Journl of Horticulturl Science & Biotechnology (7) 82 () 83 87 Plnt growth regultors increse the fruit size of Spdon nd Cosci pers (Pyrus communis) in wrm climte By RAPHAEL A. STERN 1 *, ISRAEL DORON 2 nd RUTH BEN-ARIE 3 1 MIGAL, Glilee Technology Center, P.O. Box 831, Kiryt-Shmon 116, Isrel 2 Extension Service, Ministry of Agriculture, Kiryt-Shmon, Isrel 3 Fruit Storge Reserch Lortory, Kiryt-Shmon, Isrel (e-mil: Rffi@migl.org.il) (Accepted 7 June 7) SUMMARY The two min per cultivrs grown in the wrm climte of Isrel, Spdon nd Cosci, produce reltively smll fruit. Over five consecutive yers (1 ), the ppliction of.12% (v/v) Bolero TM [8.6 mg l 1 gierellic cid (GA 3 ) plus 6 mg l 1 2,4-dichlorophenoxycetic cid (2,4-D) plus 6 mg l 1 nphthlenecetic cid (NAA)] t full-loom, cused n pprecile nd significnt increse in fruit size without ny deformtion of the clyx-end, which is typicl of GA 3 tretment when pplied t the sme phenologicl stge to improve fruit set. GA 3 lone did not increse fruit size. Appliction of.1% (v/v) Perln TM [ mg l 1 enzyldenine (BA) plus mg l 1 GA 4+7 ] t full-loom + 14 d, incresed fruit size vi stimultion of fruit cell division (BA) nd fruit cell enlrgement (GA 4+7 ), with no negtive effect on fruit shpe. The per cultivrs Spdon nd Cosci produce reltively smll fruit when grown in the wrm climte of Isrel. The verge dimeter of Spdon fruit is mm, while Cosci verges only mm. Since consumers prefer lrger pers (Looney, 1993; Flishmn et l., 1; Stern nd Flishmn, 3), fruit size ecomes n importnt mrketing prmeter. Two commercil prctices re commonly pplied to enlrge fruit. One is the indirect method of thinning flowers or fruitlets with uxin sprys, such s nphthlene cetmide (NAD; Westwood, 1993; Artec, 1996; Jckson, 3). Those fruitlets tht remin on the tree develop more rpidly s result of reduced competition for ssimiltes, s with pples (Byers, 3). The second method hs direct effect on ll the fruit on the tree, with or without thinning, nd involves the ppliction of N-(2-chloro-4-pyridyl)-N-phenylure (CPPU; Stern et l., 2), enzyldenine (BA; Stern nd Flishmn, 3), or thidizuron (TDZ; Stern et l., 3), which enhnce nd extend cell division (Shrgl et l., 6). Thus, the numer of cells in the fruit is incresed, cusing n increse in fruit size, s hs een shown in pple (Stern et l., 6) nd persimmon (Iti et l., 199). The ppliction of gierellins to pple nd per hs een shown to ffect fruit shpe vi their effects on cell enlrgement (Westwood, 1993; Artec, 1996; Jckson, 3). Loclised ppliction of GA 4 or GA 7 on one side of either of these fruit, t out 2 weeks fter full loom, resulted in cell enlrgement nd ccelerted the growth of the treted side, thus producing symmetric fruit (Bukovc nd Nkgw, 1968). A similr response of pple to GA 3, primrily cusing elongtion t the lossom-end of the fruit, ws reported y Westwood nd Bjornstd (1968). Vrious GA pplictions to grpe t full loom, or few dys therefter, drmticlly *Author for correspondence. incresed the erry size of prthenocrpic fruit, where there is deficiency in endogenous gierellin (Christodoulou et l., 1968). On the other hnd, there re numer of fruit species, such s pricot, pech nd pple, where no correltion hs een found etween the level of endogenous gierellins in fruit tissues nd totl fruit growth (Wever, 1972; Jckson nd Coome, 1966). The comintion of gierellins nd uxins hs een shown to hve synergistic effect on