Research Article The Effect of Paclobutrazol Application Time and Variety on Growth, Yield, and Quality of Potato (Solanum tuberosum L.

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1 Advnes in Agriulture Volume 2016, Artile ID , 5 pges Reserh Artile The Effet of Ploutrzol Applition Time nd Vriety on Growth, Yield, nd Qulity of Potto (Solnum tuerosum L.) Ottili Mvongwe, 1 Brend T. Mnenji, 2 Munyrdzi Gwzne, 2 nd Mishek Chndiposh 2 1 Ministry of Agriulture, Mehniztion nd Irrigtion Development, No. 1 Borrowdle Rod, Ngungunyn Building, Hrre, Zimwe 2 Deprtment of Agronomy, Midlnds Stte University, Privte Bg Box 9055, Gweru, Zimwe Correspondene should e ddressed to Mishek Chndiposh; hndiposhm@msu..zw Reeived 2 Deemer 2015; Aepted 11 Jnury 2016 Ademi Editor: Tior Jnd Copyright 2016 Ottili Mvongwe et l. This is n open ess rtile distriuted under the Cretive Commons Attriution Liense, whih permits unrestrited use, distriution, nd reprodution in ny medium, provided the originl work is properly ited. An experiment ws set up to investigte the effet of time of ploutrzol pplition nd vriety on growth, yield, nd qulity ofpottoingreenhouset34 C(±3) nd 21 C(±3) dy nd night tempertures, respetively, with 60% reltive humidity. The experiment ws set up s 2 4 ftoril design in CRD with 3 replitions. The first ftor ws potto vriety nd the levels were BP1 nd Dimond. The seond ftor ws ploutrzol pplition time nd the levels were 28 (Dys After Plnting) DAP, 35 DAP, nd 42 DAP nd no ploutrzol pplied (ontrol). Erly pplition of ploutrzol redued stem length, numer of tuers per plnt, nd sugr ontent of potto; furthermore, it inresed strh ontent nd yield ompred to lte pplition nd no ploutrzol tretments. Erly pplition of ploutrzol t 28 DAP is reommended in high temperture zones s it inresed the yield y 108% nd qulity of potto. 1. Introdution Potto is ool seson rop nd the optimum temperture requirements for tuer development hve een reported to e in the rnge of C[1].Pottoprodutionhseen limited to ool regions in Zimwe nd yet the ountry hs more thn 43% of semirid re [2]. To inrese food nd nutrition seurity in the ountry, it is impertive to grow pottoes in high temperture regions. High tempertures use redution in the rte of photosynthesis, trnslotion of ssimiltes to tuers, nd onversion rte of surose into strh resulting in limited tuer formtion nd growth [3]. The yield redution t high tempertures is prtly due to redued ssimilte prtitioning nd delyed tuer initition [4]. At high tempertures, folige growth is vigorous nd onsiderle mounts of rohydrtes re utilized for folige growth t the expense of tueriztion [5]. The totl dry mtter prodution nd its distriution to the different plnt orgns is n importnt ftor ffeting tuer yield in potto [6]. The trnsition of stolon into tuer t high tempertures is limited s there is n inrese in the level of gierelli id in lef uds limiting tuer prodution [3]. High levels of gierelli id led to higher rohydrte llotion to shoots t the expense of tuers [5]. One of the ttempts to inrese potto produtivity in tropil limtes where high tempertures re experiened is the use of plnt growth regultors suh s ploutrzol [3]. The mode of tion of ploutrzol is the inhiition of gierelli id synthesis in plnts. The inhiition of gierellin prodution y ploutrzol results in slow ell division nd elongtion without using toxiity to ells [7]. Applition time of ploutrzol my ffet potto yield in high temperture res. Ploutrzol tretment of potto plnts promoted tueriztion in vitro nd under greenhouse onditions with ultivr response to the timing of tretment [8]. Tueriztion is ontinuous proess nd ll the different developmentl stges from stolon indution to tuer growth myourtoneplntutnotlltuerswilleleto

