of renewl rnch y trining system, verged over Gi3 nd Gi6. 8A- Brs re verge of 21 whole tree renewl trees grown in the CRAVO plus or minus stndrd error of the men. 5B- Brs re verge of 14 Whole tree renewl trees grown in the VOEN plus or minus stndrd of the men t Michign Stte University s Clrksville Reserch Center. Lowercse letters seprte mens compring trining systems, determined using Tukey s LSD, significnce t p Figure Averge length per renewl rnch, one seson of growth fter whole tree renewl ws imposed. Three-wy interction: permnent structure section y rootstock y trining system. TSA nd UFO oth grown on Gi3, Gi5, nd Gi6. 9A-Brs re n verge per section of 3 whole tree renewl trees grown in the CRAVO plus or minus stndrd error of the men. 9B- Brs re n verge per cnopy section of 4 whole tree renewl trees grown in the VOEN plus or minus stndrd error of the men t Michign Stte University s Clrksville Reserch Center. Lowercse letters seprte mens compring the system y rootstock y section interction, determined using Tukey s LSD, significnce t p Figure Averge length per renewl rnch, one seson of growth fter whole tree renewl ws imposed. Three-wy interction: permnent structure section y rootstock y trining system. TSA, SSA nd UFO oth grown on Gi3 nd Gi6.. Three-wy interction: permnent structure section y rootstock y trining system. Without Gi5 dt. 10A-Brs re n verge per ix

10 section of 3 whole tree renewl trees grown in the CRAVO plus or minus stndrd error of the men. 10B- Brs re n verge per cnopy section of 4 whole tree renewl trees grown in the VOEN plus or minus stndrd error of the men t Michign Stte University s Clrksville Reserch Center. Lowercse letters seprte mens compring the system y rootstock y section interction, determined using Tukey s LSD, significnce t p Figure Length per renewl rnch on whole tree sis verged over Gi3 nd Gi6. 11A- Brs re verge of 24 whole tree renewl trees grown in the CRAVO plus or minus stndrd error of the men. 11B- Brs re verge of 16 Whole tree renewl trees grown in the VOEN plus or minus stndrd of the men t Michign Stte University s Clrksville Reserch Center. Lowercse letters seprte mens compring the trining systems, determined using Tukey s LSD, significnce t p Figure Length per renewl rnch on whole tree sis verged over KGB, TSA, nd UFO. 12A-Brs re verge of 27 whole tree renewl trees grown in the CRAVO plus or minus stndrd error of the men. 12B- Brs re verge of 18 Whole tree renewl trees grown in the VOEN plus or minus stndrd of the men t Michign Stte University s Clrksville Reserch Center. Lowercse letters seprte mens compring rootstocks, determined using Tukey s LSD, significnce t p Figure Numer of sylleptic rnches on ech renewl prent rnch, per permnent structure section of TSA nd UFO on Gi3, Gi5, nd Gi6. Brs re verge of 18 whole tree renewl trees grown in the CRAVO plus or minus stndrd error of the men t Michign Stte University s Clrksville Reserch Center. Lowercse letters seprte mens compring the cnopy sections, determined using Tukey s LSD, significnce t p Figure Numer of sylleptic rnches on ech renewl prent rnch, per permnent structure section of TSA nd UFO on Gi3, Gi5, nd Gi6. Three wy interction: trining system y rootstock y permnent structure section. Brs re n verge per section of 12 whole tree renewl trees grown in the VOEN plus or minus stndrd error of the men t Michign Stte University s Clrksville Reserch Center. Lowercse letters seprte mens compring the system y rootstock y section interction, determined using Tukey s LSD, significnce t p Figure Numer of sylleptic rnches on ech renewl prent rnch, per permnent structure section of Gi3 nd Gi6 verged over TSA, SSA, nd UFO. Two-wy interction: rootstock y permnent structure section. Brs re n verge per section of 18 whole tree renewl trees grown in the CRAVO plus or minus stndrd error of the men t Michign Stte University s Clrksville Reserch Center. Lowercse letters seprte mens compring the rootstock y section interction, determined using Tukey s LSD, significnce t p Figure Numer of sylleptic rnches on ech renewl prent rnch, per permnent structure section of TSA, SSA, nd UFO verged over Gi3 nd Gi6. Two-wy interction: trining system y permnent structure section. Brs re n verge per section of 12 whole tree renewl trees grown in the VOEN plus or minus stndrd error of the men t Michign Stte x

11 University s Clrksville Reserch Center. Lowercse letters seprte mens compring the twowy interction, determined using Tukey s LSD, significnce t p Figure Numer of sylleptic rnches on whole tree sis y trining system. Averged over Gi3 nd Gi6. 17A- Brs re nd verge of 24 whole tree renewl trees grown in the CRAVO plus or minus stndrd error of the men. 17B- Brs re nd verge of 16 whole tree renewl trees grown in the VOEN plus or minus stndrd error of the men t Michign Stte University s Clrksville Reserch Center. Lowercse letters seprte mens compring trining systems, determined using Tukey s LSD, significnce t p Figure Trunk cross sectionl re in 2016 of ll loction y trining system y rootstock comintions in the NC-140 sweet cherry rootstock tril t Michign Stte University s Clrksville Reserch Center with Benton s the scion. Brs re n verge of 6 trees for ech KGB, TSA, nd UFO nd 12 trees for SSA on ech rootstock under the CRAVO; under the VOEN, 4 trees for KGB, TSA, nd UFO nd 8 trees for SSA on ech rootstock.49 Figure Density sctter plot of length per primry renewl rnch versus numer of sylleptic rnches per renewl rnch of trees tht hve een whole tree renewed. All dt is included, eing comprised of four different trining systems: KGB, TSA, SSA, nd UFO; three different rootstocks: Gi3, Gi5, nd Gi6 t Michign Stte University s Clrksville Reserch Center. Drker hexgon shde indictes higher numer of oservtions. A totl of 1362 primry rnches re plotted...50 Figure Violin plot of distriution of numer of sylleptic rnches per primry renewl rnch of trees tht hve een whole tree renewed. All dt is included, eing comprised of four different trining systems: KGB, TSA, SSA, nd UFO; three different rootstocks: Gi3, Gi5, nd Gi6 t Michign Stte University s Clrksville Reserch Center. Dt is roken up into percentile y renewl rnch length th nd th is the distriution of sylleptic rnches on 340 primry renewl rnches th nd th percentile is the distriution of sylleptic rnches on 341 primry renewl rnches th percentile represents the shortest 25% of rnches, rnch length increses with percentile.51 Figure 3.1- Scnning Electronic microscope imges of lrge preventitious epicormic ud (1A) with secondry ud primordi surrounding the ud in the center; smll preventitious epicormic uds (1B) without secondry ud primordi (Fontine et l., 1999).66 Figure 3.2- Imges in cross-section from X-ry CT scn of 8-yer-old section of sweet cherry of the vriety NY 119 grfted onto Gisel 12 rootstock trunk: 2A) complex epicormic trce, 2B) simple epicormic trce, 2C) V trce with centrl complex trce, flnked y simple trce on either side, 2D) sequentil rnch..67 Figure Epicormic rnches in cross-section: 3A) epicormic rnch 1 nd 2; 3B) epicormic rnch 3; 3C) epicormic rnch 4 nd 5; 3D) epicormic rnch 6 68 Figure 3.4- Epicormic rnch numer 6 with rection wood on the underside of the rnch..69 xi

12 THESIS INTRODUCTION Bckground Annul sweet cherry (Prunus vium L.) pruning includes the removl of one to severl of the lrgest rnches to mintin light distriution throughout the cnopy to decrese shding. Optiml light distriution is key for high productivity nd fruit qulity throughout the life of n orchrd. Pruning of the lrgest rnches usully initites new shoots tht emerge nd refill the cnopy, resulting in renewl of 10 to 20% of the cnopy ech yer nd fruit tht re consistently produced on reltively young rnches (Long et l., 2015). However, this renewl process cretes competition in the tree for photossimiltes etween fruiting meristems nd renewl of vegettive meristems (G.A. Lng, personl communiction). This competition is mgnified in high density orchrds tht utilize dwrfing rootstocks selected for high productivity ut reduced vigor; the result, typiclly, is poor or indequte regrowth to refill the cnopy (Lng, 2000; Perry et l., 1997). Renewl of the whole tree t once elimintes this competition, shifting the tree s physiology entirely to vegettive growth insted of lncing reproductive growth nd vegettive regenertion. Whole tree renewl removes the mjority of the previously ctive vegettive nd reproductive meristems on the tree, nd promotes the ctivtion of previously dormnt vegettive meristems to form new rnches nd the rpid refilling of the cnopy. Thesis Contents This thesis looks t two spects of whole tree renewl. First, n pplied study of trining systems nd rootstock vigor nd how these fctors ffected cnopy refill fter whole tree renewl ws imposed. Four trining systems: Tll Spindle Axe (TSA), Super Slender Axe (SSA), Kym Green Bush (KGB), nd Upright Fruiting Offshoots (UFO) were studied; ech on three 1

13 rootstocks: semi-vigorous Gisel 6 (Gi6), semi-dwrfing Gisel 5 (Gi5), nd dwrfing Gisel 3 (Gi3). The dt presented shows the initil regrowth tht occurred in the first yer fter whole tree renewl ws imposed t loom of 2016 nd the cnopy volume of the trees fter second seson of growth, The second component of this thesis tkes sic pproch to see how whole tree renewl cn e improved y mpping ltent uds using X-ry Computer Tomogrphy. This is preliminry study to determine first if it is possile to identify ltent uds from CT scn nd then look t how to mp ltent uds for the potentil to pinpoint where new rnch will rise fter pruning. 2

14 CHAPTER 1: A REVIEW OF THE LITERATURE Sweet Cherry Production in Michign Trverse City, Michign, is the self-proclimed cherry cpitl of the world, with Michign producing 75% of the domestic trt cherry (Prunus cersus L.) supply nd 20% of the sweet cherries (Prunus vium L.) grown ntionlly (Michign Ag Council, 2016). Lke Michign modertes the climte long the shoreline y rising the verge temperture in the winter while lso delying loom in spring, reducing the risk of frost dmge; therefore, vst mjority of the tree fruit crege in Michign is within 50 miles of Lke Michign (Schetzl, n.d.). Dwrfing rootstocks ecme ville lter to sweet cherries thn for pples (Mlus domestic Borkh.), therefore, mny sweet cherry orchrds re still grown t trditionl low plnting densities, trees per h -1, on vigorous rootstocks, e.g., Mzzrd (Prunus vium L.) nd Mhle (Prunus mhle L.). These trditionl orchrds produce lrge, complex tree cnopies tht re inefficient to mintin nd hrvest. First fruiting typiclly occurs in the fourth or fifth yer fter plnting nd the trees don t come into full production until 8-12 yers. However, the recent profits tht hve een relized in high density pple production hve sprked trnsition to pply those prctices to sweet cherries (Roinson et l., 2004). Dwrfing rootstocks imprt precocity nd high productivity (Lng, 2000; Perry et l., 1997), llowing cherry growers to plnt high density ( trees per h -1 ) orchrds tht relize full production quickly (5-7 yers). With high density systems, growers otin fster return on investment, pruning nd hrvest is more lor efficient, nd the opportunity to incorporte mechniztion with orchrd pltforms nd/or hedging is incresed. 3