the growth of tomto fruit (Luckwill, 199), proly y the stimultion of endogenous uxin levels y gierellin (Sstry nd Muir, 1963). It seems tht oth plnt growth regultors (PGR) ccelerte fruit growth (Artec, 1996). The comintion of cytokinins nd gierellins is lso of interest with regrd to fruit enlrgement, s ech of them ffects different spect of fruit growth: cytokinins increse cell division (Westwood, 1993; Artec, 1996; Jckson, 3; Dvis, 4), while gierellins increse cell elongtion (Bukovc nd Nkgw, 1968; Artec, 1996). As result, one cn otin either elongted fruit (Westwood, 1993), or roder fruit, especilly t the lossom-end (Westwood nd Bjornstd, 1968). A comintion of cytokinin nd gierellin hs een shown to enlrge pples, prticulrly Delicious, y extending oth fruit length nd width t the lossom-end (Willims nd Sthley, 1969; Unrth, 1974). More recently, similr results hve een chieved with Jpnese per y comining cytokinin nd gierellin ppliction (Ohkw et l., 6; Koyshi et l., 6). Gierellin (t rte of 2 mg l 1 GA 3 ) is lso pplied commercilly to increse fruit set in per (Westwood, 1993), especilly when the conditions for pollintion nd fertilistion re not optimum (Stern et l., 4). However, n undesirle outcome of this tretment is n exggerted, often symmetricl, thickening of the fruit t its lossom-end, similr to the effect on Delicious pple mentioned ove.
84 Incresing per fruit size In the present study, we ttempted to increse the fruit size of pers, without concomitnt deformtion of the fruit, y comining the GA 3 pplied to increse fruit-set, with other gierellins, cytokinins nd uxins. MATERIALS AND METHODS The orchrds Experiments were conducted etween 1 with mture Spdon nd Cosci per trees grfted on Quince A (Cydoni olong Mill.) rootstock in four orchrds: (i) Jontn, locted 4 m ove se level (.s.l.) on the Goln Heights, where ll trees were 3 m high, spced t 2. m 4. m for Spdon, nd 2. m 4. m for Cosci ; (ii) Rmt-Mgshimim, locted 3 m.s.l. on the Goln Heights, where ll trees were 3. m high, spced t 2. m 4. m; (iii) Rosh-Pin, locted 4 m.s.l. on the Est of the Upper Glilee, where ll trees were 3. m high, spced t 2. m 4. m; nd (iv) Zrit, locted 6 m.s.l. on the West of the Upper Glilee, where ll trees were 3.2 m high, spced t 2. m 4. m. All the orchrds were locted in semi-rid region with high tempertures (c. 3ºC mx.) nd low humidity (< 4% RH) during the Summer (My Octoer). Annul precipittions (Novemer April) were pprox. 4,, 6 nd 8 mm t Jontn, Rmt-Mgshimim, Rosh- Pin nd Zrit, respectively. The soil ph ws 7. 7.7 in ll orchrds, with CCO 3 contents of pprox. 7% (w/w). PGR ppliction Four commercil products, contining different comintions of synthetic uxins, cytokinins or gierellins (GA) were pplied: (1) ProGi, liquid formultion contining 3.2% (v/v) GA 3, mnufctured y Aott Lortories, Chicgo, IL, USA; (2) Bolero TM, liquid formultion contining 7% (v/v) GA 3, % (v/v) dichlorophenoxycetic cid (2,4-D isopropyl ester) nd % (v/v) nphthlenecetic cid (NAA), mnufctured y Linco, Brcelon, Spin; (3) Perln TM, liquid formultion contining 1.8% (v/v) enzyldenine (BA) nd 1.8% (v/v) GA 4+7, mnufctured y Fine Agrochemicls, Whittington, UK; nd (4) Bongrow TM, liquid formultion contining 4% (v/v) BA, mnufctured y Sfe-Pck, Kefr-S, Isrel. The synthetic gierellins were pplied t concentrtions close to the commercil recommendtion for incresing fruit set ( mg l 1 GA 3 ): ProGi t 9 or mg l 1 GA 3 ; nd Bolero TM t 8.6 mg l 1 GA 3 (.12% Bolero TM ). The other two products (Perln TM nd Bongrow TM ) contining BA, with or without GA 4+7, were pplied s follows: Perln TM t or mg l 1 BA nd GA 4+7, respectively; nd Bongrow TM t mg l 1 BA. All products were pplied s folir sprys. A non-ionic surfctnt, Triton X-, ws included in ll sprys t.