Effects of Auxins Sprays on Yield, Fruit Size, Fruit Splitting and the Incidence of Creasing of Nova Mandarin

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1 Effects of Auxins Sprys on Yield, Fruit Size, Fruit Splitting nd the Incidence of Cresing of Nov Mndrin J. Greenerg nd I. Kpln M. Finzck, Y. Egozi nd B. Gildi Ministry of Agriculture, Mehdrin-Prior, Power center 1, Extension Service, P. O. Box 28, Beerot Yizhk 60905, Isrel Bet Dgn 50250, Isrel Keywords: Citrus, fruit thinning, 2,4-D, NAA, 3,5,6-TPA strct Effects of the plnt growth regultors (PGRs) 2,4-dichlorophenoxycetic cid (2,4-D, 40 mg L -1 ), nphthlenecetic cid (NAA, 300 mg L -1 ) nd 3,5,6-trichloro-2- piridil oxycetic cid (3,5,6-TPA, 15 mg L -1 ) on yield, fruit size, fruit qulity, fruit splitting nd the incidence of cresing of Nov mndrin were studied. All PGRs solutions were tnk-mixed with Bonus-npK fertilizer ( 5%). Sprys were pplied to whole trees t 2 dtes: erly spry t 13- mm fruitlet dimeter nd lte spry- t 26- mm fruitlet dimeter. Most fruit splitting occurred etween the eginning of Octoer nd the eginning of Novemer nd the totl fruit drop in the unspryed controls, cused minly y splitting, ccumulted to 150 fruit/tree (35% of the fruit). Erly spry of 2,4-D decresed fruit splitting to 25%, incresed yield to 50 kg/tree compred to 37 kg/tree in the controls, incresed fruit size nd hd no effect on the incidence of cresing. Erly NAA spry, thinned fruitlets, incresed fruit size, decresed splitting to 30%, decresed the incidence of cresing to 28%, compred to 36% in the controls, nd hd no effect on the yield. Lte NAA spry did not thin fruit nd hd no effect on fruit size ut the numer of fruit hrvested nd yield ws incresed to 52 kg/tree due to split fruit drop reduction to 21%, nd the incidence of cresing ws reduced to only 10% of the fruit. Erly 3,5,6-TPA spry cused strong fruitlets drop nd only 44 fruit/tree were hrvested. Lte 3,5,6-TPA spry did not thin fruit, hd no effect on fruit size, reduced the incidence of cresing to 22% nd reduced fruit splitting to 17%, cusing increse of the yield to 52 kg/tree. These dt suggest tht sprys of uxins on fruitlets, t time when they do not ffect fruit size nd do not thin fruitlets nymore, re effective for reducing fruit splitting nd the incidence of cresing of 'Nov' mndrin..

2 2 INRRODUCTION Nov mndrin fruit in Isrel suffer from two disorders: fruit splitting nd rind fruit cresing. Fruit splitting cuses fruit scission nd loss of up to 50% of the yield. Fruit splitting in 'Nov' hs een found negtively correlted with peel thickness nd puncturing resistnce of the fruit (Almel et l., 1994). In tht experiment in Spin the est reduction of splitting hs een otined y two sprys with mixture of GA3 nd 2,4-D, 30 nd 60 dys efore the nticipted onset of the disorder. Also clcium nitrte sprys reduced the disorder ut the sprys were ineffective in orchrds with low nturl incidence of splitting (Almel et l., 1994). In nother experiment in Nov in Spin Grci et l., (2001) showed tht two consequent sprys of 2,4-D ( 20 mg L -1 ), the first on full loom nd the second t petl fll, reduced fruit set nd reduced the percentge of splitting, while GA3 ( 20 mg L -1 ) sprys t the sme dtes incresed fruit set nd hd no effect on the percentge of splitting. Sprying Nov trees in Isrel with GA3 or 2,4-D in July, efore the onset of splitting, filed to reduce the disorder ( Goren et l., 1992). Fruit splitting in Nov orchrds in Isrel ws reduced slightly y successive sprys with potssium nitrte, nd etter effect ws otined when 2,4-D ws comined with this fertilizer ( Lvon et l., 1992). Nov suffers lso from fruit rind cresing, tht is serious disorder in some citrus vrieties. The disorder my e reduced y GA3 sprys in lte summer or utumn in Vlenci ornges (Monselise et l., 1976 ) nd Minneol tngelo (Greenerg et l., 1992 ). In lter experiments it hs een found tht NAA sprys on smll fruitlets re efficient for cresing reduction of Vlenci ornges (Greenerg et l., 1996 ) nd Newhll nvel ornges( Greenerg et l., 2000). In the present study the effects of sprys, on two ppliction dtes, with 2,4-D, NAA nd 3,5,6-TPA (ll comined with 'Bonus npk' fertilizer) on fruit splitting nd the incidence of cresing were exmined on Nov mndrin. Effects of the PGRs on yield fruit size nd qulity were lso ssessed.