15 Trnsitioning to high density systems hs rised questions on cnopy rchitecture, which trining systems to use, how to lnce crop lod, nd how to modify pruning. High density cnopy rchitectures emphsize simplicity, with n effort to crete fruiting wll tht mximizes light interception (Long et l., 2015). Sweet cherry trining systems tke mny different forms, with some hving centrl leder (e.g., Tll Spindle Axe, TSA; Super Slender Axe, SSA) nd others hving multiple leders (Kym Green Bush, KGB; Steep Leder, SL; Spnish Bush, SB). Some re 3-dimensionl cnopies (TSA, KGB, SL, SB), while some re nrrow plnr cnopies (SSA; Upright Fruiting Offshoots, UFO). Some re free stnding trees (TSA, KGB) nd others utilize trellis (SSA; UFO; Y-UFO). Growth nd Fruiting Hit As forest tree, sweet cherry s nturl growth hit is to produce vigorous, upright rnches to compete for light interception. The tree is therefore estlishing it s footprint, it s vegettive cnopy tht is lrge enough to compete for light with neighoring trees, efore trnsitioning to fruit production (Long et l., 2015). This is counterproductive to commercil production, since growers wnt to get orchrds into production s quickly s possile, nd develop compct trees with wek-to-modertely vigorous rnches. Queue dwrfing, precocious rootstocks nd simplified trining systems. The sweet cherry fruiting hit is such tht single rnch tkes three yers to otin ll of its fruiting components: single node leves, vegettive spur leves, reproductive spur leves, sl flowers, nd spur flowers. The first yer of growth is chrcterized y lrge single leves t ech node long the rnch (fig. 1.1). These simple uds t ech node cn develop further in one of few different wys in the following yers. The xillry meristems in the ud my remin primordil in the yer the ud develops; the ud will therefore remin in prdormncy (Lng, 4

16 1987) nd ecome engulfed y rdil growth of the rnch, persisting s ltent (preventitious epicormic) uds eneth the rk. Buds t the se of the shoot cn ecome fully reproductive meristems, i.e., single flower uds with no ccompnying vegettive meristem; fter fruiting occurs, these nodes ecome lind. The rest of the uds will either develop into new lterl rnch or spur, modified rnch with extremely short internodes nd rosette of five to eight leves (Ayl nd Lng, 2017). One-yer-old rnches usully hve few sl flower uds nd vegettive spurs. Flower uds egin forming in the lef xils of vegettive spurs, giving the potentil for fruiting spurs in yer 3. A new section of nnul growth develops from the terminl ud (fig. 1.2). By yer three, the rnch hs ll of its fruiting components: lind wood t the se, followed y fruiting (nd perhps some continuing non-fruiting) spurs, one-yer-old growth with sl flower uds nd vegettive spurs, nd finlly, nother section of nnul growth (fig. 1.3) (Ayl nd Lng, 2017). Mguylo et l. (2002) showed tht spur flower density increses from the sl to the distl end of ech mture nnul growth segment of rnch. Role of Auxin nd Cytokinin in Brnching The xillry meristem, giving rise to xillry uds nd eventully lterl rnches, is thought to e initited through two contrsting hypotheses: detched meristem nd de novo initition. The detched meristem hypothesis sttes tht the picl meristem cells tht never lost their meristemtic ctivity is the origin of the xillry meristem; the lterntive hypothesis sttes tht the xillry meristem forms de novo from the lef xil (Leyser, 2003). Auxin (indole-3-cetic cid) represses ud rek nd rnch development; this effect is elieved to occur fter xillry meristem initition (Leyser, 2003). Auxin is produced in the shoot pex nd newly formed leves (Ljung et l., 2001) nd moves down the stem through polr 5

17 trnsport (Wignll et l., 1987; Sunderg nd Uggl, 1998). Auxin production increses in uds s they ctivte (Hillmn et l., 1977), nd pplying uxin directly to ud does not inhiit rnch formtion fter removl of picl meristem (Cline, 1996). These two findings led to the conclusion tht uxin cts indirectly to inhiit rnching, minly y down-regultion of cytokinin synthesis nd export from roots (Leyser, 2003). Cytokinins (isopentenyldenine, zetin, nd dihydrozetin) ct directly on uds to promote rnching; pplictions of cytokinins to ud increse shoot outgrowth (Schs nd Thimnn, 1967). The RMS nd MAX fmily of genes, discovered in Pe (Pisum stivum) nd in Aridopsis thlin, respectively (Sorefn et l., 2003), re required for picl dominnce, leding to the elief tht moile signl serves s nother indirect mode of ction through which uxin inhiits rnching (Leyser, 2003). Rms nd mx mutnts re ushier nd show reduced response to uxin pplictions fter removl of the shoot pex (Sorefn et l., 2003). Grfting nd reciprocl grfting experiments with rms nd mx mutnts nd wildtypes hve shown tht this long-rnge signl is synthesized throughout the plnt: picl dominnce ws restored with: wildtype roots grfted on mutnt shoots, mutnt roots grfted onto wildtype shoots, nd even wildtype interstock etween mutnt shoot tissue. Wildtype tissue nywhere in the plnt is le to produce the long-rnge signl nd mintin picl dominnce (Leyser, 2003). The product of the rection tht the MAX/RMS-dependent signl ctlyzes to inhiit rnch development is unknown. However, uxin is known to up-regulte trnscription of RMS1 in pe; incresed production of RMS1 nd its product could e the indirect mechnism through which uxin inhiits rnching. The MAX pthwy seems to work different in Aridopsis, since uxininduced MAX4 expression in the root tip ws seen 24 h fter uxin tretment. This points to rnch inhiition eing post-trnscriptionl in Aridopsis (Leyser, 2003). 6

18 Shoot Renewl nd Epicormic Brnching The highest qulity cherries re orne on sl flower uds nd young spurs. Renewl of fruiting sites is therefore required to continully produce high qulity fruit throughout the life of n orchrd. Renewl is ccomplished y nnul removl of few of the lrgest rnches in the cnopy. Idelly, pruning of these rnches ck to short stus removes picl dominnce nd epicormic uds re relesed from prdormncy, developing into n epicormic rnch tht susequently refills the cnopy spce. Therefore, portion of the cnopy (~10-20%) is constntly eing renewed while fruiting occurs throughout the rest of the cnopy. Epicormic rnching is regenertive mesure of trees to increse lef re following dmge or stresses. Fire (Burrows, 2008), insect defolition (Piene nd Eveleigh, 1996), wind dmge (Cooper-Ellis et l., 1999), competition (Nicolini et l., 2001), nd vsculr emolism (Nicolini et l., 2001) hve ll een shown to initite epicormic rnching in trees. These stresses cese or limit uxin production from the picl meristem, removing the correltive inhiition of cytokinin iosynthesis nd the uxin-induced signling pthwy, s descried ove. In complex tree cnopy, removl of single rnch, s with typicl nnul renewl pruning in sweet cherry, only removes portion of the uxin tht is eing produced. Therefore, epicormic uds still hve the potentil to remin dormnt. Comining this sitution with the decresed vigor of trees on dwrfing rootstocks, which limits photossimilte supply for fruiting sites nd vegettive growth, cn result in inconsistent nnul renewl with typiclly either no new shoot growth or insufficient growth to refill the spce in high density sweet cherry orchrds. Pruning severity increses not only the numer of epicormic rnches tht sprout, ut lso the length of those epicormic rnches (O Hr nd Berrill, 2009). In costl redwood (Sequoi sempervirens [D. Don.] Endl.), O Hr nd Berrill showed no chnge in epicormic 7

19 rnching from crown removl tretments rnging from n untreted control up to 60% removl, ut with 85% removl, epicormics rnch numer, length, nd dimeter of rnch incresed. Gordon et l. (2006) lso showed light nd time of topping s significnt fctors ffecting initition of epicormic rnches in pech (Prunus persic Btsch.). Two flushes of epicormic rnches were seen; one eginning in Mrch nd dwindling in My, followed y n increse in June, with the highest sprouting occurring in August. Epicormic rnches during this second flush hd higher dry weight thn erly sprouting rnches. Light exposure ws positively correlted with epicormic sprouting; trees receiving no light hd 25% reduction in epicormic rnches initited (Gordon et l., 2006). It ws concluded tht pruning ffects epicormic rnching y removing picl dominnce nd incresing light exposure to epicormic uds. Epicormic Vegettive Meristems Epicormic uds re clssified s dventitious or preventitious (Fontine et l., 1998). Development is the key differentiting fctor, with preventitious epicormics uds developing from the picl meristem nd dventitious developing from previously non-meristemtic tissue (Brown, 1971; Fink, 1999). Preventitious epicormics uds were once xillry uds tht did not develop into rnch, remined dormnt nd were susequently engulfed y the rdil growth of the rnch, persisting eneth the rk (Büsgen nd Münch, 1929; Stone nd Stone, 1943). Preventitious epicormics ud formtion follows the phyllotxy of the tree; sweet cherry hs spirl phyllotxy with 5 nodes per doule revolution, ~every 144 (Lng et l., 2004; G.A. Lng, personl communiction). Adventitious epicormics develop exclusive of the norml phyllotxy, typiclly following wounding event (Fink, 1983, 1999; Kuppi et l., 1987). Formtion occurs in mture tissue or cllus (Stone nd Stone, 1943), in smll groupings of prenchym cells tht regin meristemtic 8

20 ctivity y sudivisions. Differentition of n pex nd prophylls follows. Lef primordi then rise from djoining prenchym cells. This completes the formtion of the ud nd vsculr tissue forms, inititing n epicormic trce (Fink, 1983). Adventitious epicormics uds re thought to contriute little to the overll epicormic potentil in unwounded trees. Preventitious epicormics uds mintin vsculr connection to the pith y 2-5 mm thick dense concentrtion of prenchym cells; this is known s n epicormic trce or ud trce (Fontine et l., 1998). This trce usully occurs perpendiculr to the pith of the min stem (Büsgen nd Münch, 1929; Colin et l., 2010) nd lengthens ech yer with nnul growth rings, with the vegettive meristem persisting just eneth the rk. Preventitious epicormics uds re seprted further into smll nd lrge uds. Smll preventitious epicormic uds mesure less thn 2 mm long (fig. 1.4) nd re typiclly ssocited with rings of ud scle scrs. Lrge preventitious epicormics uds mesure 3-4 mm long (fig. 1.5) nd re locted long the nnul shoot (Fontine et l., 1998). The upper third of lrge preventitious epicormics is chrcterized y meristemtic res mesuring 100 µm long nd 30 µm wide. Secondry ud primordi re present in the lower two thirds, within their primry ud. Smll preventitious epicormics do not hve these secondry uds, nd re composed only of terminl meristem surrounded y scles (Fontine et l., 1998). Lrge preventitious epicormic uds re more likely to sprout thn re smll preventitious epicormics uds (Brhm nd Kellison, 1987). Younger epicormic uds re lso more likely to sprout into n epicormic rnch thn re uds on older wood (Kormnick nd Brown, 1969; Colin et l., 2010). However, smller uds tend to persist for mny yers compred to lrge uds (Gruer, 1994) ecuse lrge epicormic uds tht do not form rnch re more likely to scise thn re smll uds (Hrmer, 1991; Fontine et l., 2001). 9

21 Epicormic trces differ in composition etween lrge nd smll dimeter stems in Euclyptus cldoclyx (Burrows, 2000). Strnds of smll stems ( cm dimeter) consisted of meristemtic tissue in 3-13 strips just ehind the ud; these strips were emedded in strnd of prenchym cells mm wide nd 2.0 mm high. The cells in the strnd ecme more lignified ner the pith. Strnds were more complicted in lrge dimeter (7-30 cm) stems. These strnds were most complex in the vsculr cmium, with n ellipticl shpe in trnsverse section contining16-40 meristemtic domes. Cmi t the edges of domes differentited into prenchym. Cmi produced ll the fetures of secondry xylem: fiers, fier trcheids, xylem prenchym nd ry prenchym. Strnds in stems greter thn 20 cm were significntly thicker thn thin stems, mesuring 3-5 mm high; some stems ctully consisted of two smller strnds. Strnd cross-sectionl re incresed with incresing stem dimeter (Burrows, 2000). Burrows (1989) exmined the development of xillry meristems following removl of the picl meristem on newly formed shoots in hoop pine (Arucri cuninghmii Aiton ex D. Don). At decpittion, picl meristem, lef primordi or vsculr connections were not present in the xillry meristem. A shell zone of thick-wlled cells in crescent shpe ws on the dxil side of the xillry meristem; periderm, the rk ptch, ws on the xil side. There ws n increse in nucleus size nd cytoplsmic density of the picl meristem on dy 3. Anticlinl cell division egn t the ck of the xillry meristem on dy 6 nd continued through dy 9. Domed ud primordi formed etween dys 9 nd 12 from periclinl divisions tht egn in the corpus of the xillry meristem. Lef primordi initition quickly followed on the picl dome. Two procmil strnds formed cross the cortex from corticl dedifferentition from nticlinl divisions. These two strnds followed prllel to ech other through most of the cortex, with the upper strnd moving perpendiculr to or slightly downwrd from the stem xis; the upper strnd 10

