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1 Biologil Control 56 (2) 5 24 Contents lists ville t SieneDiret Biologil Control journl homepge: Compost mendments enhne pet suppressiveness to Pythium ultimum, Rhizotoni solni nd Slerotini minor Ctello Pne,, Rirdo Spini, Alessndro Piolo, Felie Sl, Giulino Bonnomi Foltà di Agrri, Diprtimento di Arorioltur, Botni e Ptologi Vegetle (Ar.Bo.P.Ve), Università di Npoli Federio II, vi Università n., 855 Portii (NA), Itly Foltà di Agrri, Diprtimento di Sienze del Suolo, dell Pint, dell Amiente e delle Produzioni Animli (DiSSPAPA), Università di Npoli Federio II, vi Università n., 855 Portii (NA), Itly Consiglio per l Rier e l Sperimentzione in Agrioltur Centro di Rierhe per l Ortioltur, Aziend Sperimentle di Bttipgli, S.S. 8 n.24, 849 Bttipgli (SA), Itly rtile info strt Artile history: Reeived 7 Deemer 29 Aepted Otoer 2 Aville online 8 Otoer 2 Keywords: Compost Pet 3 C-CPMAS-NMR Disese suppression Pythium ultimum Rhizotoni solni Slerotini minor Pet is the most ommon orgni mteril used for the preprtion of potting mix euse of its homogeneous nd fvorle gronomi hrteristis. However, this orgni mteril is poorly suppressive ginst soilorne pthogens nd fungiides re routinely used to mnge dmping-off diseses. In the present study, we investigted the suppressive pility of five ompost pet mixtures towrds the plnt pthogens Pythium ultimum, Rhizotoni solni nd Slerotini minor Lepidium stivum pthosystems. For ll orgni medi, 8 prmeters were mesured inluding enzymti tivities (glunse, N-etylgluosminidse, hitoiosidse nd hydrolysis of fluoresein diette), miroiologil (BIOLOG Ò Eo- Pltes, ulturle teri nd fungi), nd hemil fetures (ph, EC, totl, extrtle nd humi ron, totl nd orgni N, NH 4 N, totl protein nd wter ontent). In ddition, 3 C-CPMAS-NMR spetrosopy ws used to hrterize the orgni mterils. Pet mended with omposts redued disese dmpingoff used y P. ultimum, R. solni nd S. minor in 6% of the mixtures nd ompost derived from niml mnure showed the lrgest nd most onsistent disese suppression. Steriliztion deresed or eliminted suppressiveness of 42.8% of the mixtures. The most useful prmeters to predit disese suppression were different for eh pthogen: extrtle ron, O-ryl C nd C/N rtio for P. ultimum, lkyl/o-lkyl rtio, N-etyl-gluosminidse nd hitoiosidse enzymti tivities for R. solni nd EC for S. minor. Our results demonstrte tht the ddition of omposts to pet ould e useful for the ontrol of soilorne pthogens. Ó 2 Elsevier In. All rights reserved.. Introdution Plnts produed in ontiner-medi re suseptile to soilorne pthogens using dmping-off diseses, whih use lrge yield loss in nursery nd soil-less systems. Inresing puli onerns regrding food sfety nd environmentl pollution fored the progressive restritions of soil fumignts nd fungiides, nd enourged the reserh of lterntive methods for the ontrol of suh fungl diseses (Lzrovits, 2). Exploittion of the disese suppressive properties of orgni mendments hs een proposed to integrte or reple trditionl ontrol strtegies (Nole nd Coventry, 25). Pet is the most utilized orgni sustrte for the preprtion of potting mix (Crlile, 29) euse of its positive gronomi hrteristis suh s onstnt hemil nd physil properties, high wter retention pity, optiml porosity nd ontrolled ph. However, pet is hrdly ever suppressive ginst soilorne Corresponding uthor. Fx: E-mil ddress: tello.pne@enter.it (C. Pne). pthogens suh s Rhizotoni solni (Kühn) nd Pythium spp. (Bonnomi et l., 27), nd fungiides re routinely used to mnge dmping-off diseses. Moreover, the use of pet for hortiulturl purpose will proly e disourged euse of its limited sustinility nd negtive impt on glol limti hnges due to the prodution of greenhouse gses (Crlile, 29). Therefore, the sustitution of pet with other orgni sustrtes is urgently needed. In this view, the use of omposts ppers to e promising strtegy s demonstrted y suessful pplitions in United Sttes nd Netherlnds (Veeken et l., 25). Compost is otined y the iologil deomposition of orgni mterils whih determines their hemil stiliztion nd the snitiztion from humn nd plnt pthogens nd weed seeds (Nole nd Roerts, 24). Composts mendment hs een proposed to ontrol diseses used y soilorne diseses, nd there re mny exmples of pthogens effetively ontrolled y the pplition of suh orgni mendments: Mrophomin phseolin (Tssi) (Lodh et l., 22), R. solni (Termorshuizen et l., 27) nd Vertiillium dhlie (Kle.) (Mlndrki et l., 28), severl speies of Fusrium (Borrero et l., 24), Pythium (Sheuerell /$ - see front mtter Ó 2 Elsevier In. All rights reserved. doi:.6/j.ioontrol.2..2

