Vigor control in McIntosh apple trees by growth inhibitors

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1 Vigor control in McIntosh pple trees y growth inhiitors L. Rufto 1, A.F. Brighenti 1, A.D. Rufto 2, L.I. Dominguez 3 nd T.L. Roinson 3 1Snt Ctrin Stte University (UDESC), College of Agric. nd Life Science, Lges, SC, Brzil; 2 Brzilin Agriculturl Reserch Corportion (EMBRAPA), Vcri, RS, Brzil; 3 Dept. of Horticulture, NYSAES, Cornell University, Genev, NY, USA. Astrct We evluted the effects of two gierellin iosynthesis inhiitors [Prohexdione-C (Apogee 25 ppm) nd Trinexpc-ethyl (Moddus 225 ppm)], on shoot growth of mture McIntosh /M.9 pple trees. The growth regultors were pplied 7 dys fter loom, when shoots were 5 cm long. Shoot length ws mesured every 15 dys to determine growth rte. Shoots were mesured in the lower, middle nd upper portion of tree nd ccording type (terminl nd lterl shoots). The numer of fruits tree -1, yield nd yield efficiency were determined t hrvest. After hrvest, fruits were clssified ccording to the color. Both growth inhiitors reduced shoot growth rte pproximtely 3% nd reduced the dily growth rte (cm dy -1 ) of ll types of shoots nd in ll positions of tree. Dily growth rte ws ffected y shoot position. Growth rte of shoots locted in lower portion of tree ws reduced more thn for shoots in the upper prt of the tree. Likewise, terminl shoot growth rte ws reduced less thn lterl shoot growth rte. Trinexpc-ethyl (Moddus 225 ppm) incresed the numer of fruits tree -1 nd yield efficiency ut reduced return loom out 57% compred to the untreted control nd 65% when compred to Apogee. Both growth inhiitors hd positive effect on fruit color, which ws proly due to improved light penetrtion into the cnopy. Keywords: Mlus domestic Borkh., Prohexdione-C, Apogee, Trinexpc-ethyl, Moddus, shoot growth rte INTRODUCTION Excessive vegettive growth in fruit trees is mjor concern for the producer ecuse it competes with fruit growth (Byers nd Yoder, 1999; Bsk nd Rdemcher, 2; Cost et l., 22). This competition is t its strongest during the first 5 dys fter full loom when shoot nd fruit growth is mximl (Byers nd Yoder, 1999; Elfving et l., 22; Smit et l., 25). Excessive shoot growth lso hs negtive effect on fruit qulity, yield nd pest control (Greene, 1999; Miller nd Tworkoski, 23). In ddition, shding cused y excessive shoot growth hs negtive effect on flower ud induction nd the qulity of the return loom (Greene, 1999; Miller nd Tworkoski, 23). Among the methods to reduce shoot growth is the use of growth regultors sed on gierellins iosynthesis inhiitors (Smit et l., 25). Trinexpc-ethyl nd prohexdioneclcium re growth retrdnts of the cylcyclohexnedione-type. They lock certin dioxygenses ctlyzing the lte steps of gierellin metolism y eing structurl mimics of 2-oxoglutrte, which is the co-sustrte of these enzymes (Rdemcher, 2). Trinexpc-ethyl hs een developed primrily s n nti-lodging gent for smll grins nd for use s turf growth regultor. Prohexdione-clcium is eing commercilized s n nti-lodging gent for rice, cerels, nd turf grsses grown for seed production. It is lso used to control vegettive growth in fruit trees nd ground nuts (Rdemcher nd Bucci, 22). The ojective of this study ws to evlute the effects of two gierellin iosynthesis inhiitors on vegettive growth nd fruiting of mture McIntosh pple trees. Act Hortic ISHS 217. DOI /ActHortic Proc. Int. Symp. on Physiologicl Principles nd Their Appliction to Fruit Production Ed.: T. Roinson 223