22 took strong downturn t the centrl vsculr cylinder. The lower strnd turned shrply efore the upper, t the inner cortex, joining the xil vsculr system. By dy 15, 3-5 lef primordi hd een initited, nticlinl division continued, enlrging procmil strnds (Burrows, 1989). Swelling of the xil occurred eginning t dy 6, nd y dy 18, it hd swelled lrge enough tht the rk ptch hd split nd the older lef primordi were visile in the lef xil. No new structures developed fter 21 dys, nd further growth ws continution of ongoing processes. A stem hd egun to form t dy 35, nd this stem hd developing uds. Burrows lso exmined ud development in old rnches nd found more sclerenchym rings in mture versus newly formed shoots, mening greter rrier to form vsculr connections for initited uds in mture shoots. Sylleptic Brnching Proleptic rnches develop from xillry uds in the yer fter the ud forms. However, sylleptic rnches grow in the sme yer tht their prent rnch originted (Spth, 1912). Proleptic rnches with sylleptic rnching hve higher trnsloction efficiency nd growth rte thn proleptic rnches without sylleptic rnching (Scrsci-Mugnozz et l., 1999). Compring three poplr (Populus tichocrp) hyrids, Cline nd Don-Il (2002) showed tht sylleptic rnching ws highest in the lest vigorous hyrid. The investigtors did note tht ll three clones hd reltively high growth rtes. Decpittion of the picl meristem followed y pplictions of synthetic uxin (1% nphthlenecetic cid) to mintin picl dominnce ws most effective in the fstest growing clone, resulting in decresed sylleptic rnching of the shoot rising from the top ud. It ws therefore concluded tht greter insensitivity to uxin is the cuse for incresed sylleptic rnching. Cytokinin pplictions of 1 mm enzyldenine to n inhiited ud were lest effective in the clone tht produced the fewest sylleptic rnches; 11

23 pplictions hd the gretest response in the clone tht formed n intermedite level of sylleptic rnches. These results prtilly supported the investigtors hypothesis tht higher sensitivity to cytokinin is responsile for incresed sylleptic production (Cline nd Dong-Il, 2002). Other studies hve exmined the growth hit of two pech vrieties, Pillr nd Stndrd. Stndrd trees hd more spreding orienttion nd lower uxin:cytokinin rtio hd incresed sylleptic rnching over the upright growth of Pillr (Tworkoski et l., 2006). Tworkoski et l. hypothesized tht sylleptic rnching occurred further from the shoot pex in Pillr ecuse greter distnce ws needed for the uxin:cytokinin rtio to ecome sufficiently low. Roots re elieved to e significnt source of cytokinin. In pech, removl of 50% of the rooting re inhiited lterl shoot production; however, this ws overcome y pplictions of enzyldenine, synthetic cytokinin (Richrds nd Rowe, 1977). Pillr trees were shown to hve decresed rooting re compred to stndrd trees (Tworkoski nd Scorz, 2001), which therefore ws hypothesized to e the cuse of lower cytokinin content in Pillr trees nd, in turn, less sylleptic rnching compred to stndrd trees (Tworkoski et l., 2006). Pillr shoots were more vigorous in the upper third of the cnopy, with twice the shoot length nd lterl rnches in the upper compred to the ottom third. Auxin:cytokinin rtios did not chnge throughout the cnopy of Pillr trees, ut sylleptic rnching ws greter in the upper third (Tworkoski et l., 2006). Tworkoski et l. concluded tht uxin:cytokinin rtios exert limited control over sylleptic rnching when there isn t strong competition etween sinks or limited resource vilility. Conclusions Renewl of fruiting sites is necessry for production of high qulity sweet cherries throughout the life of n orchrd. Trditionl nnul renewl is done y removing few of the 12

24 lrgest rnches in the cnopy. This cretes growth resource competition in the tree etween fruiting sites nd vegettive renewl sites; in high density orchrds utilizing dwrfing rootstocks, this competition decreses the growth of renewl sites. Whole tree renewl elimintes this competition, trnsitioning the tree to only vegettive growth nd development. Apicl dominnce controls rnching through the production of uxin, which plys n indirect role in mintining xillry ud prdormncy (Leyser, 2003). Removl of the shoot pex hlts the production of uxin, nd ltent or xillry dormnt uds hve the potentil to ecome ctivted nd develop into rnch. Epicormic rnching is regenertive response of woody plnts to refill cnopy spce from epicormic uds fter the ud hs een relesed from prdormncy. Removl of greter portion of the cnopy results in incresed epicormic rnching (O Hr nd Berrill, 2009). Sylleptic rnches develop in the yer tht their prent rnch forms. Sylleptic rnching is lso under the influence of picl dominnce nd occurs when uxin:cytokinin rtios re low (Tworkoski et l., 2006). 13

25 Yer 1 Figure 1.1- First yer of growth: rnch with single leves t ech node (Long et l., 2015). Yer 1 Yer 2 Figure 1.2- Second yer of growth: sl fruit, vegettive spurs long one yer old growth, nd nnul extension of new growth (Long et l., 2015). Yer 3 Yer 2 Yer 1 Figure 1.3- Third yer of growth: fruiting spurs long two-yer-old growth, sl fruit on one yer old growth, followed y vegettive spurs, nd finlly nother section of new growth (Long et l., 2015). 14

26 Figure 1.4- Scnning electronic microscope imge of smll preventitious epicormic uds without secondry ud primordi (Fontine et l., 1999). 15

27 Figure 1.5- Lrge preventitious epicormic ud: SEM of lrge primry ud in the center, surrounded y secondry ud primordi (Fontine et l., 1999). 16

28 LITERATURE CITED 17

29 LITERATURE CITED Ayl, M. nd Lng, G. A. (2017). Morphology, Cropping Physiology, nd Cnopy Trining, p In: Quero-Grci, J., Iezzoni, A., Pulwsk, J., nd Lng, G. A. (Eds.). Cherries: Botny, Production nd Uses. CABI. Brhm, R. R., nd Kellison, R. C. (1987). Suppressed uds in yellow-poplr. Journl of the Elish Mitchell Scientific Society, Brown, C.L Primry Growth. In: Zimmermn, M. H., nd Brown, C. L. (1971). Trees: Structure nd Function. New York, USA, Springer-Verlg.. Büsgen, M. nd Münch, E. (1929). The Structure nd Life of Forest Trees. John Wiley nd Sons Inc., New York, NY, USA. 436 pp. Burrows, G. E. (1989). Developmentl ntomy of xillry meristems of Arucri cunninghmii relesed from picl dominnce following shoot pex decpittion in vitro nd in vivo. Botnicl Gzette, Burrows, G. E. (2000). An ntomicl study of epicormic ud strnd structure in Euclyptus cldoclyx (Myrtcee). Austrlin Journl of Botny, 48(2), Burrows, G. E. (2008). Syncrpi nd Tristniopsis (Myrtcee) possess specilised fire-resistnt epicormic structures. Austrlin Journl of Botny, 56(3), Cline, M. G. (1996). Exogenous uxin effects on lterl ud outgrowth in decpitted shoots. Annls of Botny, 78(2), Cline, M. G. (2000). Execution of the uxin replcement picl dominnce experiment in temperte woody species. Americn Journl of Botny, 87(2), Cline, M. G., nd Dong-Il, K. I. M. (2002). A preliminry investigtion of the role of uxin nd cytokinin in sylleptic rnching of three hyrid poplr clones exhiiting contrsting degrees of sylleptic rnching. Annls of Botny, 90(3), Colin, F., Ducousso, A., nd Fontine, F. (2010). Epicormics in 13-yer-old Quercus petre: smll effect of provennce nd lrge influence of rnches nd growth unit limits. Annls of Forest Science, 67(3), 312. Cooper-Ellis, S., Foster, D. R., Crlton, G., nd Lezerg, A. (1999). Forest response to ctstrophic wind: results from n experimentl hurricne. Ecology, 80(8), Fink, S. (1983). The occurrence of dventitious nd preventitious uds within the rk of some temperte nd tropicl trees. Americn Journl of Botny,

30 Fink, S. (1999). Pthologicl nd regenertive plnt ntomy. Geruder Borntreger Verlgsuchhndlung. Fontine, F., Druelle, J. L., Clément, C., Burrus, M., nd Audrn, J. C. (1998). Ontogeny of proventitious epicormic uds in Quercus petre. I. In the 5 yers following initition. Trees, 13(1), Fontine, F., Kiefer, E., Clément, C., Burrus, M., nd Druelle, J. L. (1999). Ontogeny of the proventitious epicormic uds in Quercus petre. Trees-Structure nd Function, 14(2), Gordon, D., Rosti, A., Dmino, C., nd DeJong, T. M. (2006). Sesonl effects of light exposure, temperture, trunk growth nd plnt crohydrte sttus on the initition nd growth of epicormic shoots in Prunus persic. Journl of Horticulturl Science nd Biotechnology, 81(3), Gruer, F. (1994). Morphology of coniferous trees: possile effects of soil cidifiction on the morphology of Norwy spruce nd Silver fir. Effects of Acid Rin on Forest Processes, Hrmer, R. (1991). The Effect of Bud Position on Brnch Growth nd Bud Ascission in Quercus petre (Mtt.) Liel. Annls of Botny, 67(5), Hillmn, J. R., Mth, V. B., nd Medlow, G. C. (1977). Apicl dominnce nd the levels of indole cetic cid in Phseolus lterl uds. Plnt, 134(2), Kuppi, A., Rinne, P., nd Ferm, A. (1987). Initition, structure nd sprouting of dormnt sl uds in Betul puescens. Flor, 179(1), Kormnik, P. P., nd Brown, C. L. (1969). Origin nd development of epicormic rnches in sweetgum. US For. Serv. Res. Pp. Sthest For. Exp. St., No. SE-54, 17pp. [For. Astr. 31 (1970) No ] Buds, Hmmel (PMBD, ). Lng, G. A. (2000). Precocious, dwrfing, nd productive how will new cherry rootstocks impct the sweet cherry industry? HortTechnology, 10(4), Lng, G. A., Olmsted, J. W., nd Whiting, M. D. (2004). Sweet cherry fruit distriution nd lef popultions: modeling cnopy dynmics nd mngement strtegies. Act Horticulture, Leyser, O. (2003). Regultion of shoot rnching y uxin. Trends in Plnt Science, 8(11), Ljung, K., Bhlero, R. P., nd Snderg, G. (2001). Sites nd homeosttic control of uxin iosynthesis in Aridopsis during vegettive growth. The Plnt Journl, 28(4),

31 Long, L. E., Lng, G. A., Whiting, M. D., nd Muscchi, S. (2015). Cherry trining systems. Pcific Northwest Extension. Oregon Stte University. University of Idho. Wshington Stte University. Mguylo, K., Lng, G. A., nd Perry, R. L. (2002, August). Rootstocks genotype ffects flower distriution nd density of 'Hedelfinger'sweet cherry nd'montmorency'sour cherry. Act Horticulture, 636 (pp ). Michign Ag Council. (2016). Michign Cherries - Michign Agriculture. Retrieved Octoer 17, 2017, from Nicolini, E., Chnson, B., nd Bonne, F. (2001). Stem growth nd epicormic rnch formtion in understorey eech trees (Fgus sylvtic L.). Annls of Botny, 87(6), O'Hr, K. L., nd Berrill, J. P. (2009). Epicormic sprout development in pruned cost redwood: pruning severity, genotype, nd sprouting chrcteristics. Annls of Forest Science, 66(4), 1-9. Piene, H., nd Eveleigh, E. S. (1996). Spruce udworm defolition in young lsm fir: the green tree phenomenon. The Cndin Entomologist, 128(06), Perry, R., Lng, G., Andersen, R., Anderson, L., Azrenko, A., Fcteu, T.,... nd Rom, C. (1997, July). Performnce of the NC-140 cherry rootstock trils in North Americ Act Horticulture, 468 (pp ). Richrds, D., nd Rowe, R. N. (1977). Effects of root restriction, root pruning nd 6- enzylminopurine on the growth of pech seedlings. Annls of Botny, 41(4), Roinson, T. L., DeMrree, A. M., nd Hoying, S. A. (2004, June). An economic comprison of five high density pple plnting systems. In Act Horticulture, 732 (pp ). Schs, T., nd Thimnn, K. V. (1967). The role of uxins nd cytokinins in the relese of uds from dominnce. Americn Journl of Botny, Scrsci-Mugnozz, G. E., Hinckley, T. M., Stettler, R. F., Heilmn, P. E., nd Isernds, J. G. (1999). Production physiology nd morphology of Populus species nd their hyrids grown under short rottion. III. Sesonl cron lloction ptterns from rnches. Cndin Journl of Forest Reserch, 29(9), Schetzl, R. (n.d.). Fruit Production. Retrieved Decemer 03, 2017, from Sorefn, K., Booker, J., Hurogné, K., Goussot, M., Binridge, K., Foo, E.,... nd Leyser, O. (2003). MAX4 nd RMS1 re orthologous dioxygense-like genes tht regulte shoot rnching in Aridopsis nd pe. Genes & Development, 17(12), Spth H. (1912). Der Johnnistriee. Berlin: Prey. 20