2 6 C. Pne et l. / Biologil Control 56 (2) 5 24 et l., 25) nd Slerotium (Coventry et l., 25). However, fr less ttention hs een pid to the effet of orgni mendments on some importnt pthogens suh s Slerotini spp. (Lumsden et l., 983). The pility of omposts to suppress plnt diseses ould e relted to: enhned tivities of ntgonisti miroes tht, ompeting with pthogens for sustrte resoures, use miroiostsis (Serr-Whittling et l., 996); relese of fungitoxi ompounds during deomposition (Kuter et l., 988); nd the indution of systemi resistne in host plnts (Zhng et l., 996). The omined pplition of pet nd suppressive omposts t reltively low dosges, rnging from % to 2% y volume, ppers to e promising perspetive euse it mintins the gronomi fetures of pet ut, simultneously, enhnes the suppressive pility of the potting mixtures (Veeken et l., 25; vn der Gg et l., 27). However, inonsistent disese suppression hs een often reported, nd the diffiulty in prediting ompost suppressiveness seriously hindered their prtil use (Bonnomi et l., 2). Sine growers require onsistent effet of omposts, the possiility of prediting suppressiveness to pthogens is entrl issue for reserhers. Aim of this study is to ssess the pility of five omposts to enhne the suppressiveness of pet-ompost potting mixtures to three ommon soilorne pthogens: Pythium ultimum (Trow), R. solni nd Slerotini minor (Jgger). To identify the mehnisms tht determine ompost disese suppressiveness, the orgni mterils were hemilly nd iologilly hrterized y mesuring 8 prmeters inluding hemil, miroiologil, nd enzymti ones. 2. Methods 2.. Orgni medi Two ommeril pet potting mixes were used. Smple identified s P whih onsisted of 5% light nd 5% drk Sphgnum pets nd.5 kg/m 3 PG-Mix (N, P, K); nd P2, omposed of 7% light nd 3% drk Sphgnum pets nd.5 kg/m 3 PG-Mix (N, P, K). Five omposts derived from different feedstok origin were olleted t ommeril Itlin ftories. The following mterils were olleted: () omposted residues otined from vitiulture nd enologil ftory (herefter C); omposted orgni frtion of differentited muniipl io-wste (C2); omposted orgni frtion of undifferentited muniipl io-wste (C3); omposted ow mnure (C4) nd, finlly, medium otined from omposting mixture of 5% orgni frtion of differentited muniipl iowste nd 5% pet (C5). Smples were olleted y su-smpling liquots for eh ommeril produt (stoks size rnged etween nd 5 kg) Dmping-off disese iossy The suppressive pility of P mended with the five different omposts nd P2 not mended to P. ultimum, R. solni nd S. minor dmping-off ws evluted y pot ssys using Lepidium stivum L. s host plnt. P pet ws mended with the five omposts t two rtes (% nd 2% v/v). Biossys were rried out with L. stivum whih is reognized s sensitive nd relile plnt test (Bonnomi et l., 26; Erhrt et l., 999). Not mended P nd P2 were used s ontrols euse they re two ommon hortiulturl medi. All iossys were rried out with sterile (twie utolved) nd not sterile medium. Severl pthogen isoltes were otined from disesed lettue (Ltu stiv L.) (S. minor), roket (Eru stiv L.) (P. ultimum), nd ge (Brssi olere L.) (R. solni) nd mintined on PDA medium. Isoltes of eh speies were preliminrily tested for pthogeniity on lettue, L. stivum, nd showed very similr ehvior. Therefore, one isolte for eh speies ws used in the iossys. Isoltes were stored on the fungi olletion of the Deprtment of Aroriulture, Botny nd Plnt Pthology, University of Nples Federio II, Itly. Pthogen inoul were prepred s follows: ommon millet seeds were pled in.5 l flsks, sturted with PDB (potto dextrose roth) solution (/ w/w) nd twie utolved. Flsks were inoulted with fungi ultured on PDA (potto dextrose gr) for 7 dys, nd inuted for 2 dys t 2 C. The resulting fungl millet inoulum ws ir-dried for 3 dys, powdered in mortr, nd dded t four levels to the potting mixtures. Pthogen inoulum ws used t different onentrtions (%,.3%, % nd 3% w/w, dry weight) to test the effet of different inoulum density nd to void the flttening effet of the results often oserved when only one onentrtion is used (Termorshuizen et l., 27). In the ontrols, non-inoulted ommon millet prepred s desried ove ws dded. Pots (7 m dimeter nd ml volume pity) were filled with the different orgni mixtures nd sown with 2 L. stivum seeds v. Comune (Blumen), moistened to field pity nd rrnged in greenhouse (25 C) following omplete rndomized design. Pot distriution ws rerrnged rndomly every 2 dys to void the effets of environmentl heterogeneity in the greenhouse. After 7 dys disese inidene ws reorded s perentge of disesed plnts. Dmping-off perentge ws lulted s desried y Veeken et l. (25): %DO ¼ HPo HPi ð%þ HPo where HPo is the numer of helthy plnts in the non-inoulted ontrol mixture nd HPi is the numer of helthy plnts in the inoulted potting mixes. Glolly, the experimentl design inluded seven orgni mixtures pplied t two rtes, oth sterile nd not sterile with four inoulum levels nd five replitions. The