Effect of AVG Application on Fruit Set, Yield and Fruit Size in Abate Fetel and Packam s Triumph Pears in a Semi-Commercial Statistical Trial

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1 Effect of AVG Appliction on Fruit Set, Yield nd Fruit Size in Ate Fetel nd Pckm s Triumph Pers in Semi-Commercil Sttisticl Tril E. Sánchez nd M. Curetti Instituto Ncionl de Tecnologí Agropecuri Estción Experimentl Agropecuri Alto Vlle CC 782, Generl Roc (8332), Río Negro Argentin J. Retmles Vlent BioSciences Av. Kennedy 5735, Of Ls Condes, Sntigo Chile Keywords: Pyrus communis, minoethoxyvinylglycine, Aè Fetel, June drop, crop lod, ethylene Astrct Fruit set in per (Pyrus communis L.) cn e low nd unpredictle. The im of this study ws to increse fruit set nd susequently yield in Ate Fetel (AF) nd Pckhm s Triumph (PT) pers. The influence of minoethoxyvinylglycine (AVG) ppliction ws investigted in semi-commercil sttisticl tril in Río Negro, Argentin in the seson. The pplictions were rndomly performed on eight rows t two stges of growth (full loom nd 14 dys fter full loom) nd two rtes (125 nd 250 mg L -1 ) with n untreted control. Appliction volume ws set t 500 L h -1 in order to mke the ppliction economiclly ffordle for growers. Fruit drop, fruit set 60 DAFB, numer of fruit per cm 2 rnch cross sectionl re, fruit size (weight, width, height), numer of seeds per fruit nd yield were evluted. AVG 250 mg L -1 tretment t full loom reduced yield in oth cultivrs (12% in PT nd 8% in AF). However, tretments t 14 dys fter full loom improved fruit set in oth cultivrs, ut only the higher rte ws effective in PT. In this cultivr, 22% increse in fruit set nd 33% increse in yield were recorded with AVG ppliction t 250 mg L -1. In AF, AVG 14 dys fter full loom reduced fruit drop t 30 DAFB, improved fruit set (65%) nd yield (16%), especilly during the first hrvest. We conclude tht AVG t 250 mg L -1 pplied two weeks fter full loom cn increse fruit set nd yield in the cultivrs PT nd AF. INTRODUCTION Flowering time is crucil period in per trees ecuse good yield is dependent on good fruit set (Vercmmen nd Gomnd, 2008). Poor pollintion, impired ovule development, vegettive competition nd some environmentl conditions cn cuse excessive drop of young fruit (Wlsh nd Fust, 1982). In the Alto Vlle re in Argentin, severe per drop usully occurs etween 3 nd 6 weeks fter loom. Ethylene is involved in the senescence nd scission of flowers (Greene, 1980). Among ethylene iosynthesis inhiitors, the most effective nd commonly used is minoethoxyvinylglycine (AVG) (Yng, 1980). First AVG studies in order to increse fruit set were mde on pple in the USA (Willims, 1980; Greene, 1980, 1983; Edgerton, 1981; Wlsh nd Fust, 1982; Child nd Willims, 1983). A solution of 1000 mg L -1 AVG spryed 14 dys fter full loom mrkedly incresed fruit set in Delicious nd Golden Delicious pples, lthough this rte ppered to e considerly higher thn necessry (Willims, 1980). In fct, Greene (1980) nd Edgerton (1981) otined fruit set increse in these cultivrs with lower AVG rte, i.e., 200 mg L -1. Wlsh nd Fust (1982) evluted different AVG rtes ( mg L -1 ) spryed t full loom in young Delicious pple trees. The optiml rnge of AVG rte to increse yield ws etween 150 nd 225 mg L -1. Besides eing more expensive, higher AVG rtes (ove 500 mg L -1 ) lso diminished lef growth (Willims, 1980; Edgerton, 1981; Wlsh nd Fust, 1982). In order to e effective, AVG must e pplied within 2 to 3 weeks fter full loom, prior to the initition of June drop (Willims, Proc. 11 th Interntionl Per Symposium Eds.: E. Sánchez et l. Act Hort. 909, ISHS