3 3 MATERIALS AND METHODS The experiment ws conducted in 12 yer old commercil plnttion of Nov mndrin grfted on sour ornge ( Citrus urntium) rootstock. Treted trees were rrnged in rndomized lock design with four replictions of three trees ech. The dimeter of 100 rndomly selected fruitlets ws mesured t their equtor t the time of tretment nd the verge fruit dimeter ws clculted. Trees were spryed y hndgun, s single spry of 10 L/tree, with 2,4-D (40 mg L -1 ), NAA (300 mg L -1 ) nd 3,5,6-TPA (15 mg L -1 ) t two dtes: 29 My, 2002 when verge fruitlet dimeter ws 13 mm or t 2 July, 2002 when verge fruitlet dimeter ws 26 mm. The numer of split fruit per tree were counted nd removed periodiclly. Cresing incidence ws determined on 100 rndomly selected fruit on 2 dtes : 8 Decemer, 2002 nd t hrvest on 24 Decemer, At hrvest yield ws weighed from ech repliction seprtely. Rndomly selected fruit, 100 per repliction, were weighed nd their size t their equtor ws mesured. The verge fruit weight nd fruit size distriution were clculted -grding fruit into three sizes (lrge fruit 70 mm, medium fruit = mm nd smll fruit 60 mm). The verge numer of fruit per tree ws clculted y dividing the yield/tree y the verge fruit weight. The PGRs used were: NAA (The commercil preprtion Alphnol-super contins 200 g/l nphthlenecetic cid, Tpzol, Isrel), 3,5,6-TPA (The commercil preprtion Tops contins 33 g/l 3,5,6-trichloro-2-piridil oxycetic cid, Chimc Agriphr S.A. Belgium nd Tpzol, Isrel), nd 2,4-D (the commercil preprtion Hdrnol contins 500 g/l 2,4-dichlorophenoxycetic cid Mchteshim, Isrel). All PGRs solutions were comined with Bonus-npK fertilizer (5%), n improved spry formultion of potssium nitrte (contins 13% N, 2% P2O nd 44% K2O), Hif Agrologicl Power Isrel. Sttisticl nlysis of the results ws done using Duncn s multiple rnge test t 0.05 level. Percentges were nlyzed fter rcsin trnsformtion.

4 4 RESULTS Effects of the tretments (with pproximtely the sme finl totl fruit numer) on fruit drop (cused minly ecuse of fruit splitting) is shown in Fig.1. The PGRs sprys reduced fruit drop with preference to the lte TPA spry. Fig. 2 shows the effects of the PGRs on fruit numer per tree (dropped + hrvested fruit). NAA spryed t the erly dte thinned fruit, while, when pplied on lrger fruitlets it hd no ny thinning. Erly 3,5,6-TPA spry cused strong fruitlets drop nd only 44 fruit/tree were hrvested compred to 277 fruit/tree in the controls. Lte 3,5,6-TPA spry did not thin fruit. The effects of the tretments on splitting, expressed s percentges from totl fruit numer, is shown in Tle 1.The gretest splitting reduction ws otin y lte NAA nd lte TPA sprys: 21% nd 17% of splitting, respectively, compred to 35% in the controls. The tretments tht reduced fruit splitting incresed totl yield (Fig. 3). Erly 2,4-D nd NAA sprys incresed fruit size. Erly NAA thinned friutlets nd decresed totl yield, while the lte NAA spry hd not ny thinning effect nd hd no effect on fruit size ( Fig. 3). Effects of the tretments on the incidence of cresing on two evlution dtes re presented in Tle 1. The est effects on cresing reduction were otined y lte 3,5,6-TPA nd lte NAA sprys, with dvntge to NAA tht reduced the incidence of cresing, t the first dte of evlution, to 10% compred to 35% of cresing in the controls. The good tretments incresed significntly the quntity of fruit without cresing, tht is suitle for export, with dvntge to the lte NAA spry which incresed the quntity of fruit without cresing to 41 kg/tree compred to only 22 kg/tree in the controls (Fig. 4). DISCUSSION Synthetic uxin sprysfor incresing fruit size is common culturl prctice mong citrus growers in the world nd their effects hve een recently reviewed (Re., 2000 ). Comintion of the fertilizer potssium nitrte with the uxins