full experimentl design ws pplied on the three pthogens for totl of 68 pots nd 33,6 sowed seeds. The experiment hs een repeted twie Chemil nlyses nd 3 C-CPMAS-NMR spetrosopy Different nitrogen forms (totl N, totl orgni N = TON, nd NH 4 N) were determined ording to the Europen diretive (Reglement CE n.23 of 3//23), nd different ron forms (totl orgni ron = TOC, totl extrtle ron = TEC, nd humi ron = C H ) were determined ording to the Itlin diretive (G.U. n.2 del 26//2). Wter ontent of orgni medi ws determined fter desition t 5 C for 72 h. EC nd ph were determined ording to the offiil methods of the Itlin Ntionl Soiety of Soil Siene (Violnte, 2). All pets nd omposts were hrterized y 3 C Cross Polriztion Mgi Angle Spinning (CPMAS), Nuler Mgneti Resonne (NMR) spetrosopy tht llow detiled hrteriztion of the hemil omposition of omplex orgni mtter (Boehm et l., 997; Kögel-Knner, 22). 3 C NMR spetr were otined in the solid stte (CPMAS) under the sme onditions in order to llow quntittive omprison mong spetr. Experiments were rried out with Bruker AVANCE 3, equipped with 4 mm Wide Bore MAS proe, operting t 3 C resonting frequeny of MHz. Smples ( 5 mg) were pked in 4 mm zironi rotors with Kel-F ps nd spun t 3 ± khz. To ount for possile inhomogeneity of the Hrtmnn Hhn ondition t high rotor spin rtes, H rmp sequene ws pplied in CP experiments during ontt time (CT) of ms. The 3 C-CPMAS experiments were onduted olleting 6 sns with 2266 dt

3 C. Pne et l. / Biologil Control 56 (2) points over n quisition time of 25 ms, nd reyle dely of 2. s. The Bruker Topspin.3 softwre ws used to ollet nd elorte the spetr. All the free indution deys (FID) were trnsformed y pplying 4 k zero filling nd line rodening of Hz. The res for different 3 C resonnes were ssigned ording to Kniker nd Lüdemnn (995) nd Peurvuori nd Pihlj (998) into seven integrting regions s follows: ppm (liphti nd romti roxyl C, C in midi groups; roxyl/mide), ppm (oxygen sustituted romti C from lignin nd nonhydrolyzle tnnins; phenoli, O-ryl), 4 2 ppm (unsustituted nd lkyl-sustituted romti C; ryl), 93 ppm (nomeri C; di-o-lkyl), ppm (oxidized nd/ or rohydrte C; O-lkyl), ppm (minly methoxyl C; methoxyl/n-lkyl), 46 ppm (liphti C; lkyl). The re of eh spetrl region ðr s i Þ ws divided y the sum of ll spetrl res, in order to otin reltive perentge ðr % i Þ: R % i ¼ R s i Pi Rs i! The vlues were used s vriles for further nlysis. 3 C NMR derived indies (CC/MC, lkyl/o-lkyl, (ryl + O-ryl)/O-lkyl) nd the degree of hydrophoiity (HB/HI) of the sustrtes hve een lulted ording to Spini et l. (2) nd Almendros et l. (2) Miroiologil, iohemil nd enzymti nlyses Totl popultions of ulturle teri nd fungi miroil were determined ording to Lrkin nd Honeyutt (26). Miroil tivity ws ssessed y using the hydrolysis of fluoresein diette method (FDA) (Workneh et l., 993). Totl protein ontent nd N-etyl-gluosminidse tivity (NAGse), glunolyti tivity (glunse), nd hitoiosidse tivity (Bise) were determined s follows. Pets nd ompost filtrtes were otined y suspending n liquot of the orgni mteril ( g, dry weight) in sterile wter ( L) nd inuted in rotry shker (4 rpm) t 25 C. After 2 h, the suspensions were entrifuged t 6,g (Centrifuge Sorvll SC5C plus, USA) for min t 2 C. The superntnt ws removed nd onentrted to one-tenth of the initil volume in rotry evportor t 4 C (Bühi Heting Bth B-49, Switzerlnd) nd vuum memrne pump (Vuurnd GMBH + CO, Germny). The onentrted smple ws filtered through.22-lm memrne filter (Millipore, Brdford, MA, USA), nd stored t 2 C with 2% glyerol until use. Filtrtes were tested for the totl protein onentrtion y olorimetri ssy (Bio-Rd ssy), for NAGse nd glunse tivities s desried y Npolitno et l. (26), nd for Bise tivity s indited y Hrmn et l. (993). BIOLOG Ò EoPltes (BLG) provide method for determintion of ommunity-level physiologil profiling of miroil popultions sed on ron sustrte utiliztion (Biolog In., CA, USA). BLG onsist of 96 wells ontining 3 different ron soures, nd lnk in triplite. As the ron soure is utilized the tetrzolium violet dye present in the wells is redued developing purple olor. Asorne redings were tken t 59 nm with plte reder every 24 h for 96 h. Miroil tivity in eh miroplte, expressed s verge well-olor development (AWCD) ws determined s desried y Gomez et l. (26). Orgni mendment suspensions ( g of powdered dried mteril suspended in 2 ml of distilled wter) were shken (5 rpm) for 2 h t room temperture nd then entrifuged t 8g for 2 min to extrt the miroes. Superntnt ws removed nd stored t 4 C, while the preipitte ws proessed y nother extrtion yle. The seond superntnt ws dded to the first one. Aliquots of ll from this wter miroil suspension, diluted t 2 (dilution individute ðþ y preliminry experiments), were inoulted into the miropltes. The