2 1980; Greene, 1983). Greene (1983), found in Delicious pples tht 250 mg L -1 AVG ppliction t full loom incresed fruit set more thn pplictions mde 14 dys efore or 7 nd 14 dys fter full loom. AVG pplictions lso hve een evluted on per trees (Edgerton et l., 1981; Lomrd nd Richrdson, 1982; Dussi et l., 2002; Lfer, 2008). Edgerton et l. (1981) evluted AVG ppliction t full loom in Willims nd Pckhm s Triumph, while Lomrd nd Richrdson (1982) evluted AVG ppliction on Comice t different phenologicl stges nd rtes (150, 300 nd 600 mg L -1 ). In contrst to results in pple, the most effective time for incresing fruit set in per ws post loom. High AVG rte (600 mg L -1 ) cused lef dmge in per, consistent with the response in pple (Lomrd nd Richrdson, 1982). A solution with 200 mg L -1 of AVG pplied 14 dys fter full loom incresed fruit set in Pckhm s Triumph per in Argentin (Dussi et l., 2002), while higher rte (400 mg L -1 ) generted some injury to leves nd reduction in shoot growth. In Austri, AVG 125 mg L -1 pplied t fding flowering significntly improved fruit set nd yield in Willims per (Lfer, 2008). The im of this study ws to increse fruit set nd susequently yield in Ate Fetel nd Pckhm s Triumph per through AVG pplictions in semi-commercil sttisticl tril. MATERIALS AND METHODS The tril ws conducted in commercil orchrd plnted in 1995 (39 01 S; W, 242 m.s.l., 244 mm nnul rin, 15 C nnul verge temp.). Ate Fetel (AF) pers on seedling rootstock were plnted in hedge row system t spcing of m (1667 trees h -1 ) nd Pckhm s Triumph (PT) pers on seedling rootstock were plnted t 4 3 m (833 trees h -1 ). AVG (Retin TM ) pplictions were performed t two stges of growth (full loom nd 14 dys fter full loom) t two rtes (125 nd 250 mg L -1.i.) with n unspryed control. Ech tretment ws rndomly pplied to eight rows nd ppliction volume ws set t 500 L h -1 in order to mke the ppliction economiclly ffordle for growers. The rows were used s plots in completely rndom design. Fruit drop t spur level ws recorded weekly while fruit set ws determined in Decemer. Fruit set ws clculted s numer of fruit persisting t the end of the June drop period per 100 lossom clusters nd cm 2 cross sectionl rnch re. Fruit size (weight, width, height) ws mesured in Ferury nd yields per plot were determined t hrvest in Mrch. Dt were nlyzed y the ANOVA procedure, using Infostt softwre. Sttisticl significnce ws judged t p<0.05. When the nlysis ws sttisticlly significnt, the DGC test for seprtion of mens ws performed. For non-norml distriuted vriles, nonprmetric ANOVA Kruskl Wllis ws performed. RESULTS AND DISCUSSION Fruit Set The ppliction of AVG 14 dys fter full loom significntly incresed fruit set in oth cultivrs (Figs. 1 nd 2). In PT, AVG t 250 mg L -1 incresed fruit set y 22% expressed s numer of fruit per 100 lossom clusters nd significntly improved the numer of fruit per cm 2 rnch cross sectionl re, in greement with Dussi et l. (2002). In AF, AVG t 250 mg L -1 modestly reduced fruit drop in the first 30 dys fter loom (Fig. 3) ut mrkedly incresed fruit set y the eginning of Decemer (65%). Full loom pplictions were not very effective (Figs. 1 nd 2). In these per cultivrs, post-loom pplictions were more effective thn full loom pplictions, s ws found y Lomrd nd Richrdson (1982) for Comice. Yield nd Fruit Size AVG t 250 mg L -1 t full loom reduced the yield in oth cultivrs (12% in PT nd 8% in AF) (Tles 1 nd 2). In AF, trees treted t full loom yielded the smllest 436

3 fruits, sed on 5% shorter length thn control fruits (Tle 2). Lomrd nd Richrdson (1982) lso found smller fruit size in Comice per trees treted with AVG t full loom. AVG t 250 mg L -1 pplied 14 dys fter full loom significntly improved yield in oth cultivrs (33% in PT nd 16% in AF). In PT, fruit size in terms of verge fruit weight nd dimeter responded to fruit set, lthough not significntly. A higher fruit set ws ssocited with smller fruit size (Fig. 1 nd Tle 1). On the other hnd, post-loom treted AF trees yielded lrger fruits (Tle 2). CONCLUSION We conclude tht AVG t 250 mg L -1 pplied two weeks fter full loom incresed fruit set nd yield in per cultivrs Pckhm s Triumph nd Ate Fetel in Argentin. ACKNOWLEDGEMENTS This reserch ws supported y Vlent BioSciences. The technicl ssistnce of Fredis Cezs is gretly pprecited. Literture Cited Child, R.D. nd Willims, R.R The effects of the interctions of minoethoxyvinylglycine (AVG) with mixtures of plnt growth regultors on fruit set nd shpe of Cox s Ornge Pippin pple. J. Hort. Sci. 58: Dussi, M.C., Sos, D. nd Clvo, G Effects of Retin TM on fruit mturity nd fruit set of per cultivrs Willims nd Pckhm s Triumph. Act Hort. 596: Edgerton, L.J., Veinrnts, N. nd Miller, P Some effects of AVG nd Promlin on Brtlett nd Pckhm pers. Act Hort. 120:246. Edgerton, L.J Some effects of minoethoxyvinylglycine, 6-enzylmino purine nd gierellins on fruit set nd vegettive growth of pple. Act Hort. 120: Greene, D.W Effect of silver nitrte, minoethoxyvinylglycine nd gierellins A 4+7 plus 6-enzylminopurine on fruit set nd development of Delicious pples. J. Amer. Soc. Hort. Sci. 105: Greene, D.W Some effects of AVG on fruit set, fruit chrcteristics nd vegettive growth of pple trees. J. Amer. Soc. Hort. Sci. 108: Lfer, G Effects of different ioregultor pplictions on fruit set, yield nd fruit qulity of Willims pers. Act Hort. 800: Lomrd, P.B. nd Richrdson, D.G Increse fruit set nd cropping of Comice per trees with n ethylene inhiitor minoethoxyvinylglycine. Act Hort. 124: Vercmmen, J. nd Gomnd, A Fruit set of Conference : smll dose of gierellins or Reglis. Act Hort. 800: Wlsh, C.S. nd Fust, M AVG increses the yield of young Delicious pple trees. HortScience 17: Willims, M.W Retention of fruit firmness nd increse in vegettive growth nd fruit set of pples with minoethoxyvinylglycine. HortScience 15: Yng, S.F Regultion of ethylene iosynthesis. HortScience 15:

4 Tles Tle 1. Effect of timing nd rtes of minoethoxyvinylglycine (AVG) pplictions on fruit size nd yield t hrvest of Pckhm s Triumph s per trees. Tretment Yield Fruit weight Fruit dimeter (ton/h) (g) (mm) Control mg/l - FB z mg/l - FB mg/l - Doule mg/l - 14 DAFB y mg/l - 14 DAFB 75.2 c * * * NS x * p-vlue z FB: full loom. y DAFB: dys fter full loom. nonprmetric ANOVA Kruskl Wllis. NS: No significnt difference. *. *** Significntly different t 5% nd 0.1% level, respectively. Sme letter within columns does not differ significntly with DGC test. Tle 2. Effect of timing nd rtes of minoethoxyvinylglycine (AVG) pplictions on fruit size nd yield of Ate Fetel per trees. Yield (ton/h) Fruit Fruit Tretment 1 st hrvest Mrch 1 2 nd hrvest Mrch 8 weight (g) dimeter (mm) Fruit length (mm) Control mg/l- FB Z mg/l- FB mg/l- Doule mg/l- 14DAFB y mg/l- 14 DAFB 56.2 c * * * * * * * NS * * p-vlue z FB: full loom. y DAFB: dys fter full loom. NS: No significnt difference. **. *** Significntly different t 1 nd 0.1% level, respectively. Sme letter within columns does not differ significntly y DGC test. 438

5 Figures 75 5,0 Fruit per 100 lossom clusters ,0 3,0 2,0 1,0 Fruit per cm2 BCSA 0 Control 250 mg/l FB 125 mg/l Doule 250 mg/l 14DAFB 125 mg/l FB 125 mg/l 14DAFB 0,0 Fruit per 100 lossom clusters (NS) Fruit per cm2 BCSA (* *) Fig. 1. Fruit set of Pckhm s Triumph per trees treted with minoethoxyvinylglycine (AVG) t full loom (FB) nd/or 14 dys fter full loom (14DAFB) expressed s fruit numer per 100 lossom clusters nd fruit numer per cm 2 of rnch cross sectionl re (BCSA). NS: No significnt difference. ** Significntly different t 1% level. Sme letter does not differ significntly with DGC test ,0 Fruit per 100 lossom clusters c 4,0 3,0 2,0 1,0 Fruit per cm2 BCSA 0 Control 250 mg/l FB 125 mg/l Doule 250 mg/l 14DAFB 125 mg/l FB 125 mg/l 14DAFB 0,0 Fruit per 100 lossom clusters (* * *) Fruit per cm2 BCSA (NS) Fig. 2. Fruit set on Ate Fetel per trees treted with minoethoxyvinylglycine (AVG) t full loom (FB) nd/or 14 dys fter full loom (14 DAFB) expressed s fruit numer per 100 lossom cluster nd fruit numer per cm 2 of rnch cross sectionl re (BCSA). NS: No significnt difference. *** Significntly different t 0.1% level. Sme letter does not differ significntly with DGC test. 439

6 Fruit / 100 lossom clusters Control AVG 250 ppm t FB AVG 250 ppm 14 DAFB AVG 125 ppm t FB + 14 DAFB Dys fter full loom Fig. 3. Effect of timing nd rtes of minoethoxyvinylglycine (AVG) pplictions on fruit set nd the kinetics of fruit scission of Ate Fetel pers. Fruit set mens on the sme dy followed y different letter re significnt t 5% level. LSD Fisher. 440