32 Stone, E. L., nd Stone, M. H. (1943). "Dormnt" versus "Adventitious" uds. Science, 98(2533), Sunderg, B., nd Uggl, C. (1998). Origin nd dynmics of indolecetic cid under polr trnsport in Pinus sylvestris. Physiologi Plntrum, 104(1), Tworkoski, T., Miller, S., nd Scorz, R. (2006). Reltionship of pruning nd growth morphology with hormone rtios in shoots of pillr nd stndrd pech trees. Journl of Plnt Growth Regultion, 25(2), Wignll, T. A., nd Browning, G. (1988). Epicormic Bud Development in Quercus rour L. Studies of Endogenous IAA, ABA, IAA Polr Trnsport nd Wter Potentil in Cmil Tissues10. Journl of Experimentl Botny, 39(12), Wignll, T. A., Browning, G., nd Mckenzie, K. A. D. (1987). The physiology of epicormic ud emergence in Pedunculte Ok (Quercus rour L.) Responses to prtil notch girdling in thinned nd unthinned stnds. Forestry: An Interntionl Journl of Forest Reserch, 60(1),

33 CHAPTER 2: WHOLE TREE RENEWAL REGENERATES FRUITING STRUCTURES QUICKLY IN MATURE ORCHARDS Introduction The lrgest nd highest qulity sweet cherries re orne on sl flower uds of one-yerold rnches nd on young spurs. Annul prtil renewl (APR) of ~10-20% of the cnopy, y removing the lrgest one to severl rnches during dormncy nd llowing for spring regrowth from ltent or epicormic uds uried eneth the rk, mintins young fruiting sites (Long et l., 2015). APR pruning cretes competition in the tree for photossimiltes etween sinks, i.e., fruiting sites nd vegettive renewl sites (G.A. Lng, personl communiction). In high density ( trees per h -1 ) sweet cherry orchrds, precocious, dwrfing rootstocks re utilized to control tree vigor nd otin high productivity (Lng, 2000; Perry et l., 1997). Compred to vigorous rootstocks, dwrfing rootstocks direct greter percentge of their photossimiltes to fruit production rther thn vegettive growth (Atkinson nd Else, 2001). This cn result in inconsistent regrowth following APR pruning, mking it difficult to mintin n optiml lnce of rnch ges in the cnopy. Modern orchrds hve moved wy from trditionl tree spcing ( trees per h -1 ) with lrge, complex trees nd wide rows. High density orchrds utilizing dwrfing rootstocks come into full production quickly (5-7 yers) compred to trditionl systems (8-12 yers) nd often utilize simplified trining systems with nrrow fruiting wlls tht increse light penetrtion nd lor efficiency, leding to greter returns on investment for growers. Smll, simplified cnopies hve mde it possile to utilize protective plstic covers in sweet cherry production, such s high tunnels nd row covers. High rtes of wter uptke fter rin through either the fruit cuticle or the tree root system cn induce crcking of sweet cherries (Meshm et 22

34 l., 2009); covering systems cn reduce or eliminte this loss, s well s limit disese nd improve frost protection. Auxin (indole-3-ceetic cid) produced in the shoot pex nd newly formed leves (Ljung et l., 2001) moves sipetlly through polr trnsport (Wignll et l., 1987; Sunderg nd Uggl, 1998) nd inhiits outgrowth of xillry meristems through n indirect mechnism (Leyser, 2003). In woody plnts, xillry meristems tht mintin prdormncy under picl dominnce eventully ecome engulfed y rdil growth of the rnch, persisting just eneth the rk (Büsgen nd Münch, 1929; Stone nd Stone, 1943). Removl of the shoot pex stops the inhiitory effects of uxin nd cytokinin trnsport into uds is incresed, promoting ud outgrowth (Schs nd Thimnn, 1967). In the cse of epicormic uds, this outgrowth cretes n epicormic rnch. Epicormic rnching refills the cnopy fter dmge or stress. Fire (Burrows, 2008), insect defolition (Piene nd Eveleigh, 1996), wind dmge (Cooper-Ellis et l., 1999), competition (Nicolini et l., 2001), nd pruning (O Hr nd Berrill, 2009) hve ll een shown to initite epicormic rnching. Incresing the proportion of the cnopy sujected to pruning results in higher numer nd more vigorous epicormic rnches produced (O Hr nd Berrill, 2009). Trees grown under no light were shown to hve 25% reduction in epicormic rnching (Gordon et l., 2006). Pruning initites epicormic rnching y removing the correltive inhiition of uxin eing synthesized s well s y incresing light exposure. Sylleptic rnches sprout in the sme yer tht their prent rnch origintes (Spth, 1912). The propensity to produce sylleptic rnches is relted to uxin sensitivity; greter insensitivity to uxin increses sylleptic rnching (Cline nd Dong-Il, 2002). Lower uxin-tocytokinin rtios resulted in more sylleptic rnching in pech; Pillr trees exhiited stronger 23

35 picl dominnce with more upright growth hit thn Stndrd, which hd lower uxin to cytokinin rtio nd more sylleptic rnching (Tworkoski et l., 2006). Auxin-to-cytokinin rtios hd less of n effect on sylleptic rnching when competition etween sinks ws less. In Pillr, shoots in the upper third were more vigorous nd produced more sylleptic rnches, lthough uxin-to-cytokinin rtios were constnt throughout the tree (Tworkoski et l., 2006). Whole tree renewl (WTR; the removl of ll fruiting portions of the cnopy, leving only the primry vegettive structure) elimintes competition in the cnopy etween fruiting nd vegettive renewl sites. In contrst to APR pruning of every tree in the orchrd every yer, the concept of WTR pruning could e pplied to the entire orchrd every 6-7 yers or to only out 15% of the trees in the orchrd every yer. The ojective of this study ws to document nd nlyze the initil WTR regrowth response of vrious high density sweet cherry trining systems on rootstocks tht differ in vigor, nd determine how quickly cnopy structure nd fruiting sites re regenerted fter WTR. Mterils nd Methods Site nd Plnt Mteril This study ws conducted t the Michign Stte University Clrksville Reserch Center (Clrksville, MI, lt. 42.8ºN, long. 85.2ºW) within the NC-140 sweet cherry trining systems x rootstock tril, plnted in WTR pruning ws imposed on irrigted eight-yer-old trees of the cultivr Benton grfted onto three rootstocks of differing vigor: Gisel 3, dwrfing; Gisel 5, semi-dwrfing; nd Gisel 6, semi-vigorous, growing in corse-lomy, mixed, mesic Typic Hpludlf soil of the Lpeer series (Soil Survey Stff, Nturl Resources Conservtion Service, United Sttes Deprtment of Agriculture, 2017). Four cnopy trining systems were studied on ech of these rootstocks: stndrd centrl leder tree, Tll Spindle Axe (TSA); plnr centrl 24

36 leder tree Super Slender Axe (SSA); multiple leder ush, Kym Green Bush (KGB); nd trellised nrrow plnr fruiting wll, Upright Fruiting Offshoots (UFO), which hs multiple leders rising from horizontl cordon-like trunk plnted t 45 ngle (fig. 2.1). The only exception ws the lck of n SSA x Gi5 comintion in the tril; therefore, there were 11 trining system y rootstock comintions. Between row spcing is 3.5 m. Within row spcing is 1.5 m etween trees for TSA, UFO nd KGB trees nd 0.75 m for SSA trees. Ech of these 11 trining system y rootstock tretment comintions mke up repliction, occupying two rows in the orchrd. TSA, UFO, nd KGB ech hve four trees per tretment group, SSA t twice the density hs eight trees per tretment group. One tree in ech of these tretment groups ws used for whole tree renewl, the other trees re nnully renewed ech yer. A gurd tree, either the cultivr Attik on Gi6 or NY119 on Gisel 12, trined to TSA seprtes tretment groups. Whole Tree Renewl Pruning WTR pruning ws imposed t full loom, April 27, Preliminry reserch (G.A. Lng, personl communiction) found the est regrowth response when WTR pruning ws imposed t full loom, compred to dormnt, green tip ud swell or petl fll. WTR pruning removed ll lterl fruiting rnches (TSA, SSA) or upright fruiting leders (UFO, KGB), leving ~10 cm stus from the centrl trunk (TSA, SSA), horizontl cordon (UFO), or se of the ush (KGB). After renewl cuts were mde, epicormic rnches were llowed to develop uninhiited throughout the 2016 growing seson. Initil Regrowth Mesurements Initil regrowth dt ws collected in erly winter (Decemer 15-Jnury 5), once leves hd scised nd the trees hd gone dormnt (Decemer 2016). Totl numer of primry renewl rnches, length of ech primry renewl rnch, nd numer of sylleptic rnches per primry 25

37 rnch ws ll mesured once in the field. Length mesurements were done using tpe mesure, from the se of the rnch to the terminl ud. The TSA nd SSA centrl leder nd the UFO cordon leder were mrked into thirds (distl, middle, nd proximl) to quntify renewl shoot distriution nd uniformity. The KGB ws not le to e split into thirds ecuse ll of the leders were cut ck to reltively similr points of origin in the se of the ush Mintennce Pruning In spring 2017, the WTR trees were pruned following stndrd guidelines for estlishment nd mintennce of ech trining system s descried in Long et l. (2015). For the TSA trees, renewl shoots tht were too vigorous, too upright, too pendent, or overlpping were removed, nd lterl shoots tht were retined were hed-pruned to remove 15-25% of their length nd stimulte secondry lterl rnching. All sylleptic shoots were retined unless they were too upright, pendent, or overlpping. For the SSA trees, ll renewl shoots were shortpruned (hed-pruned to remove ll ut the most sl single flower uds plus 1-3 sl vegettive uds). For the UFO trees, verticlly-oriented renewl shoots were thinned nd tied to the trellis out every 8 inches, nd horizontl or pendent renewl shoots were removed, s were ny sylleptic rnches. For KGB trees, verticlly-oriented renewl shoots were retined unless they were excessively vigorous, nd ny sylleptic rnches were removed. Horizontl or pendent renewl shoots were removed s well. Cnopy Volume Mesurements In August 2017, following the second seson of regrowth nd stndrd summer pruning, the cnopy volumes of WTR trees were compred to those of djcent APR pruned trees (those tht hve the lrgest one to severl rnches removed every yer). Summer pruning composed of posthrvest hedging, leving ~25 cm of new est-west lterl growth on UFO nd KGB upright 26