pltes were inuted t 28 C for 4 dys Sttistil nlyses Three-wy ANOVA ws pplied for eh pthogen to test the effets of ompost type, pplition rte nd steriliztion on seedling dmping-off. For this nlysis we used the verge dmpingoff ssessed t different inoulum onentrtions (%,.3%, % nd 3%). Perentge dt of dmping-off were rsine to stisfy the ssumption of normlity. The steriliztion effet of orgni sustrtes ws evluted y the rtio of dmping-off inidene in sterile/not sterile medium. Vlues ove of this rtio indite loss of suppressiveness with steriliztion, no effet nd vlues elow n inrese of suppressiveness with steriliztion. One-wy ANO- VA ws used to test differene in hemil, miroiologil nd enzymti hrteristis mong the orgni sustrtes. Finlly, the reltionships mong ll sustrte prmeters nd dmpingoff inidene were ssessed using regression nlysis. 3. Results 3.. Dmping-off disese inidene All pthogens inited high dmping-off inidene on P nd P2, with no sttistilly signifint differenes etween the two mterils (Fig. ). Dmping-off of L. stivum used y ll pthogens ws signifintly ffeted y ompost type nd steriliztion, with signifint intertion etween ompost type nd steriliztion (Tle ). Sine no signifint dose effet (% vs 2% w/w) ws oserved (Tle ), only dt t 2% were reported. Compred to P, ll five omposts signifintly redued P. ultimum inidene, three omposts (C2, C3 nd C4) ontrolled S. minor, nd two omposts (C nd C4) suppressed R. solni (Fig. ). Four omposts showed multi-suppressive properties, i.e. were ple to ontrol more Dmping-off (%) Pythium ultimum Rhizotoni solni C d Slerotini minor d d C2 C3 % C4 DO C5 P P2 Fig.. Lepidium stivum dmping-off inidene reorded fter 7 dys in not sterile ompost-mended ontiner medi (2%; open rs) ompred to non-mended pets (drk gry rs). Vlues re verge of three inoultion levels (.3%, % nd 3% w/w). Brs indite + stndrd devition of five replites; lowerse lettering indites signifint differenes (P <.5, Dunn test).

4 8 C. Pne et l. / Biologil Control 56 (2) 5 24 Tle Syntheti results of three different three-wy ANOVA of Lepidium stivum seedling dmping-off used y Pythium ultimum, Rhizotoni solni nd Slerotini minor. Effet Pythium ultimum Rhizotoni solni Slerotini minor df F P-vlue df F P-vlue df F P-vlue Compost type < < <. Applition rte Steriliztion 26.2 < <. Compost type pplition rte Compost type steriliztion < Applition rte steriliztion Compost type pplition rte steriliztion Compost type (C C5), pplition rte (% nd 2%) nd steriliztion (sterile nd not sterile medium) re the min ftors of the three nlyses. P-vlues <.5 in old type. df: degree of freedom. thn one pthogen. Speifilly, C5 suppressed only S. minor, C2 nd C3 ontrolled P. ultimum nd S. minor, C suppressed P. ultimum nd R. solni nd C4 ws le to ontrol ll the pthogens (Fig. ). Compost steriliztion (het tretment) redued mixture suppressiveness in 9 of 2 ses, wheres n inrese of disese suppression ws not reported (Fig. 2). The mgnitude of the steriliztion effet ws lrger for C4 nd C5 omposts towrds R. solni nd for C3 towrds S. minor (Fig. 2). All omposts were not phytotoxi t the pplition rte used euse not signifint growth redution ws oserved in the mended ut non-inoulted ontrols (dt not shown) Chemil nlyses nd 3 C-CPMAS-NMR spetrosopy Totl N nd TON were generlly lrger for omposts ompred to pets (Tle 2). Among omposts, C4 showed the highest nd C5 the Steriliztion effet (sterile / notsterile) Pythium ultimum Rhizotoni solni Slerotini minor C C2 C3 C4 C5 P P2 Fig. 2. Effet of sustrte steriliztion lulted s dmping-off rtio etween sterile nd not sterile medium. Vlues ove indite loss of suppressiveness with steriliztion, no effet nd vlues elow n inrese of suppressiveness with steriliztion. Asterisks indite signifint differenes from (P <.5, Dunn test). Open nd drk gry rs indite ompost-mended ontiner medi (2%) nd non-mended pets, respetively. lowest mount of N nd TON. The onentrtion of NH 4 N ws rther high in C nd C4 smples. C/N rtio ws generlly lower for omposts, rnging from 9 to 9, ompred to pets (Tle 2). Pets were suid, while ll omposts, with the exeption of C5, hve phs ove 9. Eletril ondutivity (EC) of ll smples ws reltively low, ut omposts displyed higher vlues ompred to pets (Tle 2). The mount of humi ron (C H ) nd the degree of humifition ssessed y the DH nd HR indexes reported vrile vlues mong omposts nd pets (Tle 2). The 3 C-CPMAS-NMR nlysis reveled distint differenes mong the orgni mterils, espeilly etween omposts nd pets. Pets hve more evident liphti lkyl-c region ( 46 ppm, hrteristi of lipids), nd slightly lower level of the O-lkyl-C regions (67 92 nd 93 ppm, minly ssoited with sugrs nd polyshrides). Moreover, the regions ssoited with methoxyl C (66 47 ppm) nd with roxyl C (88 65 ppm) were less developed in pets ompred