2 MATERIALS AND METHODS At Cornell s New York Stte Agriculturl Experiment Sttion - NYSAES ( N; W, 221 m.s.l.), uniform 17-yer-old McIntosh /M.9 trined to verticl xis system were used for this experiment. The three tretments were: (1) untreted control; (2) Prohexdione-C (Apogee 25 ppm); (3) Trinexpc-ethyl (Moddus 225 ppm). Sprys were pplied on My 31, 213, 7 dys fter loom, when shoots were 5 cm. Tretments were orgnized in rndomized complete lock design, with 3 plots nd 1 replictions. Full loom on McIntosh trees occurred on My 24, 213. Whole trees were spryed with n irlst Lipco tunnel spryer. The djuvnt Silwet L- 77 ws used for ll tretments. Two gurd trees were included etween experimentl units to minimize cross-contmintion of tretments through spry drift during ppliction. Spry pplictions were conducted during fvorle wether conditions where rinfll did not occur for the following 24 h. Ten representtive new extension shoots per tree were rndomly tgged ccording to the position (lower, middle nd upper portion of tree) nd type (terminl nd lterl shoots). Their length ws mesured t the time of the first ppliction nd then t 2 weeks intervls until the cesstion of shoot growth. Trunk cross-sectionl re (TCSA) ws clculted from trunk circumference, mesured t 3 cm ove the soil line in the fll. At hrvest, the numer nd weight of fruit hrvested per tree (kg) ws recorded nd yield efficiency (kg fruit cm -2 TCSA) ws clculted. After hrvest, fruits were clssified ccording percentge of the skin surfce with red color into 5 ctegories: Utility (-2% red color). No.1 (2-35%, Fncy (4-5%, X Fncy (5-75% nd XX Fncy (75-1%. Dt were nlyzed y nlysis of vrince nd where significnt differences were detected, mens were seprted y Duncn s multiple rnge test (P=.5). RESULTS AND DISCUSSION The inhiiting effect of oth ioregultors on shoot growth ws clerly evident 2 week following the ppliction of the chemicls (Figure 1). In the lower portion of the tree Apogee 25 ppm cused significnt reduction in shoot growth rte compred to the control, while Moddus 225 ppm hd n intermedite effect which did not differ from the control trees or the Apogee trees (Figure 1A). In the middle nd upper portions of tree nd Apogee 25 ppm nd Moddus 225 ppm significntly reduced the growth rte compred to the control (Figures 1B, C). With terminl shoots, Apogee 25 ppm cused the gretest reduction in shoot growth rte, while Moddus 225 ppm resulted in n intermedite effect ut not different from the control trees or the Apogee trees (Figure 1D). With lterl shoots Apogee 25 ppm nd Moddus 225 ppm significntly reduced the growth rte compred to the control (Figure 1E). Both ioregultors reduced finl shoot length in ll types nd positions of shoots (Tle 1). The gretest reduction occurred in the middle portion of tree with men shoot lengths pproximtely 4% tht of the control (Figure 1B). Both ioregultors pplied in the lower nd upper portions of tree reduced shoot length from 25 to 3% (Figures 1A, C). Lterl shoot growth rte ws reduced 35% compred to the controls (Figure 1E), while terminl shoot growth rte ws reduced y 3 nd 15% y Apogee 25 ppm nd Moddus 225 ppm, respectively (Figure 1D). Others (Byers nd Yoder, 1999; Unrth, 1999; Miller, 22) hve found greter shoot growth inhiition when Prohexdione-C ws pplied t full loom. Mxson nd Jones (22) oserved tht Trinexpc-ethyl reduced pple tree shoot growth eginning 1 to 14 dys fter ppliction nd the inhiition continuing for nother 3 dys. 224

3 Growth Rte (%) A Growth Rte (%) B Dys After Full Bloom Untreted Control Moddus 225 ppm Apogee 25 ppm Dys After Full Bloom Untreted Control Moddus 225 ppm Apogee 25 ppm Growth Rte (%) C Growth Rte (%) D Dys After Full Bloom Untreted Control Moddus 225 ppm Apogee 25 ppm Dys After Full Bloom Untreted Control Moddus 225 ppm Apogee 25 ppm Growth Rte (%) E Dys After Full Bloom Untreted Control Moddus 225 ppm Apogee 25 ppm Figure 1. Shoot growth rte of lower shoots (A), middle shoots (B), upper shoots (C), terminl shoots (D) nd lterl shoots (E) of McIntosh pple trees t Genev, NY in 213. Tle 1. Growth inhiitors effect on shoot growth nd productive spects of McIntosh pple trees t Genev, NY in 213. Tretment Shoot growth Yield Fruit size Yield efficiency # fruits tree (cm) (kg tree -1 ) (g) (kg cm -2 ) Untreted control Moddus 255 ppm Apogee 25 ppm LSD P Significnce 1 * * NS * * 1 NS, or * indicte the effect of tretment ws either non significnt or significnt t P.5 level. Plnts treted with Moddus 225 ppm produced significntly more fruits tree -1 thn the untreted control, ut did not differ significntly from trees treted with Apogee 25 ppm (Tle 1). Despite higher fruit numers, yield ws not ffected y the ppliction of ioregultors due to smller fruit size on trees treted with the ioregultores. The reduction in fruit size due to ppliction of Moddus nd Apogee ws proly direct effect of higher fruit set. Greene (1999) nd Sugr et l. (22) hd similr results where 225