%(v/v). Appliction ws done t full-loom (FB), unless stted otherwise. The experiments were conducted on whole trees ering uniform crop lod. Three to l per tree ws spryed with high-pressure hndgun spryer (Kiutz Degni, Isrel) until run-off. trees, with the sme crop lod, were not spryed. The experimentl design ws s rndomised complete locks, with eight replictions nd one tree per tretment in ech lock. At hrvest, the yield from ech tree ws weighed nd ll fruit were sorted y dimeter into smll (< mm), medium ( mm), nd lrge (> mm) for Cosci ; or smll (< mm), medium ( 6 mm), nd lrge (> 6 mm) for Spdon. When the totl yield of Spdon fruit ws low, the fruit size distriution ws shifted to the lrger size rnge. In such cses, fruit size ws reclssified s smll (< 6 mm), medium, (6 6 mm), nd lrge (> 6 mm). A semi-commercil tril ws lso conducted with Spdon trees in the Rosh-Pin orchrd, in 4 using commercil 1, l ir-lst Spidet lower spryer (Kiutz Degni) t spry volume of 1, l h 1.The experimentl design used here ws rndomised complete locks with four replictes. Ech replicte consisted of trees. At hrvest, totl fruit yield nd verge fruit size were determined for ll trees. Fruit shpe nd seed numer In 4, 4 fruit per tree from the lrge size clss of Spdon were hrvested t rndom in the orchrd t Jonthn. The numer of seeds ws counted in ll fruit smples, nd the fruit were rted nd designted s hving either norml, or n norml shpe t their lossom-end. Sttisticl nlysis Percentge dt were sujected to rcsine trnsformtion efore nlysis, to provide norml distriution. Dt were nlysed for sttisticl significnce y mens of the generl liner model (GLM) procedure. Duncn s new multiple rnge test ws used to compre tretments when nlysis of vrince showed significnt differences mong mens. Sttisticl Anlysis Systems Softwre for PC (SAS Institute, Cry, NC, USA) ws used to nlyse these dt. RESULTS AND DISCUSSION Fruit size nd yield In preliminry experiment, conducted in 1, it ws found tht high concentrtion of.% (v/v) Bolero TM (GA 3 + 2,4-D + NAA t. mg l 1, 7. mg l 1 nd 7. mg l 1, respectively) cused lef scorching, wheres low concentrtion of.1% (v/v) Bolero TM (GA 3 + 2,4-D + NAA t 7. mg l 1,. mg l 1 nd. mg l 1, respectively) hd no impct on fruit size (dt not shown). Therefore we continued ll our experiments with.12% (v/v) Bolero TM (8.6 mg l 1 GA 3 + 6 mg l 1 2,4-D + 6 mg l 1 NAA). In the second yer (2), we exmined the effectiveness of.12%(v/v) Bolero TM in two different orchrds: one with low yield (Rosh-Pin), nd the second with high yield (Rmt-Mgshimim). In oth orchrds there ws significnt increse in the yield of lrge fruit (Tle I). However, the increse in the low yield orchrd ws greter (1%; from. to 11. kg tree 1 ) thn in the high yield orchrd (42%; from 19 to 27 kg tree 1 ). This result ws proly due to ssimilte limittion in the high yield orchrd, which could not produce sufficient ssimilte to increse the size of ll the lrge numer of fruit (Byers 3; Greene, 3; Stern et l., 6). In commercil orchrds, fruit size is incresed primrily y reducing the crop lod using chemicl thinner. Thus, lthough the totl yield is reduced, the remining fruit re lrger (Forshey, 1986).