to omposts, exept for C5 (Tle 3). As onsequene of these differenes, pets hve higher lkyl/o-lkyl rtio nd hydrophoiity index (HB/HI), with the exeption of ompost C3 (Fig. 3; Tle 3). The differenes of 3 C NMR spetr mong omposts were less ler-ut. Smples C2 nd C3 hve more developed lkyl-c region, wheres the O-lkyl-C regions were lrger in C5 nd smller in C3 (Tle 3). The C3 smple reported the lrgest ryl region nd the higher HB/HI index Miroiologil, iohemil nd enzymti nlyses Popultions of ulturle teri nd fungi were higher in C2 nd C3 omposts nd lowest in C smple (Tle 2). C2 nd C3 were derived from the orgni frtion of muniipl io-wstes. P nd P2 reported intermedite vlues of fungl nd teril popultions (Tle 2). Enzymti tivities nd protein ontent of P nd P2 were omprle, with the exeption of the Bise tivity tht ws higher for P (Fig. 4). In ontrst, omposts showed lrge vriility for these prmeters. In detil, Bise tivity ws low for ll omposts exept for C4 tht hs very high vlue (Fig. 4). The sme pttern ws found for NAGse tivity (Fig. 4). FDA tivity ws higher for C5 followed y C3 nd C4, while the lowest vlues were oserved for C2 nd C omposts (Fig. 4). Glunse tivity ws highest in the two pets nd C4, nd lowest in C3 nd C (Fig. 4). The protein ontent ws low for the two pets nd C5, nd high for C4 nd C omposts. Bsed on the kinetis of olor development in BLG pltes, ll omposts reported higher AWCD vlues ompred to pets (Fig. 4), with the highest vlues for C. The mximum AWCD vlues showed y P nd P2 fter 92 h of inution were only hlf of tht of the ompost with the lowest vlue (C5).

5 C. Pne et l. / Biologil Control 56 (2) Tle 2 Bsi hemil nd miroiologil properties of the five omposts (C C5) nd the two pets (P nd P2). Prmeter Smples n C C2 C3 C4 C5 P P2 N (g/ g) NH 4 N (g/ g) TON (g/ g) TOC d (g/ g) TEC e , C f H (g/ g) HI g (g/ g) DH h (%) HR i (%) C-to-N ph EC j (ds/m) W k (g/ g) Fungi l (fu/g) Bteri m (fu/g) Totl nitrogen. Ammonil nitrogen. Totl orgni nitrogen. d Totl orgni ron. e Totl extrtle ron. f Humi ron. g Humifition index = TEC C H /C HA. h Humifition degree = C H /TEC. i Humifition rtio = C H /TOC. j Eletril ondutivity. k Wter ontent. l Totl ulturle fungi. m Totl ulturle teri. n Orgni medi desription: C: omposted residues otined from vitiulture nd enologil ftory; C2: omposted orgni frtion of differentited muniipl iowste; C3: omposted orgni frtion of undifferentited muniipl io-wste; C4: omposted ow mnure; C5: medium otined from omposting mixture of 5% orgni frtion of differentited muniipl io-wste nd 5% pet; P: medium omposed of 5% light nd 5% drk Sphgnum pets nd.5 kg/m 3 PG-Mix (N, P, K); P2: medium omposed of 7% light nd 3% drk Sphgnum pets nd.5 kg/m 3 PG-Mix (N, P, K). Tle 3 Reltive undne (ppm within eh spetrum expressed s %) of the seven min groups nd reltive rtios of C types ssessed y 3 C-CPMAS-NMR spetrosopy of the five omposts (C C5) nd the two pets (P nd P2). ppm Smples C C2 C3 C4 C5 P P2 3 C NMR region Alkyl Methoxyl, N-lkyl O-Alkyl Di-O-lkyl Aryl O-Aryl Croxyl mide C NMR rtios Alkyl/O-lkyl CC/MC (Ar + O-Ar)/O-Al HB/HI Orgni medi desription: C: omposted residues otined from vitiulture nd enologil ftory; C2: omposted orgni frtion of differentited muniipl io-wste; C3: omposted orgni frtion of undifferentited muniipl io-wste; C4: omposted ow mnure; C5: medium otined from omposting mixture of 5% orgni frtion of differentited muniipl io-wste nd 5% pet; P: medium omposed of 5% light nd 5% drk Sphgnum pets nd.5 kg/m 3 PG-Mix (N, P, K); P2: medium omposed of 7% light nd 3% drk Sphgnum pets nd.5 kg/m 3 PG-Mix (N, P, K) Reltion mong sustrte prmeters nd seedling dmping-off The whole ross-orreltion mtrix, eing omposed of 38 prmeters nd indexes, produed 73 Person orreltion oeffiients (dt not shown). Herein, only the most relevnt results re desried. Conerning hemil prmeters, the different nitrogen forms (N totl nd TON) were positively uto-orrelted nd showed strong positive orreltions with ph, BLG AWCD (Person oeffiients:.84; P <.5) nd the methoxyl C region of 3 C NMR spetr (Person:.95; P <.). The C/N rtio reported strong negtive orreltions with ph (Person:.93; P <.), BLG AWCD (Person:.96; P <.) nd the roxyl C region of 3 C NMR spetr (Person:.94; P <.). Totl extrtle ron (TEC) ws negtively orrelted with C/N rtio (Person:.74; P <.5), diretly orrelted with ph (Person:.75; P <.5) nd the roxyl C region of 3 C NMR spetr (Person:.87; P <.5). Popultions of ulturle teri nd fungi were positively uto-orrelted (Person:.97; P <.), ut only sttistilly not signifint orreltions were found with other prmeters. The