38 leders, or leving ~60 to ~90 cm (mesured from the centrl leder) of horizontl est-west lterl rnch growth on SSA nd TSA centrl leders, respectively. After this mid-summer hedging, little vegettive regrowth ws expected. Therefore, August cnopy mesurements llowed comprison of the cnopy volumes s significnt spur fruiting is expected to egin the third yer fter WTR (2018). Within row (N-S) nd cross row (E-W) cnopy spred mesurements were tken t 0.75 m, 1.5 m, nd 2.25 m from the ground cnopy; with mesuring tpe on August 8, Cnopy spred ws mesured t ech height y mesuring from the end of the furthest reching rnch on one side of the cnopy to the furthest reching rnch on the opposite side. For exmple, t the 0.75-meter height the within row spred ws the distnce etween the northern most rnch nd the southernmost; cross row ws distnce etween estern nd westernmost rnch t 0.75 meters from the ground. Covering System Ech trining system y rootstock comintion ws replicted under two different covering systems: CRAVO (Brntford, Ontrio) nd VOEN (Berg, Germny). The CRAVO is plstic-covered structure with progrmmle retrctle roof nd north-south sides tht generlly remin opens during the summer except when it rins, t which time the roof closes utomticlly. In lte winter nd erly spring, the sides nd roof of the CRAVO re closed to cpture solr rdition tht promotes erlier loom, nd propne convection heters (80,000 BTU Mr. Heter, Enerco, Clevelnd, OH) re plced inside to protect from spring frosts. The VOEN is plstic-nd-net rin cover tht opens over the tree row nd clips together in the lleywy. VOEN covers were opened fter fruit set in My. 27

39 Dt Anlysis nd Plot Design Being prt of the NC-140 sweet cherry rootstock tril, the greter tril is lid out in completely rndomized lock design, locking sed on CRAVO nd VOEN; with two rows representing repliction, hving ll 11 trining system y rootstock comintions. The NC-140 tril utilizes four trees per trining system y rootstock tretment for TSA, UFO, nd KGB on ll three rootstocks; SSA eing plnted t twice the density, hs eight trees per tretment. A single gurd tree, either the cultivr Attik on Gi6 or NY 119 on Gi12 rootstock trined to TSA seprtes tretments. Whole tree renewl ws imposed on one tree per tretment, the outside tree in the group of four or eight. Three replictions were under the CRAVO nd two were under the VOEN covers, just west of the CRAVO plots. Ech repliction consisted of single tree in ech loction, therefore, n=33 for CRAVO nd n=22 for VOEN. For initil regrowth dt, two-wy ANOVAs were determined using Tukey s LSD, significnce t p 0.05 (PROC MIXED, SAS version 9.3, SAS Institute, Cry, NC). Due to this study eing unlnced, missing the SSA x Gi5 comintion, nlyses etween rootstocks were mde without ny SSA dt, nd comprisons etween trining systems were mde without ny dt from Gi5. Furthermore, ecuse the KGB permnent tree structure could not e split up in thirds, comprisons were mde on whole tree sis with KGB nd KGB dt were left out when compring cnopy thirds. CRAVO nd VOEN dt were nlyzed seprtely nd therefore hve their own ANOVA tle nd grphs for ech initil response mesurement. Due to the vried cnopy rchitectures, cnopy spred ws clculted y verging innd etween-row mesurements t ech height (0.75, 1.5, nd 2.25 m). Cnopy spred ws ssessed t ech height using one-wy ANOVAs etween WTR nd APR trees for ech trining system y rootstock comintion. Loction ws included in ANOVAs, nlyzing CRAVO nd 28

40 VOEN together. ANOVAs nd Tukey LSD were clculted t significnce of p 0.05 in RStudio, version (Vienn, Austri). Results Cnopy Volume After two sesons of regrowth nd stndrd cnopy mngement following WTR pruning, ll trining system x rootstock comintions hd completely refilled their llotted orchrd spce (s mesured ginst respective APR tree cnopy spreds) except for the 0.75 m height of cnopy spred for SSA x Gi3 nd the 2.25 m cnopy height for KGB x ll rootstocks (figs ). WTR-pruned TSA nd UFO trees completely refilled their spce. Cnopy spred vried it y loction, ut the comprtive trend etween WTR versus APR pruning remined the sme in oth the CRAVO- nd VOEN-covered orchrds (figs. 2.2, 2.3, nd 2.5). Initil Growth Dt Regrding the initil regrowth dt, the numer of renewl shoots ws greter in the distl section of the cnopy cross ll rootstocks nd trining systems nlyzed y cnopy proportion (TSA, SSA, UFO); there were no differences in renewl shoot numer etween middle nd proximl sections. This trend ws the sme etween CRAVO nd VOEN (figs. 2.6 nd 2.7). On whole tree sis, Gi6 responded with more replcement shoots thn Gi5 nd Gi3 under the CRAVO (fig. 2.8), ut there were no rootstock differences for trees grown under the VOEN (tle 2.1). Under the CRAVO, TSA nd SSA trees hd greter numer of new shoots compred to KGB nd UFO trees (fig. 2.9A). TSA trees hd more new shoots thn ny of the other systems under the VOEN (fig. 2.9B). The three-wy interction term ws significnt for cnopy section y rootstock y system for verge shoot length cross ll rootstocks nd systems in the CRAVO (p=0.0003) nd the 29

41 VOEN (p=0.0361) orchrds. The only discernle trend ws tht UFO generlly hd longer shoots, regrdless of rootstock or cnopy section thn did TSA nd SSA in oth loctions (figs nd 2.11). This trend remined when nlyzing the whole tree over ll rootstocks: UFO nd KGB trees hd the longest verge new shoot length, followed y TSA, nd SSA trees hd the lest in the CRAVO; under the VOEN, the KGB trees hd greter verge shoot lengths thn did UFO trees, which were greter thn TSA, nd SSA once gin hd the shortest shoot lengths (figs. 2.12A nd 2.12B). In the CRAVO, trees on Gi6 nd Gi5 hd longer renewl shoot lengths thn trees on Gi3 (fig. 2.13A). However, under the VOEN, new shoot length for trees on Gi6 ws greter thn those on Gi5, nd trees on Gi3 were not sttisticlly different from either Gi6 or Gi5 (fig. 2.13B). The vriility of sylleptic rnching ws wide (fig. 2.20). Compring the cnopy sections, the distl third hd more sylleptic rnching thn the middle nd proximl sections in the CRAVO when SSA dt ws omitted (fig. 2.14). However, in the VOEN, the three-wy interction term for system y rootstock y cnopy section ws significnt; there ws no oservle trend in this dt (fig. 2.15). Removing the Gi5 dt, rootstock y cnopy section ws significnt in the CRAVO nd system y cnopy section ws significnt in the VOEN. In the CRAVO, the distl cnopy section of trees on Gi6 hd more sylleptic rnching thn the middle nd proximl sections, s well s ll cnopy sections of trees on Gi3 (fig. 2.16). The VOEN dt showed the middle cnopy section of UFO trees hd greter sylleptic rnching thn the distl nd proximl sections, s well s ll cnopy sections of TSA nd SSA trees (fig. 2.17). When compring sylleptic rnching cross rootstocks, there were no differences in either the CRAVO or the VOEN when the SSA dt ws omitted (tles 2.2 nd 2.3). When compring sylleptic rnching cross ll four trining systems (requiring the omission of the Gi5 dt), results in the 30

42 CRAVO nd VOEN differed slightly: the KGB nd UFO trees hd more sylleptic rnching thn TSA nd SSA trees in the CRAVO (fig. 2.17A), while KGB tree sylleptic rnching ws greter thn tht for TSA, SSA, nd UFO trees in the VOEN (fig. 2.17B). While sylleptic rnching ws quite vrile, there ws generl trend tht the longest primry renewl shoots produced the most sylleptic rnches (fig. 2.20). Exmining the dt s qurtiles revels tht the longest 25% of renewl rnches hd the gretest sylleptic rnch vriility nd the widest distriution (fig. 2.21). Discussion The cnopy spred dt show tht WTR pruning of KGB trees did not completely refill their upper cnopy volume within two growing sesons (fig. 2.5). This represents significnt fruiting re. While KGB nd UFO trees hd the longest verge new shoot length on whole tree sis (figs. 2.12A nd 2.12B), KGB renewl shoots strted reltively close to the ground nd hd the gretest verticl nd horizontl cnopy volume to e refilled. UFO trees hd similr verticl cnopy spce to refill, ut the structured plnr nture of UFO cnopy provides much smller horizontl cnopy volume per tree, which ws redily refilled within two sesons. The inility for KGB trees to dequtely refill their cnopy volume within two sesons indictes tht recovery of full fruiting potentil will e delyed compred to the other trining systems. The lowest cnopy spred height (0.75 m) ws the only prt of the SSA cnopy on Gi3 tht ws not completely refilled within two sesons following WTR pruning (fig. 2.2). These re the wekest trees in the tril, with the gretest root competition from close spcing, the most dwrfing rootstock, the smllest trunk cross-sectionl re (fig. 2.19), nd consequently the smllest storge potentil for growth reserves. These fctors ssocited with decresed vigor likely resulted in the proximl cnopy section of SSA on Gi3 hving some of the shortest 31

43 renewl shoot lengths (fig. 2.11A nd 2.11B) nd, like the KGB, delyed recovery of full fruiting potentil. This scenrio is contrry to previous study tht showed trees of decresed vigor produced more epicormic rnches (O Hr nd Vlppil, 2000). However, this study did not prune trees s severely s WTR, nd pruning severity hs een positively correlted with epicormic rnching (O Hr nd Berrill, 2009). Therefore, under n extreme imposed stress such s WTR pruning, vigor might ply more importnt role in epicormic development thn when decresed vigor is the min stress, s in O Hr nd Vlppil (2000). Like KGB trees, TSA trees lso hve complex, 3-dimensionl cnopy. However, mintining the length of the TSA centrl leder provides gret potentil numer of epicormic uds or epicormic potentil (Fontine et l., 2001), nd the cnopy volume to e refilled fter WTR pruning is primrily horizontl rther thn verticl. The greter epicormic potentil of TSA trees resulted in more renewl rnches initited. Likewise, the centrl leder SSA trees hve similr epicormic potentil nd therefore comprle renewl rnch numers initited in the CRAVO. However, SSA trees hd fewer renewl rnches sprout under the VOEN (figs. 2.9A nd 2.9B). It is uncler why this inconsistency exists; it my e dt rtifct due to only two replictions in the VOEN, or possile outlier SSA dt relted to n extensive cteril cnker infection when the trees were four yers old (2012) tht ws more severe in the VOEN plot compred to the CRAVO plot. While the numer of sylleptic rnches per renewl shoot vried gretly y primry renewl rnch length, there ws generl trend of longer renewl rnches producing more syllepetic rnches (fig. 2.20). The longest 24% of primry renewl rnches resulted in the widest distriution of sylleptic rnches (fig. 2.21). The most vigorous renewl rnches producing more syllepetic rnches is contrry to the results of Cline nd Don-Il (2002), who 32

44 found tht the most vigorous of three poplr hyrids hd the gretest suppression of sylleptic rnches fter synthetic uxin ws pplied following shoot pex decpittion. Significnt differences etween trining systems for numer of sylleptic rnches lmost mirrored those of length per renewl rnch. In the CRAVO, KGB nd UFO trees hd the longest length nd most sylleptic rnching. In the VOEN, UFO shoot length ws less thn KGB, s ws the numer of sylleptic rnches produced (figs. 2.12A, 2.12B, 2.18A, 2.18B). This trend supports the conclusion tht the most vigorous renewl shoots resulted in the highest numer of sylleptic rnches. This is counter to the report of Tworkoski et l. (2006), who found tht etween two rchitecturlly distinct pech genotypes, the one with more upright growth displyed greter picl dominnce nd less sylleptic rnching. In our current study, the renewl shoots of the UFO nd KGB trees re trined to fill verticl spce, yet these hd more sylleptic rnching thn the lterl renewl shoot growth of TSA nd SSA trees. Sylleptic rnching my e positive or negtive response, depending on sweet cherry trining system. KGB nd UFO trees crop primrily on spurs on upright leders; sylleptic rnch occupies node tht eventully would hve ecome fruiting spur, ultimtely resulting insted in lind wood tht decreses fruiting potentil. Conversely, some sylleptic rnches on TSA nd SSA trees cn e used to replce horizontl fruiting structure, refilling cnopy volume more quickly. However, this study hs showed tht sylleptic rnches re chrcteristic of the more vigorous renewl rnches, which typiclly re unfruitful. It is therefore questionle whether sylleptic rnches re positive or negtive response for TSA nd SSA trees; further flowering dt from spring 2018 will ddress this question. The extreme shock imposed y WTR pruning must e considered when compring our results on sylleptic rnching to pst studies. Removing ll rnches removes the sites of uxin 33