R. A. STERN,I.DORON nd R. BEN-ARIE 8 TABLE I Effects of Bolero TM on fruit size nd yield of Spdon per in two orchrds in 2 Tretment Totl yield Yield of lrge (> 6 mm) Increse in lrge fruit yield Orchrd Bolero TM [.12% (v/v)] (kg tree 1 ) fruit (kg tree 1 ) (kg tree 1 ) (%) Rosh-Pin 17. + 27 11. 6. 1 Rmt-Mgshimim 3 19. + 61 27. 8. 42 Men vlues within column followed y different lower-cse letter for ech orchrd differ significntly ccording to Duncn s new multiple rnge test, P =.. Bolero TM,.12% (v/v) = 8.6 mg l 1 GA 3 + 6 mg l 1 2,4-D + 6 mg l 1 NAA. In the third yer (3), we exmined the effects of.12%(v/v) Bolero TM on the cultivr Cosci in the Jonthn orchrd, nd re-exmined the tril with Spdon in different re, t Zrit. We pplied mg l 1 GA 3 lone s the stndrd tretment to improve fruit set in per. The results for Cosci showed tht lthough the totl yield ws similr in oth tretments (pprox. 4 kg tree 1 ), Bolero TM induced considerle shift to lrger fruit (Figure 1). The incrementl increse in the yield of lrge fruit ws equivlent to 8 kg tree 1 (7.2 t h 1 ).The results for Spdon showed exctly the sme trend of high nd identicl yields in ll tretments (pprox. 6 kg tree 1 ), with significnt shift to the lrger fruit size (Figure 2). The mg l 1 GA 3 tretment hd etter fruit size distriution thn the control tretment, ut ws inferior to Bolero TM. In the fourth yer (4), we ssessed the effectiveness of pplying gierellin in smller doses throughout the lossom seson, insted of one ppliction t full loom (FB). GA 3 (ProGi ) ws pplied three-times, t dose of 3 mg l 1, throught the lossom period (t %, % nd % FB). Bolero TM ws pplied in two doses of.6% (4.3 mg l 1 GA 3 ) t 3% nd % FB, compred to single dose of.12% (8.6 mg l 1 GA 3 ) t FB.The totl mount of GA 3 in ll tretments ws pprox. 9 mg l 1. The yield of Spdon ws reltively low in the Jonthn orchrd, without significnt differences etween tretments (c. 3 kg tree 1 ), nd the fruits were therefore quite lrge. In spite of this, the size distriution etween tretments ws significntly different, with n ovious dvntge of the two Bolero TM tretments compred to the control nd ProGi (Tle II). No dvntge ws pprent from splitting the Bolero TM tretment into two pplictions. In the Rosh-Pin orchrd, where the yield ws somewht higher thn t Jonthn (c. kg tree 1 ; Figure 3), oth Bolero TM tretments were more oviously effective, producing pprox. doule the quntity of lrge fruit (3 kg tree 1 ) compred to 17 kg tree 1 for the control. It ws gin pprent tht gierellin lone contriuted very little, if t ll, to the increse in fruit size. In the semi-commercil tril conducted in different prt of the sme orchrd, considerle increse in yield ws otined in the treted locks (from 4 to 4 t h 1 ), due to the highly significnt increse of 14 t h 1 in the mount of fruit lrger thn 6 mm in dimeter. In, fter 4 yers of effective trils with Bolero TM, which confirmed tht fruit enlrgement ws due to cell elongtion, we exmined the effect of comintion of GA 3 with the cytokinin enzyldenine (BA; Bongrow TM ) tht enhnces cell division (Stern nd Flishmn, 3), to see if ny further increse in fruit size could e chieved. The comined tretment ws compred with Fruit size distriution (kg tree 1 ) 3 Smll (< ) Medium ( ) Lrge (> ) Fruit dimeter (mm) Bolero.12% (v/v) FIG.1 Effect of Bolero TM on