6 2 C. Pne et l. / Biologil Control 56 (2) 5 24 Dmping-off inidenes used y the three pthogens (P. ultimum, R. solni nd S. minor) were not uto-orrelted (Tle 4). P. ultimum dmping-off in not sterile medium ws positively orrelted with C/N rtio nd with the O-ryl C region of 3 C NMR spetr (Tle 4). Interestingly, this lst orreltion ws lso oserved in sterile medium. Moreover, P. ultimum disese in not sterile medium ws negtively orrelted with ph, TEC nd the roxyl C region of 3 C NMR spetr (Tle 4). Dmping-off inidene used y R. solni in not sterile medium ws negtively orrelted with Bise nd NAGse tivities, NH 4 N nd totl protein ontent (Tle 4). In ontrst, signifint positive orreltion ws found in not sterile medi etween dmping-off inidene nd the lkyl/o-lkyl rtio. This orreltion ws lost in sterile medium (Tle 4). Finlly, dmping-off inidene used y S. minor in non-sterile medium ws negtively orrelted with sustrte EC (ut not in sterile medium) nd positively orrelted with the O- ryl C region of 3 C NMR spetr (Tle 4). 4. Disussion Fig C-CPMAS-NMR spetr of ompost (C C5) nd pet (P nd P2) smples. Vertil lines delimitte seven different spetrl regions: liphti nd romti roxyl C = ppm; oxygen sustituted romti C from lignin nd nonhydrolyzle tnnins, phenoli nd O-ryl = ppm; unsustituted nd lkyl-sustituted romti C, ryl = 4 2 ppm; nomeri C nd di-olkyl = 93 ppm; oxidized nd/or rohydrte C, O-lkyl = ppm; methoxyl/n-lkyl = ppm; liphti C, lkyl = 46 ppm. four enzymti tivities were not uto-orrelted, with the exeption of Bise nd NAGse tht reported strong positive orreltion (Person:.98; P <.). In ddition, Bise nd NAGse tivities were positively orrelted with the mount of NH 4 N (Person:.95; P <.). FDA tivity reported only not signifint orreltions with other prmeters. Finlly, glunse tivity reported only positive orreltion with the di-o-lkyl-c region of 3 C NMR spetr (Person:.8; P <.5). Pet mended with omposts redued disese dmping-off used y P. ultimum, R. solni nd S. minor in 9 out of 2 of the ompost pet omintions tested. This is n enourging result (for P. ultimum ll mixtures were suppressive) nd indites tht some of these omposts ould e used to rete suppressive sustrtes y prtilly sustituting pet in the potting medium. Sine the 97s, mny studies demonstrted tht ompost pplition effetively ontrols mny soilorne fungl pthogens (Nole nd Coventry, 25; Bonnomi et l., 27). However, the mjority of these erly studies exmined the pility of one or few omposts to speifilly suppress one pthogen (Trills-Gy et l., 986; Spring et l., 98). Only more reent investigtions ssessed the suppressiveness of mny omposts towrds different pthogens. For instne, Sheuerell et l. (25) ompred 36 ompost types in three different pthosystems nd Termorshuizen et l. (27) pplied 8 omposts in seven pthosystems. These studies reported tht disese suppressiveness ws rther vrile ross different omposts, nd pthogen speies. For instne, Termorshuizen et l. (27) found tht two different isoltes of the fungus R. solni, elonging to the sme nstomosis group (AG2), ssyed seprtely ginst uliflower nd pine on the sme ompost gve ontrsting responses. In ddition, vriility in growth medium suppressiveness ould e relevnt lso etween mterils otined with similr omposting proesses nd feedstok origins (Veeken et l., 25). In reent review, Bonnomi et l. (2) found tht orgni mendments were suppressive to different pthogens only in few ses, wheres in the mjority of the experiments nlyzed showed tht mteril suppressive to one pthogen ws ineffetive or even onduive to other pthogens. Results of the present study lso suggest tht ompost suppressiveness is often pthogen speifi. In ft, only ompost C4 signifintly suppressed ll pthogens, wheres C suppressed P. ultimum nd R solni ut not S. minor, C2 suppressed P. ultimum nd S. minor ut not R. solni nd, finlly, C5 effetively ontrolled P. ultimum ut not R. solni nd S. minor. All these oservtions suggest tht the identifition of ompost tht n e suppressive to ll or mny pthogens proly is not hievle. However, the prtil use of ompost suppressive to speifi pthogen ould e possile if its speifi suppressive properties n e urtely predited. Unfortuntely this is diffiult tsk. In our study L. stivum dmping-off used y P. ultimum ws suppressed y C2 nd C3 omposts, independently from steriliztion tretment. This suggests tht the ioti omponent of these omposts plys limited role, if ny, in pthogen suppression. Similrly Psul et l. (22) reported tht the humi frtion of