45 synthesis (Ljung et l., 2001). Cytokinin production is incresed fter eliminting the inhiitory effects of uxin on cytokinin synthesis nd export from roots (Leyser, 2003). WTR trees re very likely in stte where uxin:cytokinin rtios re low, which hs een correlted with sylleptic rnching (Tworkoski et l., 2006). TSA nd SSA trees hd more renewl shoots thn UFO nd KGB trees (fig. 2.9A nd 2.9B), nd therefore it s likely tht higher uxin content nd higher uxin-to-cytokinin rtios cuse less sylleptic rnching in the less vigorous, lterlly growing TSA nd SSA tree trining systems. CRAVO nd VOEN dt ws nlyzed seprtely for simplicity of grphs, there were mny instnces when the loction effect ws significnt. This then mde instnces where the three wy interction ws significnt, system y rootstock y permnent structure section, mking 18 different tretment groups; more complicted when it ws four wy interction, giving 36 different tretment groups in the sme grph. Since we weren t prticulrly interested in differences in covering system, these dt were nlyzed nd plotted seprtely. This interction could simply e due to there eing only two replictions in the VOEN, three in the CRAVO, nd hving n outlier tht is influencing the dt more. However, there re lso environmentl differences tht exist etween these two covering systems. Looking just t sylleptic rnching for ll four trining systems verged over Gi3 nd Gi6 there ws sylleptic rnch per renewl rnch increse on KGB, TSA, nd SSA trees grown in the VOEN (fig. 2.18B) thn CRAVO (fig. 2.18A); UFO remined similr in oth loctions t ~1.7 sylleptic rnches per primry renewl rnch. This increse in sylleptic rnching in the VOEN might e explined y those covers remining over the trees throughout the growing seson, while the CRAVO covers only close when it egins to rin. These VOEN covers produce shde, leding to lower light environments in the VOEN thn CRAVO. Phototropins, specificlly Cryptochromes 34

46 CRY1, CRY2, nd CRY3 hve een shown to e upregulted in response to low light in Aridopsis thlin (Tkemiy et l., 2005). It is elieved tht ud urst is promoted y CRY1 nd CRY2 protoreceptors promoting expression of ELONGATED HYPOCOTOL5 (HY5) (Signorelli et l., 2017). HY5 genes re involed in chlorophyll iosynthesis nd light hrvesting (Eerhrd et l., 2008). The lower light conditions in the VOEN could e resulting in n upregultion of CRY genes nd in turn HY5 leding to greter sylleptic rnching in VOEN trees compred to trees in the CRAVO. Conclusions WTR pruning hs een shown to quickly refill sweet cherry cnopies cross multiple cnopy rchitectures. The resulting replcement cnopy fruiting structure is more uniform thn tht of APR-pruned trees, which is comprised of mix of fruiting structures of vrious ges. KGB trees hve the gretest cnopy volume per tree nd ws the only trining system, cross ll rootstocks, tht did not completely refill its cnopy volume within two sesons. Therefore, recovery of KGB fruiting potentil my require n extr yer compred to TSA, SSA, nd UFO trees. The numer of renewl rnches initited nd the verge length per renewl shoot were inversely relted TSA nd SSA initited more rnches, ut hd shorter verge renewl shoot length. Sylleptic rnching ws highly vrile, ut tended to e greter in more vigorous renewl shoots. Further reserch is needed to confirm the timing of complete recovery of fruiting potentil, s well s to understnd where new renewl shoots re most likely to rise. 35

47 Figure 2.1- Digrm of ech trining system used in the study. Kym Green Bush (KGB), Tll Spindle Axe (TSA), Super Slender Axe (SSA), nd Upright Fruiting Offshoots (UFO). Averge Cnopy Spred (m) overll CRAVO VOEN CRAVO VOEN Gi3 WTR APR Gi6 Figure 2.2- SSA on Gi3 nd Gi6 whole tree renewl (WTR) cnopy verge spred versus spred of nnul prtil renewl (APR) trees t 0.75, 1.5, nd 2.25 meters in the cnopy. Cnopy spred verged over CRAVO nd VOEN t Michign Stte University s Clrksville Reserch Center, except where noted s CRAVO or VOEN. Lowercse letters seprte mens etween WTR nd APR t ech height tested using Tukey LSD were clculted t significnce of p

48 Averge Cnopy Spred (m) overll overll CRAVO VOEN overll Gi3 Gi5 Gi6 WTR APR Figure 2.3- TSA on Gi3, Gi5, nd Gi6 whole tree renewl (WTR) cnopy verge spred versus spred of nnul prtil renewl (APR) trees t 0.75, 1.5, nd 2.25 meters in the cnopy. Cnopy spred verged over CRAVO nd VOEN t Michign Stte University s Clrksville Reserch Center, except where noted s CRAVO or VOEN. Lowercse letters seprte mens etween WTR nd APR t ech height tested using Tukey LSD were clculted t significnce of p Averge Cnopy Spred (m) overll Gi3 Gi5 Gi6 WTR APR Figure 2.4- UFO on Gi3, Gi5, nd Gi6 whole tree renewl (WTR) cnopy verge spred versus spred of nnul prtil renewl (APR) trees t 0.75, 1.5, nd 2.25 meters in the cnopy. Cnopy spred verged over CRAVO nd VOEN t Michign Stte University s Clrksville Reserch Center, except where noted s CRAVO or VOEN. Lowercse letters seprte mens etween WTR nd APR t ech height tested using Tukey LSD were clculted t significnce of p

49 Averge Cnopy Spred (m) overll CRAVO VOEN overll CRAVO VOEN overll Gi3 Gi5 Gi6 WTR APR Figure 2.5- KGB on Gi3, Gi5, nd Gi6 whole tree renewl (WTR) cnopy verge spred versus spred of nnul prtil renewl (APR) trees t 0.75, 1.5, nd 2.25 meters in the cnopy. Cnopy spred verged over CRAVO nd VOEN t Michign Stte University s Clrksville Reserch Center, except where noted s CRAVO or VOEN. Lowercse letters seprte mens etween WTR nd APR t ech height tested using Tukey LSD were clculted t significnce of p

50 numer of renewl rnches Figure 2.6A Distl Middle Proximl numer of renewl rnches Figure 2.6B Distl Middle Proximl Figure 2.6- Initil response numer of renewl rnches initited per permnent structure section, of TSA nd UFO grown on Gi3, Gi5, nd Gi6 fter whole tree renewl ws imposed. 5A- Brs re verge of 18 whole tree renewl trees grown in the CRAVO plus or minus stndrd error of the men. 5B- Brs re verge of 12 Whole tree renewl trees grown in the VOEN plus or minus stndrd of the men t Michign Stte University s Clrksville Reserch Center. Lowercse letters seprte mens compring cnopy sections, determined using Tukey s LSD, significnce t p

51 numer of renewl rnches Figure 2.7A Distl Middle Proximl numer of renewl rnches Figure 2.7B Distl Middle Proximl Figure 2.7- Initil response numer of renewl rnch per permnent structure section of TSA, SSA nd UFO grown on Gi3 nd Gi6 fter whole tree renewl ws imposed. 5A- Brs re verge of 18 whole tree renewl trees grown in the CRAVO plus or minus stndrd error of the men. 5B- Brs re verge of 12 Whole tree renewl trees grown in the VOEN plus or minus stndrd of the men t Michign Stte University s Clrksville Reserch Center. Lowercse letters seprte mens compring cnopy sections, determined using Tukey s LSD, significnce t p

52 numer of renewl rnches Gi3 Gi5 Gi6 Figure 2.8- Initil response numer of renewl rnch y rootstock verged over TSA, KGB nd UFO fter whole tree renewl ws imposed. Brs re n verge of 27 whole tree renewl trees grown in the CRAVO plus or minus stndrd error of the men t Michign Stte University s Clrksville Reserch Center. Lowercse letters seprte mens compring rootstocks, determined using Tukey s LSD, significnce t p numer of renewl rnches KGB TSA SSA UFO Figure 2.9A 41

53 Figure 2.9 (cont d) numer of renewl rnhes KGB TSA SSA UFO Figure 2.9B Figure 2.9- Initil response numer of renewl rnch y trining system, verged over Gi3 nd Gi6. 8A- Brs re verge of 21 whole tree renewl trees grown in the CRAVO plus or minus stndrd error of the men. 5B- Brs re verge of 14 Whole tree renewl trees grown in the VOEN plus or minus stndrd of the men t Michign Stte University s Clrksville Reserch Center. Lowercse letters seprte mens compring trining systems, determined using Tukey s LSD, significnce t p length per renewl rnch (m) f f f ef def def ef de ef ef c cd def def c cd 0 Distl Middle Proximl Distl Middle Proximl Distl Middle Proximl Distl Middle Proximl Distl Middle Proximl Distl Middle Proximl Gi3 Gi5 Gi6 Gi3 Gi5 Gi6 TSA UFO Figure 2.10A 42

54 Figure 2.10 (cont d) length per renewl rnch (m) de cd cd cd cde cd cd cd cd cd e Distl Middle Proximl Distl Middle Proximl Distl Middle Proximl Distl c Middle Proximl Distl cd Middle cd Proximl Distl Middle cd Proximl Gi3 Gi5 Gi6 Gi3 Gi5 Gi6 Figure 2.10B TSA UFO Figure Averge length per renewl rnch, one seson of growth fter whole tree renewl ws imposed. Three-wy interction: permnent structure section y rootstock y trining system. TSA nd UFO oth grown on Gi3, Gi5, nd Gi6. 9A-Brs re n verge per section of 3 whole tree renewl trees grown in the CRAVO plus or minus stndrd error of the men. 9B- Brs re n verge per cnopy section of 4 whole tree renewl trees grown in the VOEN plus or minus stndrd error of the men t Michign Stte University s Clrksville Reserch Center. Lowercse letters seprte mens compring the system y rootstock y section interction, determined using Tukey s LSD, significnce t p length per renewl rnch (m) ef ef ef Distl Middle Proximl de cd de Distl Middle Proximl Distl g fg efg ef fg Middle Proximl Distl Middle def def Gi3 Gi6 Gi3 Gi6 Gi3 Gi6 Proximl Distl Middle c Proximl Distl c Middle Proximl Figure 2.11A TSA SSA UFO 43

55 Figure 2.11 (cont d) cd cd 1.2 cde cdef cdef cdef cdef cdef e length per renewl rnch (m) Distl Middle Proximl Distl Middle Proximl Distl Middle Proximl def Distl Middle Proximl cde Gi3 Gi6 Gi3 Gi6 Gi3 Gi6 ef Distl Middle Proximl c Distl Middle cde Proximl Figure 2.11B TSA SSA UFO Figure Averge length per renewl rnch, one seson of growth fter whole tree renewl ws imposed. Three-wy interction: permnent structure section y rootstock y trining system. TSA, SSA nd UFO oth grown on Gi3 nd Gi6.. Three-wy interction: permnent structure section y rootstock y trining system. Without Gi5 dt. 10A-Brs re n verge per section of 3 whole tree renewl trees grown in the CRAVO plus or minus stndrd error of the men. 10B- Brs re n verge per cnopy section of 4 whole tree renewl trees grown in the VOEN plus or minus stndrd error of the men t Michign Stte University s Clrksville Reserch Center. Lowercse letters seprte mens compring the system y rootstock y section interction, determined using Tukey s LSD, significnce t p length per renewl rnch (m) Figure 2.12A c KGB TSA SSA UFO 44

56 Figure 2.12 (cont d) length per renewl rnch (m) Figure 2.12B Figure Length per renewl rnch on whole tree sis verged over Gi3 nd Gi6. 11A- Brs re verge of 24 whole tree renewl trees grown in the CRAVO plus or minus stndrd error of the men. 11B- Brs re verge of 16 Whole tree renewl trees grown in the VOEN plus or minus stndrd of the men t Michign Stte University s Clrksville Reserch Center. Lowercse letters seprte mens compring the trining systems, determined using Tukey s LSD, significnce t p length per renewl rnch (m) Figure 2.13A c KGB TSA SSA UFO Gi3 Gi5 Gi6 d 45