5 5 improves the effect (Erner et l., 1993 ). In the present study the uxin solutions were comined with the improved potssium nitrte spry fertilizer- 'Bonus npk', tht hs een found more effective thn potssium nitrte in 'Shmouti' ornge. (Greenerg et l., 2002 ) nd ws more effective lso in the present experiment ( dt not shown). 2,4-D nd NAA re pplied in Isrel for incresing fruit size of some citrus vrieties (Greenerg et l., 1996; Greenerg et l., 2000). Results of the present experiment show tht when these PGRs were spryed on smll 'Nov' fruitlets ( 13 mm verge dimeter), fruit size ws incresed (Fig. 3). Erly NAA spry thinned fruitlets nd decresed yield, ut NAA spry on lrger fruitlets, hd no thinning effect ( Fig 2). Similr effects of time of NAA ppliction hve een found in Newhll nvel ornge ( Greenerg et l., 2000). Erly 3,5,6- TPA spry hd very strong thinning effect which cused drop of most of the fruitlets, while lte spry didn t thin fruitlets ( Fig. 2). The min purpose of this study ws to find tretments tht my reduce the dmges cused to the Nov growers y fruit splitting nd cresing. Erly 2,4-D spry decresed fruit splitting (Figs 1, nd. 2), s hs een found y Lvon et l. (1992), ut it did not reduce the incidence of cresing (Tle 1). NAA spry decresed significntly the incidence of cresing of 'Nov' with etter effect to the lte ppliction ( Tle 1). Significnt reduction of the incidence of cresing y erly NAA ppliction hs een found lso in Vlenci ornge ( Greenerg et l., 1996 ) nd Newhll nvel ornge (Greenerg et l., 2000). Lte 3,5,6- TPA spry hd the est effect on fruit splitting reduction ( Figs 1, nd 2) nd reduced significntly the incidence of cresing (Tle 1). In the present experiment, 3,5,6- TPA cused lso up to 5% decrese in the juice content of the fruit ( sttisticl not significnt, dt not shown), fct tht hs to e considered when considering its use in orchrds with low percentge of juice. However, effect on the percentge of juice inconsistent nd desires dditionl study. CONCLUSIONS Auxins sprys on smll fruitlets increse the growers' returns from 'Nov' mndrin. When fruit thinning nd increse of fruit size is desired there is dvntge to erly NAA spry.

6 6 Lter sprys with the uxins NAA nd 3,5,6-TPA, t time when they do not thin fruitlets ny more nd do not ffect fruit size, re effective for reducing fruit splitting nd reducing the incidence of fruit cresing. Literture cited Almel, V., S. Zrgoz, E. Primo-Millo nd M. Agusti Hormonl control of splitting in Nov mndrin fruit. Jour. Hort. Sci. 69 (6): Erner, Y., Y. Kpln, A. Brch nd M. Hmon Incresing fruit size using uxins nd potssium. Act Hort.329: Grci-Luis, A.,A. M. M. Durte, M. Knduser, nd J. L. Gurdiol The ntomy of the fruit in reltion to the propensity of citrus species to split. Sci. Hort.87: Goren, R., M. Huermn nd J. Riov Effects of gierellin nd girdling on the yield of Nov (Clementine x Orlndo tngelo) nd Niv ( Vlenci x Wilking ) Proc. Int. Soc. Citriculture Greenerg, J., Y.Oren, G. Eshel nd E.E.Goldshmidt Gierellin A3 (GA3) on Minneol tngelo: Extension of the hrvest seson nd improvement of fruit qulity. Proc. VII Int. Soc. Citriculture Vol. 1: Greenerg, J., G. Eshel nd A. Gotfreed Effects of NAA, 2,4-D nd 2,4-DP on yield, fruit size nd cresing of Vlenci ornges. Proc.VIII Int. Soc. Citriculture Vol 2: Greenerg, J., I. Mossk nd I. Kpln Effects of NAA nd 2,4-DP on fruit size, yield nd cresing of Newhll nd Crter nvel ornges. Proc. Int. Soc. Citricult. IX Congress Greenerg, J., I. Kpln, M. Finzck, Y. Egozi, M. Hsn, A. Hocherg nd R. Port Effects of 2,4-D, 2,4-DP nd 3,5,6-TPA comined with 'Bonus npk' fertilizer on 'Shmouti' ornge. Et Hdr 48: (in Herew). Lvon R., S. Shpchiski. E. Mohel nd N. Zur Nutritionl nd hormonl sprys decresed fruit splitting nd fruit cresing of Nov. Hsdeh 72: (in Herew). Monselise. S.P., M. Wieser, N. Shfir., R Goren nd E.E. Goldshmidt Cresing of ornge peel-physiology nd control. J. Hort. Sci. 51: Re, E Fruit thinning for enhnced fruit size: n overview of strtegies. Proc. Int. Soc. Citricult. IX Congress