7 C. Pne et l. / Biologil Control 56 (2) % ompred to P (=) NAGse %vsp d d d Bise Protein d Glunse C C2 C3 C4 C5 P P2 C C2 C3 C4 C5 P P2 FDA AWCD Fig. 4. Enzymti tivities (glunse; N-etyl-gluosminidse, NAGse; hitoiosidse, Bise; nd hydrolysis of fluoresein diette, FDA), totl protein ontent nd metoli tivity mesured y Biolog EoPlte (verge well-olor development, AWCD) of the five omposts (open rs) nd the two pets (drk gry rs). Brs indite + stndrd devition, lowerse lettering indites signifint differenes (One-wy ANOVA: P <.5, Dunn test). muniipl solid wste ws effetive in ontrolling P. ultimum on Pisum stivum, lso in sterile onditions. In ontrst with C2 nd C3 smples, omposts C, C4 nd C5 lost prt of their suppressiveness fter steriliztion, suggesting tht their ioti omponent plyed signifint role. The ontrol of Pythium hs een often relted to the generl suppression model, whih supposes tht rod vriety of miroil speies rete ompetitive environment for pthogens (Bker nd Cook, 974). In this ontext, promising prediting prmeter ws the FDA tivity tht in severl studies resulted positively orrelted with Pythium suppressiveness (Chen et l., 988; Stone et l., 2). However, this model ws not supported y Erhrt et l. (999), nd this study lso showed tht FDA tivity ws not orrelted with P. ultimum suppression. The signifint negtive orreltion etween TEC nd ph with P. ultimum dmping-off ould e explined euse the ondutive pets hve lower ph nd TEC vlues ompred to suppressive omposts. In previous study, Boehm et l. (997), using 3 C NMR spetrosopy, demonstrted tht pet suppressiveness to P. ultimum dereses with pet ge euse of the progressive depletion of rohydrtes nd esily degrdle orgni ompounds tht re neessry to sustin iologil ontrol gents. For omposts, we found herein more omplex senrio. P. ultimum dmping-off ws positively nd negtively orrelted with the ryl nd the roxyl C regions of the 3 C-CPMAS-NMR spetr of orgni ompounds, respetively. Although this is new nd interesting finding, its eologil signifine should e eluidted nd ssoited with the tivity nd struture of the resident miroil ommunities. In onlusion, this work indites tht ompost suppressiveness is sed on different mehnisms, of oth ioti nd ioti origin, nd tht further studies re required to identify prmeters onsistently orrelted with P. ultimum suppressiveness. In generl term, R. solni is onsidered to e the most prolemti pthogen sine its ontrol with omposts is rre phenomenon (Kruse et l., 2; Sheuerell et l., 25; Bonnomi et l., 27), nd disese suppression is errti nd lmost unpreditle (Termorshuizen et l., 27; Bonnomi et l., 2). Sheuerell et l. (25), for instne, found tht only 7% of the ssyed omposts (n = 36) suppressed R. solni, nd tht none of the 5 physil, hemil nd iologil mesured prmeters provided signifint orreltions with disese inidene. In this study, the two suppressive omposts, C nd C4, preserve or entirely lost their suppressiveness fter steriliztion, respetively, suggesting tht the underlying mehnisms of pthogen suppression were different. The signifint negtive orreltion etween NAGse nd Bise with dmping-off is due to the C4 smple whih hd the highest enzymti tivities. Severl studies demonstrted tht R. solni ontrol is prtilly due to the speifi tion of suh extrellulr lyti enzymes produed y ntgonists miroes (Jung et l., 23). The speifiity of this mehnism is onsistent with the model of speifi suppression proposed for R. solni (Hoitink nd Boehm, 999). In ontrst with C4 smple, the mehnism(s) tht suppress R. solni in C ompost is proly different. In ft, this mteril hd very low NAGse nd Bise tivities, ut hd the highest totl protein nd NH 4 N ontent. This might explin the highly signifint negtive orreltion etween dmping-off nd totl protein nd NH 4 N ontent. However, NH 4 N hs no fungitoxi properties s does NH 3 (Tenut nd Lzrovits, 24) nd, onsequently, diret role in R. solni suppression seems unlikely. Interestingly, we found signifint positive orreltion in not sterile medium etween dmping-off inidene nd the lkyl/o-lkyl rtio, orreltion tht ws lost in sterile medium. The lkyl/o-lkyl rtio is onsidered s sensitive index of the stiliztion nd humifition of orgni mtter. An inrese of this rtio is interpreted s the result of progressive degrdtion of rohydrte nd orresponding inrese of miroil derived lipid io-mromoleules (Almendros et l., 2). As this index inreses, the io-vilility of rohydrtes, suh s ellulose, progressively dereses euse they re onsumed y miroes nd the remining frtion is proteted from deomposition, eing enlosed in lignin whih is more resistnt to miroil deomposition (Berg nd MClugherty, 23). The limited rohydrte io-vilility