57 Figure 2.13 (cont d) Figure 2.13B Figure Length per renewl rnch on whole tree sis verged over KGB, TSA, nd UFO. 12A-Brs re verge of 27 whole tree renewl trees grown in the CRAVO plus or minus stndrd error of the men. 12B- Brs re verge of 18 Whole tree renewl trees grown in the VOEN plus or minus stndrd of the men t Michign Stte University s Clrksville Reserch Center. Lowercse letters seprte mens compring rootstocks, determined using Tukey s LSD, significnce t p numer of syllpetic rnches length per renewl rnch (m) Gi3 Gi5 Gi6 Distl Middle Proximl Figure Numer of sylleptic rnches on ech renewl prent rnch, per permnent structure section of TSA nd UFO on Gi3, Gi5, nd Gi6. Brs re verge of 18 whole tree renewl trees grown in the CRAVO plus or minus stndrd error of the men t Michign Stte University s Clrksville Reserch Center. Lowercse letters seprte mens compring the cnopy sections, determined using Tukey s LSD, significnce t p

58 numer of sylleptic rnches c c c cd cd Distl Middle Proximl Distl Middle Proximl cd cd cd cd Distl Middle Proximl Distl Middle c Proximl c cd cd cd d Distl Middle Proximl Distl Middle Proximl Gi3 Gi5 Gi6 Gi3 Gi5 Gi6 TSA UFO Figure Numer of sylleptic rnches on ech renewl prent rnch, per permnent structure section of TSA nd UFO on Gi3, Gi5, nd Gi6. Three wy interction: trining system y rootstock y permnent structure section. Brs re n verge per section of 12 whole tree renewl trees grown in the VOEN plus or minus stndrd error of the men t Michign Stte University s Clrksville Reserch Center. Lowercse letters seprte mens compring the system y rootstock y section interction, determined using Tukey s LSD, significnce t p numer of sylleptic rnches Distl Middle Gi3 Proximl Distl Figure Numer of sylleptic rnches on ech renewl prent rnch, per permnent structure section of Gi3 nd Gi6 verged over TSA, SSA, nd UFO. Two-wy interction: rootstock y permnent structure section. Brs re n verge per section of 18 whole tree renewl trees grown in the CRAVO plus or minus stndrd error of the men t Michign Stte University s Clrksville Reserch Center. Lowercse letters seprte mens compring the rootstock y section interction, determined using Tukey s LSD, significnce t p Middle Gi6 Proximl 47

59 numer of sylleptic rnches Distl Middle Proximl Distl Middle Proximl Distl Middle Proximl TSA SSA UFO Figure Numer of sylleptic rnches on ech renewl prent rnch, per permnent structure section of TSA, SSA, nd UFO verged over Gi3 nd Gi6. Two-wy interction: trining system y permnent structure section. Brs re n verge per section of 12 whole tree renewl trees grown in the VOEN plus or minus stndrd error of the men t Michign Stte University s Clrksville Reserch Center. Lowercse letters seprte mens compring the twowy interction, determined using Tukey s LSD, significnce t p numer of sylleptic rnches Figure 2.18A KGB TSA SSA UFO 48

60 Figure 2.18 (cont d) 3.5 numer of sylleptic rnches Figure 2.18B KGB TSA SSA UFO Figure Numer of sylleptic rnches on whole tree sis y trining system. Averged over Gi3 nd Gi6. 17A- Brs re nd verge of 24 whole tree renewl trees grown in the CRAVO plus or minus stndrd error of the men. 17B- Brs re nd verge of 16 whole tree renewl trees grown in the VOEN plus or minus stndrd error of the men t Michign Stte University s Clrksville Reserch Center. Lowercse letters seprte mens compring trining systems, determined using Tukey s LSD, significnce t p Figure Trunk cross sectionl re in 2016 of ll loction y trining system y rootstock comintions in the NC-140 sweet cherry rootstock tril t Michign Stte University s Clrksville Reserch Center with Benton s the scion. Brs re n verge of 6 trees for ech KGB, TSA, nd UFO nd 12 trees for SSA on ech rootstock under the CRAVO; under the VOEN, 4 trees for KGB, TSA, nd UFO nd 8 trees for SSA on ech rootstock. 49

61 Numer of sylleptic rnches Length of primry renewl rnch (m) Figure Density sctter plot of length per primry renewl rnch versus numer of sylleptic rnches per renewl rnch of trees tht hve een whole tree renewed. All dt is included, eing comprised of four different trining systems: KGB, TSA, SSA, nd UFO; three different rootstocks: Gi3, Gi5, nd Gi6 t Michign Stte University s Clrksville Reserch Center. Drker hexgon shde indictes higher numer of oservtions. A totl of 1362 primry rnches re plotted. 50

62 Numer of sylleptic rnches Percentile y length of renewl rnch Incresing renewl rnch length Figure Violin plot of distriution of numer of sylleptic rnches per primry renewl rnch of trees tht hve een whole tree renewed. All dt is included, eing comprised of four different trining systems: KGB, TSA, SSA, nd UFO; three different rootstocks: Gi3, Gi5, nd Gi6 t Michign Stte University s Clrksville Reserch Center. Dt is roken up into percentile y renewl rnch length th nd th is the distriution of sylleptic rnches on 340 primry renewl rnches th nd th percentile is the distriution of sylleptic rnches on 341 primry renewl rnches th percentile represents the shortest 25% of rnches, rnch length increses with percentile. 51

63 APPENDIX 52

64 Tle 2.1- Anlysis of vrince (ANOVA) for numer of renewl shoots following whole tree renewl pruning of eight-yer-old Benton sweet cherry trees, grown in the VOEN t MSU Clrksville Reserch Center. SSA dt left out. Type 3 Tests of Fixed Effects Effect Numertor Degrees of Freedom Denomintor Degrees of Freedom F Vlue Pr > F System rootstock system* rootstock Type 3 Tests of Fixed Effects Effect Numertor Degrees of Freedom Denomintor Degrees of Freedom F Vlue Pr > F system Tle 2.2- Anlysis of vrince (ANOVA) for numer of sylleptic rnches following whole tree renewl pruning of eight-yer-old Benton sweet cherry trees, grown in the CRAVO t MSU Clrksville Reserch Center. SSA dt eliminted to compre rootstocks. Type 3 Tests of Fixed Effects Effect Numertor Degrees of Freedom Denomintor Degrees of Freedom F Vlue Pr > F system rootstock system* rootstock Type 3 Tests of Fixed Effects Effect Numertor Degrees of Freedom Denomintor Degrees of Freedom F Vlue Pr > F system

65 Tle 2.3- Anlysis of vrince (ANOVA) for numer of sylleptic rnches following whole tree renewl pruning of eight-yer-old Benton sweet cherry trees, grown in the VOEN t MSU Clrksville Reserch Center. SSA dt eliminted to compre rootstocks. Type 3 Tests of Fixed Effects Effect Numertor Degrees of Freedom Denomintor Degrees of Freedom F Vlue Pr > F system rootstock system* rootstock Type 3 Tests of Fixed Effects Effect Numertor Degrees of Freedom Denomintor Degrees of Freedom F Vlue Pr > F system

66 LITERATURE CITED 55

67 LITERATURE CITED Ayl, M. nd Lng, G.A. (2017). Morphology, cropping physiology, nd cnopy trining, p In: Quero-Grci, J., Iezzoni, A., Pulwsk, J., & Lng, G. A. (Eds.). Cherries: Botny, Production nd Uses. CABI. Atkinson, C., nd Else, M. (2001). Understnding how rootstocks dwrf fruit trees. Compct Fruit Tree, 34(2), Büsgen, M. nd Münch, E. (1929). The Structure nd Life of Forest Trees. John Wiley nd Sons Inc., New York, NY, USA. 436 pp. Burrows, G. E. (2008). Syncrpi nd Tristniopsis (Myrtcee) possess specilised fire-resistnt epicormic structures. Austrlin Journl of Botny, 56(3), Cline, M. G., nd Dong-Il, K. I. M. (2002). A preliminry investigtion of the role of uxin nd cytokinin in sylleptic rnching of three hyrid poplr clones exhiiting contrsting degrees of sylleptic rnching. Annls of Botny, 90(3), Cooper-Ellis, S., Foster, D. R., Crlton, G., nd Lezerg, A. (1999). Forest response to ctstrophic wind: results from n experimentl hurricne. Ecology, 80(8), Eerhrd, S., Finzzi, G., & Wollmn, F. A. (2008). The dynmics of photosynthesis. Annul review of genetics, 42, Fontine, F., Colin, F., Jrret, P., nd Druelle, J. L. (2001). Evolution of the epicormic potentil on 17-yer-old Quercus petre trees: first results. Annls of Forest Science, 58(5), Fontine, F., Kiefer, E., Clément, C., Burrus, M., nd Druelle, J. L. (1999). Ontogeny of the proventitious epicormic uds in Quercus petre. Trees-Structure nd Function, 14(2), Gordon, D., Rosti, A., Dmino, C., nd DeJong, T. M. (2006). Sesonl effects of light exposure, temperture, trunk growth nd plnt crohydrte sttus on the initition nd growth of epicormic shoots in Prunus persic. The Journl of Horticulturl Science nd Biotechnology, 81(3), Lng, G. A. (2000). Precocious, dwrfing, nd productive how will new cherry rootstocks impct the sweet cherry industry? HortTechnology, 10(4), Leyser, O. (2003). Regultion of shoot rnching y uxin. Trends in Plnt Science, 8(11), Ljung, K., Bhlero, R. P., nd Snderg, G. (2001). Sites nd homeosttic control of uxin iosynthesis in Aridopsis during vegettive growth. The Plnt Journl, 28(4),

68 Long, L. E., Lng, G. A., Whiting, M. D., nd Muscchi, S. (2015). Cherry trining systems. Pcific Northwest Extension. Oregon Stte University. University of Idho. Wshington Stte University. Meshm, P. F., Bound, S. A., Grcie, A. J., nd Wilson, S. J. (2009). Incidence nd type of crcking in sweet cherry (Prunus vium L.) re ffected y genotype nd seson. Crop nd Psture Science, 60(10), Nicolini, E., Chnson, B., nd Bonne, F. (2001). Stem growth nd epicormic rnch formtion in understorey eech trees (Fgus sylvtic L.). Annls of Botny, 87(6), O'Hr, K. L., nd Berrill, J. P. (2009). Epicormic sprout development in pruned cost redwood: pruning severity, genotype, nd sprouting chrcteristics. Annls of Forest Science, 66(4), 1-9. O'hr, K. L., nd Vlppil, N. I. (2000). Epicormic sprouting of pruned western lrch. Cndin Journl of Forest Reserch, 30(2), Piene, H., nd Eveleigh, E. S. (1996). Spruce udworm defolition in young lsm fir: the green tree phenomenon. The Cndin Entomologist, 128(06), Perry, R., Lng, G., Andersen, R., Anderson, L., Azrenko, A., Fcteu, T.,... nd Rom, C. (1997, July). Performnce of the NC-140 cherry rootstock trils in North Americ. In III Interntionl Cherry Symposium 468 (pp ). R Core Tem (2017). R: A lnguge nd environment for sttisticl computing. R Foundtion for Sttisticl Computing, Vienn, Austri. URL Schs, T., nd Thimnn, K. V. (1967). The role of uxins nd cytokinins in the relese of uds from dominnce. Americn Journl of Botny, Signorelli, S., Agudelo-Romero, P., Foyer, C. H., & Considine, M. J. (2017). Roles for Light, Energy nd Oxygen in the Fte of Quiescent Axillry Buds. Plnt physiology, pp Soil Survey Stff, Nturl Resources Conservtion Service, United Sttes Deprtment of Agriculture. We Soil Survey. Aville online t the following link: Accessed [Decemer/3/2017]. Spth H Der Johnnistriee. Berlin: Prey. Stone, E. L., nd Stone, M. H. (1943). "Dormnt" versus "Adventitious" uds. Science, 98(2533), Sunderg, B., nd Uggl, C. (1998). Origin nd dynmics of indolecetic cid under polr trnsport in Pinus sylvestris. Physiologi Plntrum, 104(1),