fruit size distriution in Cosci per. PGR tretment ws pplied t full-loom. Dt re the mens of eight trees per tretment. The experiment ws conducted in the Jonthn orchrd in 3. Different lower-cse letters on the rs denote significnt differences etween the mens within ech size group, ccording to Duncn s new multiple rnge test, P =.. Bolero TM.12% (v/v) = 8.6 mg l -1 GA 3 + 6 mg l 1 2,4-D + 6 mg l 1 NAA. Fruit size distriution (kg tree 1 ) 3 4 6 6 7 7 Fruit dimeter (mm) Bolero.12% (v/v) ProGi.3% (v/v) FIG.2 Effects of ProGi nd Bolero TM on fruit size distriution in Spdon per. Tretments were pplied t full-loom. The experiment ws conducted in the Zrit orchrd in 3. Different lower-cse letters on the rs denote significnt differences etween the mens within ech size group ccording to Duncn s new multiple rnge test, P =.. ProGi.3% (v/v) = mg l 1 GA 3 ; Bolero TM.12% (v/v) = 8.6 mg l 1 GA 3 + 6 mg l 1 2,4-D + 6 mg l 1 NAA. c
86 Incresing per fruit size TABLE II Effects of three pplictions of ProGi, or one, or two pplictions of Bolero TM on fruit size nd yield of Spdon per, t the Jonthn orchrd in 4 Fruit size distriution (%) Totl yield Smll Medium Lrge Tretment [% (v/v)] (kg tree -1 ) (< mm) ( 6 mm) (> 6 mm) 3 33.4 31.4 3.2 ProGi.1% ( 3) 29 39.8 3.6 29.6 Bolero TM.12% ( 1) 33 22.1 28.3 49.6 Bolero TM.6% ( 2) 3 21.9 27.8.3 Men vlues within column followed y different lower-cse letter differ significntly ccording to Duncn s new multiple rnge test, P =.. ProGi.1% (v/v) = 3. mg l 1 GA 3 (t % + % + % FB). Bolero TM.12% (v/v) = 8.6 mg l -1 GA 3 + 6 mg l -1 2,4-D + 6 mg l -1 NAA (t FB). Bolero TM.6% (v/v) = 4.3 mg l -1 GA 3 + 3 mg l -1 2,4-D + 3 mg l -1 NAA (t 3% + % FB). TABLE III Effects of three pplictions of ProGi, or one, or two pplictions of Bolero TM on the fruit length:dimeter (L/D) rtio, seed numer per fruit, nd the percentge of fruit with deformed clyx t the Jonthn orchrd in 4 Deformed Tretment L/D rtio Seed/fruit (no.) clyx (%) 1.4. 6 ProGi.1% ( 3) 1.4 4.2 41 Bolero TM.12% ( 1) 1.48 4.6 Bolero TM.6% ( 2) 1. 4.8 8 Men vlues within column followed y different lower-cse letter differ significntly ccording to Duncn s new multiple rnge test, P =.. ProGi.1% (v/v) = 3. mg l 1 GA 3 (t % + % + % FB). Bolero TM.12% (v/v) = 8.6 mg l 1 GA 3 + 6 mg l 1 2,4-D + 6 mg l 1 NAA (t FB). Bolero TM.6% (v/v) = 4.3 mg l 1 GA 3 + 3 mg l 1 2,4-D + 3 mg l 1 NAA (t 3% + % FB). ech of the components lone, pplied s recommended commercilly [i.e.,.12% (v/v) Bolero TM t FB nd mg l 1 Bongrow TM pplied 14 d fter FB]. An dditionl tretment exmined the comintion of BA nd GA 4+7 t the sme time (14 d fter FB) s Perln TM. The orchrd produced high yield (6 kg tree 1 ) without differences etween tretments, ut the tretment effect ws ovious in the size distriution (Figure 4). GA 3 nd BA lone douled or tripled the yield of lrge fruit, ut their comintion [.12% (v/v) Bolero TM t FB plus mg l 1 Bongrow TM t FB + 14 d] hd no dditionl effect. However, ppliction of Perln TM, which comines BA nd GA 4+7 t FB + 14 d, resulted in four-fold increse in lrge fruit (from kg tree 1 in the control, to kg tree 1 for treted trees), mounting to n dditionl > t h 1. It is not yet cler whether this is the result of the simultneous ppliction of oth regultors, or the comintion of BA with different gierellin. A similr result ws reported recently for the Asin per Kosui, following comined tretment with the synthetic