7 7 Tle 1. Effects of the tretments on the percentge of splitting nd the percentge of cresing on 2 dtes of evlution. tretment u Split fruit (%) Incidence of cresing (%) Dec. 8 Dec. 24 Control 35 x Erly 2,4-D (40 mg L -1 ) z Erly NAA (300 mg L -1 ) z Lte NAA 21 c 10 c 19 ( 300 mg L -1 ) y Lte 3,5,6- TPA (15 mg L -1 ) y 17 c u Tretment solutions contined 'Bonus npk' (5%). z Erly spry- pplied on 29 My 2002, to fruitlets 13 mm in dimeter. y Lte spry- pplied on 7 July 2002, to fruitlets 26 mm in dimeter. x Men seprtion within columns y Duncn's multiple rnge test, P Percentges were nlyzed fter rcsin trnsformtion.

8 Cumultive drop ( fruit/tree) Control Erly 2,4-D Lte NAA Lte TPA c c 0 Sept. 17 Oct. 8 Oct. 29 Nov.13 Dec. 5 Fig. 1. Effects of 2,4-D (40 mg L -1 ), NAA ( 300 mg L -1 ) nd 3,5,6-TPA ( 15 mg L -1 ) sprys on the cumultive fruit drop ( minly due to splitting). Erly spry- pplied on 29 My 2002, to fruitlets 13 mm in dimeter. Lte spry- pplied on 7 July 2002, to fruitlets 26 mm in dimeter. Tretment solutions contined 'Bonus npk' (5%). Men seprtion on the 5 Dec. results, y Duncn's multiple rnge test, P 0.05.

9 No. fruit/tree Hrvested Split c Control Erly 2,4-D Erly NAA Lte NAA TREATMENT Erly TPA c d Lte TPA c Fig. 2.. Effects of 2,4-D (40 mg L -1 ), NAA ( 300 mg L -1 ) nd 3,5,6-TPA ( 15 mg L -1 ) sprys on fruit numer (split + hrvested fruit). ). Erly spry- pplied on 29 My 2002, to fruitlets 13 mm in dimeter. Lte spry- pplied on 7 July 2002, to fruitlets 26 mm in dimeter. Tretment solutions contined 'Bonus npk' (5%). Men seprtion mong split fruit nd hrvested fruit seprtely, y Duncn's multiple rnge test, P 0.05.

10 Yield (kg/tree) Smll Medium Lrge Control c Erly 2,4-D Erly NAA Lte NAA TREATMENT Erly TPA Lte TPA Fig 3. Effects of 2,4-D (40 mg L -1 ), NAA ( 300 mg L -1 ) nd 3,5,6-TPA ( 15 mg L -1 ) sprys on yield nd fruit size distriution. Erly spry-pplied on 29 My, 2002 to fruitlets 13 mm in dimeter. Lte spry- pplied on 7 July, 2002 to fruitlets 26 mm in dimeter. Tretment solutions contined 'Bonus npk' (5%). Men seprtion mong the totl nd the lrge fruit yield, y Duncn's multiple rnge test, P 0.05.

11 Yield (kg/tree) 00 Totl yield Without cresing Lte TPA Lte NAA Erly NAA Erly 2,4-D Control Fig. 4. Effects of 2,4-D (40 mg L -1 ), NAA ( 300 mg L -1 ) nd 3,5,6-TPA ( 15 mg L -1 ) sprys on the totl yield nd the yield without cresing t the lte hrvest dte (Dec. 24). Erly spry- pplied on 29 My 2002, to fruitlets 13 mm in dimeter. Lte spry- pplied on 7 July 2002, to fruitlets 26 mm in dimeter. Tretment solutions contined 'Bonus npk' (5%). Men seprtion ws done seprtely to the totl yield nd the yield without cresing, y Duncn's multiple rnge test P 0.05.