8 22 C. Pne et l. / Biologil Control 56 (2) 5 24 Tle 4 Correltion mtrix etween hemil, miroiologil, 3 C-CPMAS-NMR derived nd enzymti prmeters of the five omposts nd the two pets nd dmping-off inidene. Vlues re Person oeffiients; sttistil signifines re from regression nlysis (underline, P <.5; old, P <.). Pythium unsterile Pythium sterile Rhizotoni unsterile Rhizotoni sterile Slerotini unsterile Slerotini sterile Chemil nd miroiologil ph EC Wter ontent N totl NH 4 N TON TOC TEC CH d HI e DH% f HR% g C/N Fungi Bteri C NMR Alkyl Methoxyl O-Alkyl Di-O-lkyl Aryl O-Aryl Croxyl Alkyl/O-lkyl CC/MC h (Aryl + O-ryl)/O-lkyl HB/HI i Enzymti Protein Glunse NAGse Bise FDA Biolog (AWCD) Diseses Pythium unsterile Pythium sterile Rhizotoni unsterile Rhizotoni sterile.38.5 Slerotini unsterile.77 Totl orgni nitrogen. Totl orgni ron. Totl extrtle ron. d Humi ron. e Humifition index = TEC CH/CHA. f Humifition degree = CH/TEC. g Humifition rtio = CH/TOC. h CC/MC (Spini et l., 2). i HB/HI, hydrophoi index (Spini et l., 2). proly impirs the ility of R. solni, speies ple of exploiting ellulose s ron soure (Ppvizs, 97), to inite the disese. The io-vilility of rohydrte is onsidered ruil for suppression of Pythium (Hoitink nd Boehm, 999) nd R. solni (Tuitert et l., 998). Compred to Pythium spp. nd R. solni, fewer studies hve investigted the possiility of ontrol S. minor with omposts (Bonnomi et l., 27), nd only few report signifint disese suppression (Lumsden et l., 983, 986). Consequently, very little informtion is ville to predit disese inidene y this pthogen. Lumsden et l. (986) reported tht S. minor suppression fter ompost pplition ws positively orrelted with FDA tivity, ut Bonnomi et l. (28) reported n opposite trend fter soil mendment with plnt residues (Medigo stiv L. strw). In this work, the FDA tivity ws not relted to dmping-off inidene. However, for ll suppressive omposts (C2, C3 nd C4) prt of their suppressiveness ws lost fter steriliztion, suggesting signifint role of the ioti omponent. Of the 8 prmeters ssessed to hrterize the different ompost, only two showed mrginlly signifint orreltion with S. minor dmping-off: the O-ryl region of the 3 C-CPMAS-NMR spetr nd sustrte EC. It is noteworthy, tht the negtive orreltion etween dmping-off nd EC ws lost in sterile medium. This result suggests high sensitivity of S. minor to sustrte slinity, ut only in the presene of ntive miroil ommunity ple to ompete with the pthogen. However, it is known tht

9 C. Pne et l. / Biologil Control 56 (2) ompost hemistry nd miroiology n e ltered sustntilly during utolving tretment with hnges in lile orgni mtter nd minerl nitrogen forms (Tilston et l., 22). Finlly, it is interesting to note tht the informtion gthered from the ron-soure utiliztion profile of the BLG method, though eing ple of distinguishing etween pets nd omposts ould not disriminte suppressive from non-suppressive omposts for ny of the studied pthogens. In this ontext, it is importnt to rell tht while it is importnt to identify speifi hrteristis onsistently ssoited with suppressive omposts, it is eqully importnt, s summrized in this work, to reognize vriles unrelted to disese suppression (Tle 4). 5. Conlusions Pet mendments with ompost hve gret potentil for the ontrol of soilorne pthogens, ut their inonsistent performnes still limit their wide use. There is no dout tht the enefiil effets of ompost mendments fr outweigh their detrimentl effets. However, s long s the impt of this tehnique on disese suppression remins unpreditle, frmers my e justified in ignoring it s tool for soilorne pthogen ontrol. A strong effort hs een mde in the lst dede to serh for relile inditors of ompost suppressiveness (Bonnomi et l., 2). Reent studies ddressed this topi y hrterizing lrge numer of ompost smples for hemil, iohemil nd miroiologil fetures serhing for prmeters onsistently orrelted with disese suppression (e.g. Erhrt et l., 999; Sheuerell et l., 25; Termorshuizen et l., 27). This work provides some indition for the predition of suppressiveness of different omposts for P. ultimum (e.g. TEC, O-ryl C), R. solni (lkyl/o-lkyl rtio; NAGse nd Bise enzymti tivities) nd S. minor (EC). However, it is evident tht ny one vrile lone nnot e relile nd onsistent prmeter for prediting suppressiveness of ll different OM mendments versus ll soilorne pthogens. This likely ours euse the mehnisms of disese suppression re different nd there my e mny vriles tht need to e simultneously monitored. This piture is further omplited y the lrge vriility oserved mong nd even within ompost types nd the often reported different response mong pthogen isoltes of the sme speies (Termorshuizen et l., 27). Future studies re required to evlute the reliility of the prmeters proposed s inditors of suppressive ompost, nd to identify generl priniples ple to provide guidelines to predit the impt of ompost mendment on soilorne diseses. Aknowledgments The uthors knowledge the Itlin ftories tht provided omposts nd pet mixes. We thnk the CERMANU-Interdeprtmentl Reserh Centre, University of Npoli Federio II, for 3 C-CPMAS-NMR mesurements. Referenes Almendros, G., Dordo, J., González-Vil, F.J., Blno, M.J., Lnkes, U., 2. 3 C NMR ssessment of deomposition ptterns during omposting of forest shru iomss. Soil Biology & Biohemistry 32, Bker, K.F., Cook, R.J., 974. 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