cytokinin CPPU 1 week fter FB, then with GA 3 1 month Fruit size distriution (kg tree 1 ) 4 3 3 Bolero.12% (v/v) Bolero.6% (v/v) 2 ProGi.3% (v/v) 2 Smll (< ) Medium ( 6) Lrge (> 6) Fruit dimeter (mm) FIG. 3 Effects of three pplictions of ProGi, or one, or two pplictions of Bolero TM on fruit size distriution in Spdon per. The experiment ws conducted t the Rosh-Pin orchrd in 4. Different lower-cse letters on the rs denote significnt differences etween the mens within ech size group ccording to Duncn s new multiple rnge test, P =.. ProGi.1% (v/v) 3 = three pplictions of 3 mg l 1 GA 3 ; Bolero TM.12% (v/v) = one ppliction of 8.6 mg l 1 GA 3 + 6 mg l 1 2,4-D + 6 mg l 1 NAA; Bolero TM.6% (v/v) 2 = two pplictions of 4.3 mg l 1 GA 3 + 3 mg l 1 2,4-D + 3 mg l 1 NAA. fter FB (Koyshi et l., 6). It ppers tht this result ws otined due to enhnced cell division (CPPU), followed y cell enlrgement (GA 3 ) t lter stge. As in this cse, GA 3 induced cell enlrgement, it is possile tht wht is importnt is simply the comintion of cytokinin nd gierellin, nd not necessrily GA 4+7. However, the timing of the pplictions cn lso hve n importnt role. Fruit shpe nd seed numer in Spdon One ppliction of Bolero TM t.12% (v/v) or two t.6% (v/v) incresed fruit size in Spdon without ny mlformtion (Tle III). The L:D rtio of fruit from oth tretments nd the control were the sme (1.4), nd the percentge of mlformed nd symmetricl fruit were lso the sme (pprox. %). However, with GA 3 lone (ProGi ), higher percentge of the fruit (41%) hd n norml clyx. No significnt vrition in seed numer could e discerned etween tretments, with n Yield of lrge fruit (kg tree 1 ) c c Bolero Bolero Bongrow Perln Perln.12%.12%.1%.1%.% + Bongrow (v/v) (v/v) (v/v) (v/v).1% (v/v) FIG.4 Effects of Bolero TM, Bongro TM, Bolero TM plus Bongro TM, or Perln on the yield of lrge (> 6 mm) Spdon fruit. The experiment ws conducted t the Jonthn orchrd in. Different lower-cse letters on the rs denote significnt differences etween the mens ccording to Duncn s new multiple rnge test, P =.. Bolero TM.12% (v/v) = 8.6 mg l 1 GA 3 + 6 mg l 1 2,4-D + 6 mg l 1 NAA t FB; Bongro TM.1% (v/v) = mg l -1 BA t FB + 14 d. The comintion tretment of Bolero TM nd Bongro TM ws Bolero TM pplied s noted ove plus Bongro TM pplied s noted ove. Perln.% (v/v) = mg l 1 BA + mg l 1 GA 4+7 t FB + 14 d. Perln.1% (v/v) = mg l 1 BA + mg l 1 GA 4+7 t FB + 14 d.
R. A. STERN,I.DORON nd R. BEN-ARIE 87 verge of 4.8 seeds per fruit (lthough control fruit hd slightly higher numer of seeds). CONCLUSION Commercil ppliction of GA 3 t FB to enhnce fruit set on Spdon nd Cosci per trees is prone to induce fruit mlformtion, due to symmetric enlrgement of cells t the lossom-end of the fruit. Addition of the uxins 2,4-D nd NAA (s in Bolero TM ) eliminted this prolem, nd lso noticely incresed fruit size in oth cultivrs, when it ws pplied t.12% (v/v) t FB. A split ppliction of two.6% (v/v) sprys t 3% nd % FB did not hve ny dditionl effect. GA 3 lone hs no effect on fruit size. A comintion of the cytokinin BA (tht increses cell division) nd the gierellin GA 4+7 (tht ffects cell elongtion) ech t mg l 1 (Perln TM ), pplied 14 d fter FB, gretly incresed fruit size without cusing ny deformtions. This work ws supported y Grnt from the Isreli Ministry of Agriculture nd Rurl Development nd y the JCA Chritle Foundtion. 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