69 Tkemiy, A., Inoue, S., Doi, M., Kinoshit, T., & Shimzki, K. (2005). Phototropins promote plnt growth in response to lue light in low light environments(w). Plnt Cell, 17(4), Tworkoski, T., Miller, S., nd Scorz, R. (2006). Reltionship of pruning nd growth morphology with hormone rtios in shoots of pillr nd stndrd pech trees. Journl of Plnt Growth Regultion, 25(2), Wignll, T. A., Browning, G., nd Mckenzie, K. A. D. (1987). The physiology of epicormic ud emergence in Pedunculte Ok (Quercus rour L.) Responses to prtil notch girdling in thinned nd unthinned stnds. Forestry: An Interntionl Journl of Forest Reserch, 60(1),

70 CHAPTER 3: MAPPING EPICORMIC VEGETATIVE MERISTEMS IN SWEET CHERRY USING X-RAY COMPUTER TOMOGRAPHY Introduction Axillry vegettive meristems (uds) tht remin do not form rnch, remining dormnt, eventully ecome engulfed y rdil growth of the stem; these re considered preventitious epicormic uds, lso termed ltent uds (Büsgen nd Münch, 1929; Stone nd Stone, 1943). Preventitious epicormics uds follow the phyllotxy of the tree; sweet cherry generlly hs spirl phyllotxy with 5 nodes per complete phyllotxic revolution, ~every 72 (Lng et l., 2004), or more ccurtely, 5 nodes per two revolutions, every 144 (G.A. Lng, personl communcition). Adventitious epicormic uds form independently, typiclly fter wounding event (Fink, 1983, 1999; Kuppi et l., 1987). Epicormic uds constitute the epicormic potentil of woody plnt to develop epicormic rnches nd therefore re importnt for orchrdists studying pruning nd forest mngers evluting timer qulity due to knots produced y epicormic rnches or forest regenertion following fire or insect defolition. Preventitious epicormic uds mintin vsculr connection with the pith of the prent rnch from which they formed, n epicormic trce (Fontine et l., 1998). An epicormic trce consists of densely pcked prenchym cells, mesuring 2-5 mm thick. Cells in the trce ecome more lignified towrds the pith (Burrows, 2000). Epicormic trces occur perpendiculr to the pith (Büsgen nd Münch, 1929). Burrows (2000) found simple epicormic trces, more commonly found on smll stems, mesured 2.0 mm high; complex trces mesured 3-5 mm high nd consisted of two smller strnds. Trces elongte with nnul growth, mintining the epicormic ud s persistence eneth the rk (Stone nd Stone, 1943). 59

71 Preventitious epicormic uds cn e seprted into lrge nd smll uds. Buds tht mesure less thn 2 mm long re considered smll, nd re usully found t the se of shoot. Lrge preventitious epicormic uds, locted long the shoot (Fontine et l., 1998), re 3-4 mm long, nd re more developmentlly complex thn smll preventitious epicormic uds. Meristemtic res 100 µm long nd 30 µm wide re present in the upper third of lrge preventitious epicormic uds. Secondry ud primordi chrcterize the lower two thirds (fig. 3.1A). Smll uds re composed of only terminl meristem surrounded y scles, nd do not hve secondry ud primordi (Fontine et l., 1998) (fig. 3.1B). Lrge preventitious epicormic uds tht do not sprout re more likely to scise thn smll epicormic uds (Hrmer, 1991; Fontine et l., 2001); smll uds persist longer thn lrge uds (Gruer, 1994). Lrge uds re more likely to elongte into new shoots thn re smll uds (Brhm nd Kellison, 1987). Colin et l. (2010) trcked epicormic trces in sessile ok (Quercus petre) trunks using X-ry computer tomogrphy (CT). Both simple epicormic uds nd ud clusters were found in the scnned sections. Epicormic rnches developed horizontlly in the trunk, while sequentil rnches rose t n olique ngle to the pith (Colin et l., 2010). This preliminry study imed, first nd foremost, to determine if epicormic trces (nd therefore epicormic uds) in sweet cherry cn e visulized using x-ry computer tomogrphy. Likewise, cn x-ry computer tomogrphy distinguish etween simple nd complex epicormic trces nd e used to exmine the development of epicormic rnches. Mpping epicormic uds hs the potentil to improve whole tree renewl y determining where epicormic rnches re most likely to rise. 60

72 Mterils nd Methods Plnt Mteril A 1.14 m long section of 8-yer-old trunk of NY 119 on Gisel 12 sweet cherry tht hd een sujected to whole tree renewl ws used for the scn. Eight sequentil rnches of the tree hd een removed t loom 2016, nd the trunk section for scnning ws collected in August 2016 fter the top of the tree hs een removed t 1.5 m from the ground. The CT scn ws done in Decemer 2016 fter drying the trunk section. The trunk circumference mesured 32.5 cm t the se, 27.6 cm t the middle, nd 24.7 cm t the top of the section. X-Ry Computer Tomogrphy Scn X-ry scnning ws performed t Michign Stte University s Deprtment of Rdiology (Est Lnsing, MI) using whole ody mgnetic resonnce scnner (GE Sign HDX 3.0T, Chicgo, Il). The CT scn ws done in Decemer 2016 fter drying the trunk section. The high density of prenchym cells within the epicormic trce mens tht this trce shows up righter the rest of the trunk. Contrsts in the scn is influenced y moisture content of the trunk, with strkness eing greter in ir-dried thn fresh wood (Freyurger et l., 2009). Greter contrsts llow for epicormic trces to e more esily distinguished from the rest of the trunk. Scnning imge slice thickness ws set t ~0.625 mm per slice, the entire scn took out minute. 3-Dimensionl Reconstruction The 3-D trunk imge ws reconstructed using 3D Slicer softwre version 4.8 (open source, Cmridge, MA; Federov et l., 2012). The pint rush in segment editor ws used to first lel the end of ech epicormic trce s either complex or simple trce. Complex epicormic trces were those tht hd more thn one conjoining epicormic trce (fig. 3.1A). Simple epicormic trces were those with only single trce (fig. 3.1B). 61

73 Complex or simple epicormic trces were mrked with lrge or smll sphere, respectively. A second segment ws then creted using the threshold tool in segment editor tht selected the entire trunk. Results 1,830 imges were produced from the scn. Epicormic trces were visile throughout the trunk section; these trces showed up righter thn the surrounding trunk. There were 104 totl epicormic trces; 22 were complex trces (fig. 3.2A) nd 82 were simple (fig. 3.2B), wht ppered to e two conjoining trces. These trces were spred eqully throughout the trunk nd pper to follow the phyllotxy of the tree. Mny of the complex trces were flnked with simple epicormic trce on either side; these three trces originte t the pith: the simple trces were oriented outwrd t n ngle forming V, with the complex trce splitting the middle (fig. 3.2C). These V-shped trces occurred t sites with urls on the trunk. Between whole tree renewl pruning t loom nd collection of the trunk section in August, six epicormic rnches hd developed in the scnned section of trunk during the spring nd summer. Four of these epicormic rnches (1 nd 2, 4 nd 5) occurred t the sme spot (fig. 3.3A nd 3.3C. In cross section, five of the six epicormic rnches (epicormic rnches 1-5) hd cler epicormic trces ck to the centrl pith, which hd left the nnul growth rings undistured (figs. 3.3A-C). However, the loction of epicormic rnch 6 showed rek in the nnul growth ring nd no cler epicormic trce to the centrl pith in cross section (fig. 3.3D). Epicormic rnches 1-5 were from complex epicormic trces, while epicormics rnch 6 ppers to e from either simple epicormic trce t the se of sequentil shoot or n dventitious epicormic ud. Epicormic rnches 1 nd 2; 4 nd 5 were seprte rnches rising from the sme position (fig 3.3A nd 3.3C). 62

74 Discussion Epicormic trces re densely pcked prenchym cells (Fontine et l., 1998); since higher density regions of CT scns show up righter (Freyurger et l., 2009), epicormic trces re esily visulized using CT scnning. Trces were locted eqully throughout the trunk, nd there were only few instnces where the trce did not extend to the outside, suggesting tht environmentl fctors did not ffect persistence of preventitious epicormic uds during the eightyer life of this tree. It must e noted tht this section constitutes the ottom hlf of the tree trunk, so it is possile tht the concentrtion of epicormic uds my hve differed in the upper hlf of the trunk, if initil growth rte or incresed light exposure over time might influence epicormic ud density or persistence. Burl wood is n outgrowth of the trunk, typiclly cused y insect dmge, fungi or nother stress tht cretes distortion in the wood grin. A V-shped trce two simple trces flnking complex trce - ws present t urls in cross-section; the nnul growth rings pper wvy round these trces (fig. 3.2C). Such V trce ws reported in scn done on sessile ok (Colin et l., 2010). In our study, four of the six epicormic rnches (1, 2, 4, nd 5) produced on the scnned trunk section following whole tree renewl rose from V trces (figs. 3.3A nd 3.3C). Ech of these loctions produced two epicormic rnches; epicormic uds present in urls my, therefore, e n importnt source of epicormic rnches in sweet cherry. Epicormic rnches 1-5 hd connection ck to the centrl pith nd developed outside of the nnul growth ring (fig. 3.3A-C). Epicormic rnch 6 ws n nomly in this regrd. The cross section t this epicormic rnch showed rek through ll of the growth rings (fig. 3.3D), in the sme wy tht sequentil rnch develops (fig. 3.2D). A possile explntion for this is tht the epicormic rnch developed t the se of sequentil rnch. However, there is no 63

75 sequentil rnch visile on the outside of the trunk, ut there re few signs tht the sequentil rnch could hve ecome engulfed y the epicormic rnch (fig. 3.3D). There ppers to e two knots in cross section tht this epicormic rnch hs engulfed (fig. 3.3D), the one on the right is n epicormic knot () developing t the se of the originl sequentil rnch, while () hs nnul growth rings nd is therefore sequentil knot. Secondly, there is rection wood on the underside of the epicormic rnch, which is evidence of sequentil rnch (fig. 3.4). Future Directions These results indicte tht preventitious epicormic uds cn e mpped throughout mture section of tree trunk. While preventitious epicormic uds don t constitute the entire epicormic potentil of tree, mpping llows estimtion of the rtio of dventitious to preventitious meristems in epicormic rnch initition nd consequently the degree to which epicormic rnch potentil cn e quntified. In the context of whole tree renewl, this hs the potentil to provide new insights into how removl of ctive vegettive meristems ffects the potentil sources of epicormic rnching. Future studies my e vlule to test whether culturl tretments, such s plnt growth regultors or synthetic hormones, could directly ctivte epicormic uds to initite renewl shoots t specific sites long the trunk. Preventitious epicormic uds rise in predictle pttern, following the phyllotxy of the tree. Sweet cherry hs 2/5 phyllotxy, mening tht node will rise directly ove nother one fter two spirls of five successive nodes round the rnch. Mpping preventitious epicormic uds cn provide dt on how growth ffects the distnce nd ngle etween preventitious epicormic uds; llowing for model to e developed tht cn predict where preventitious epicormic uds persist. Ultimtely this model could e pplied to field setting, 64

76 where grower could utilize sequentil rnch s lndmrk to se where preventitious epicormic ud persists. 65

77 Figure 3.1A Figure 3.1B Figure 3.1- Scnning Electronic microscope imges of lrge preventitious epicormic ud (1A) with secondry ud primordi surrounding the ud in the center; smll preventitious epicormic uds (1B) without secondry ud primordi (Fontine et l., 1999). 66

78 Figure 3.2A Figure 3.2B Figure 3.2C Figure 3.2D Figure 3.2- Imges in cross-section from X-ry CT scn of 8-yer-old section of sweet cherry of the vriety NY 119 grfted onto Gisel 12 rootstock trunk: 2A) complex epicormic trce, 2B) simple epicormic trce, 2C) V trce with centrl complex trce, flnked y simple trce on either side, 2D) sequentil rnch. 67

79 Figure 3.3A Figure 3.3B Figure 3.3C Figure 3.3D Figure Epicormic rnches in cross-section: 3A) epicormic rnch 1 nd 2; 3B) epicormic rnch 3; 3C) epicormic rnch 4 nd 5; 3D) epicormic rnch 6. 68

80 Figure 3.4- Epicormic rnch numer 6 with rection wood on the underside of the rnch. 69