4 growth inhiitor tretments resulted in smller verge fruit size of pers nd pple cultivrs. Yield efficiency ws significntly higher in plnts treted with Moddus 225 ppm. An incresed fruit set is n indiction tht reduced shoot growth erly in the seson results in incresed vilility of ssimiltes to support the erly growth of more fruits, however, the greter numer of fruits results in reduced crohydrte supply to ech fruit nd greter competition for ssimiltes lter in the seson with the net result of smller fruit. This could potentilly e mnged y more ggressive chemicl thinning or with erlier hnd thinning (Smit et l., 25). Plnts treted with Moddus 225 ppm produced more fruits clssified s X Fncy, while plnts treted with Apogee 25 ppm produced higher percentge of fruits clssified s XX Fncy ctegory. The untreted control produced higher percentge of poorly colored fruits clssified s Utility (Tle 2). Tle 2. Growth inhiitors effect on fruit qulity of McIntosh pple trees t Genev, NY in 213. Tretment Utility (-2% N.1 (2-35% Fruit red color (%) Fncy (4-5% X Fncy (5-75% XX Fncy (75-1% Untreted control Moddus 255 ppm Apogee 25 ppm LSD P Significnce 1 * NS NS * * 1 NS, or * indicte the effect of tretment ws either non significnt or significnt t P.5 level. The percentge of highly colored fruits ws higher in plnts treted with Moddus nd Apogee ecuse they reduced shoot growth rte nd incresed sunlight inside the cnopy. Red pigment development in pples requires reltively high light levels within the cnopy, nd in shded prt of the McIntosh pple fruits remins green. High fruit qulity comes from comining good light distriution in the cnopy nd high light interception (Roinson et l., 1991). The spry of Moddus significntly reduced return loom out 43% compred to the untreted control while Apogee reduced return loom y 12%, which ws not significntly different thn the control (Tle 3). Both gierellin inhiitors ct on GA2 inhiition, ut Moddus proly promotes the liertion of GA2 fter its effect wers off. Since it is shorter lived thn Apogee this likely results in worse return loom the next seson thn with Apogee. Tle 3. Growth inhiitors effect on percentge of return loom of McIntosh pple trees t Genev, NY in 213. Tretment Return loom (%) Lower Medium Upper Totl tree Untreted control Moddus 255 ppm Apogee 25 ppm LSD P Significnce 1 * * * ** 1 ** or * indicte the effect of tretment ws significnt t P.5 or P.5 levels. CONCLUSIONS Both growth inhiitors reduced shoot growth rte pproximtely 3% nd reduced the dily growth rte of ll types of shoots nd in ll positions of tree. 226

5 Shoot position ffected dily growth rte. Growth rte of shoots locted in the lower portion of tree ws reduced more thn for shoots in the upper prt of the tree. Likewise, terminl shoot growth rte ws reduced less thn lterl shoot growth rte. Both growth inhiitors hd lso incresed the numer of fruits tree -1, which resulted in smller fruit size ut hd positive effect on fruit color, which ws proly due to improved light penetrtion into the cnopy. Trinexpc-ethyl (Moddus 225 ppm) reduced return loom considerly which mkes it less desirle growth inhiitor thn Apogee for pple. Literture cited Bsk, A., nd Rdemcher, W. (2). Growth regultion of pome nd stone fruit trees y use of prohexdione- C. Act Hortic. 514, Byers, R.E., nd Yoder, K.S. (1999). Prohexdione-clcium inhiits pple, ut not pech tree growth, ut hs little influence on pple fruit thinning or qulity. HortScience 34, Cost, G., Andreotti, C., Stini, E., Bregoli, A.M., Bucchi, F., Spd, G., nd Mzzini, F. (22). The effect of prohexdione-c on vegettive nd cropping performnce nd fire light control of per trees. Act Hortic. 596, Elfving, D.C., Sugr, D., nd Fuion, D. (22). Per tree shoot growth ptterns in reltion to chemicl control of vegettive growth with prohexdione-c (Apogee). Act Hortic. 596, ActHortic Greene, D.W. (1999). Tree growth mngement nd fruit qulity of pple trees treted with prohexdioneclcium (BAS 125). HortScience 34, Mxson, K.L., nd Jones, A.L. (22). Mngement of fire light with gierellin inhiitors nd sr inducers. Act Hortic. 59, Miller, S.S. (22). Prohexdione clcium control vegettive shoot growth in pple. J. Tree Fruit Prod. 3 (1), Miller, S.S., nd Tworkoski, T. (23). Regulting vegettive growth in deciduous fruit trees. PGRSA Q. 31, Rdemcher, W. (2). Growth retrdnts: effects on gierellin iosynthesis nd other metolic pthwys. Annu. Rev. Plnt Physiol. Plnt Mol. Biol. 51 (1), PuMed Rdemcher, W., nd Bucci, T. (22). New plnt growth regultors: high risk investment? Horttechnology 12, Roinson, T.L., Lkso, A.N., nd Crpenter, S.G. (1991). Cnopy development, yield, nd fruit qulity of Empire nd Delicious pple trees grown in four orchrd production systems for ten yers. J. Am. Soc. Hortic. Sci. 116, Smit, M., Meintjes, J.J., Jcos, G., Stssen, P.J.C., nd Theron, K.I. (25). Shoot growth control of per trees (Pyrus communis L.) with prohexdione-clcium. Sci. Hortic. (Amsterdm) 16 (4), j.scient Sugr, D., Elfving, D.C., nd Mielke, E.A. (22). Effects of prohexdione-c (ApogeeTM) on lossoming, production nd fruit qulity in per. Act Hortic. 596, Unrth, C.R. (1999). Prohexdione C: promising chemicl for controlling vegettive growth of pples. HortScience 34,

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