2 2 Advnes in Agriulture develop to usle tuers t hrvest time [9]. The ontinuous pperne of stolons during tuer ulking period my not ontriute to the numer of tuers hrvested s eh vriety hs time when stolon swelling eses [10] nd therefore timing of ploutrzol pplition is ritil. Applition of plnt growth regultors t tuer initition n lter photosyntheti prtitioning in fvour of tuer prodution nd inrese yields [7]. Celis-Gmo et l. [11] found out tht stolon formtion ourred 29 DAP nd thestolontipswellingstrtedfrom29to36dapforthe ultivrs tht were under study. Tuers tht overly ttin the gretest weight re usully produed y the lowest stolons nd re formed t the eginning of tuer development [10]. However, there is limited informtion on the pproprite time of ploutrzol pplition using our lol vrieties to mximise yield nd qulity of potto tuers under onditions of high tempertures. 2. Mterils nd Methods 2.1. Reserh Site nd Chrteristis. The reserh ws rried out t Hrre Reserh Sttion (31 03 End17 48 S). It is loted within groeologil region II with n ltitude of 1506 m ove se level. The reserh sttion reeives nnul rinfll of 820 mm. The experiment ws onduted in greenhouse nd the dy temperture ws 34 C(±3) nd thenighttemperturews21 C(±3). The verge reltive humidity in the greenhouse ws 60%. The experiment ws set up in April to July 2014 nd dy length ws hrterised y short dys nd long nights Experimentl Design nd Tretments. The experiment ws set up s 4 2 ftoril in omplete rndomized design with 3 replitions. The first ftor ws time of ploutrzol pplition nd the seond ftor ws vriety with the levels shown in Tle Plnt Culture. Two vrieties of potto seed Dimond nd BP1 were left to sprout in drk room until the sprouts were out 2 m in length. The sprouted seed tuers were then trnsferred to room with diffuse light to hrden sprouts for two weeks until the sprouts turned from white to green. The soils used for plnting were predominntly red lys. Plnting ws done in 20 L lk plsti pokets tht were 50 m 40m.Thepoketswereinitillyhlffilledwithsoil toheightof25m.bslfertilizerwsppliedtrte of 2000 kg/h Compound S (7 : 21 : 7) nd ws inorported into the pokets. Plnting holes tht were 10 m deep were duginehpoketnd1tuerwspledinehpoket, overed with soil, nd irrigted. One experimentl unit ws omprised of 5 pots. Top dressing ws done t four weeks fter emergene using Ammonium Nitrte (34.5% N) t rte of 200 kg/h. Erthingupwsdoneyfillingupthepoketswiththe sme soil tht ws used t plnting. Preventtive sprys for lights were done on weekly sis using opper oxyhloride. Weeding ws done y pulling the weeds y hnd from the pokets whilst they were still young. Wtering ws done when neessry depending on the stge of rop growth. Hrvesting of the tuers ws done fter 120 DAP. Tle 1: Tretment struture for the effet of time of ploutrzol pplition on growth, qulity, nd yield of potto. Tretment Vriety Time of ploutrzol pplition 1 BP BP BP BP1 No ploutrzol (ontrol) 5 Dimond 28 6 Dimond 35 7 Dimond 42 8 Dimond No ploutrzol (ontrol) Tretment Applition. Ploutrzol 29.9% tive ingredient ws pplied t rte of 250 g/h nd ws pplied t28,35,nd42dapordingtotretmentstrutureshown in Tle 1. A 15 litre knpsk spryer ws used for sprying to ttin full over spry Mesurements nd Dt Anlysis. Mesurements tken inluded stem dimeter t the se nd length on two rndomly smpled plnts per experimentl unit t 49 nd 63 DAP, numer of tuers per plnt, yield, strh ontent, reduing sugr ontent of potto tuers [12], nd grdes of potto t the end of the experiment (120 DAP). The grdes of potto were divided into smll ( mm), medium ( mm), lrge ( mm), nd extr lrge (>84 mm dimeter). Anlysis of vrine of dt ws done using Genstt Version 14. Tretment mens were seprted using the LSD t 5% level of signifine. 3. Results nd Disussion 3.1.EffetofTimeofPloutrzolApplitiononPottoStem Length (m) t 49 nd 63 DAP. Ploutrzol tretment t 28 DAP resulted in stems tht were shorter ompred to dely in pplition of the growth regultor nd no ploutrzol tretments t 49 nd 63 DAP (Tle 2). Proly erly pplition of ploutrzol quikly rrested the tivity of gierelliidinsideplntellswhihreresponsilefor stem elongtion, hene reduing the length of stems. Gierelli id is responsile for stem elongtion y inresing the internode length [13]. Ploutrzol redues the level of gierelli id inside plnt ells y interfering with the oxidtive steps of gierellin preursor ent-kuren to entkureni id loking the synthesis of gierellins in the erly step of its iosyntheti pthwy [14, 15]. These results re similr to findings y Bndr et l. [8] tht pplition ofploutrzolterlytuerinititionreduesthehulm growth signifintly ompred to when it is pplied t lte stolon initition. 3.2.EffetofTimeofPloutrzolApplitiononPotto Stem Dimeter (m) t 49 nd 63 DAP. Erly pplition

3 Advnes in Agriulture 3 Tle 2: Effet of time of ploutrzol pplition on potto stem length (m) t 49 nd 63 DAP. Time of ploutrzol Stem length (m) pplition (DAP) 49 DAP 63 DAP No ploutrzol d d P vlue <0.001 <0.001 LSD Mens with the sme letters in eh olumn re not sttistilly different t 5% signifine level. Tle 3: Effet of time of ploutrzol pplition on potto stem dimeter (m) t 49 nd 63 DAP. Time of ploutrzol Stem dimeter (m) pplition (DAP) 49 DAP 63 DAP No ploutrzol d d P vlue <0.001 <0.001 LSD Mens with the sme letters in eh olumn re not sttistilly different t 5% signifine level. of ploutrzol resulted in thiker nd more ompt stems thn lte pplition nd no ploutrzol tretments (Tle 3). Similrly, erly pplition of ploutrzol inresed the dimeter of stems onsiderly ompred to lte pplitions. This my e explined y the low levels of gierelli id fter erly pplition of ploutrzol s high levels of gierelli id limit rdil expnsion of plnt orgns [16]. Proly the redution in stem length due to erly pplition of ploutrzol ompred to lte pplition of ploutrzol my hve resulted in inreses in stem dimeter for the former ompred to the lter. Ploutrzol tretment inreses the thikness of ortex, vsulr undles, nd pith dimeter resulting in thiker stems [17] Effet of Time of Ploutrzol Applition on Totl Numer of Potto Tuers per Plnt. Signifint differenes (P < 0.05) in time of ploutrzol pplition were oserved with respet to totl numer of tuers per plnt. The lest numer of potto tuers ws reorded in plots where ploutrzol ws pplied t 28 DAP lthough it ws not signifintly different from 35 DAP (Figure 1). The redution in the numer of tuers per plnt my e ttriuted to derese in the numer of stolons due to low levels of gierelli id fter ploutrzol pplition. The fewer numers of stolons resulted in fewer numers of tuers s they re formed fter the differentition of stolons into vegettive storge orgns. These results gree with the findings y Vreugdenhil nd Sergeev [5] tht pplition of gierelli id redues numer of tuers per plnt. Totl numer of tuers/plnt DAP 35 DAP 42 DAP No ploutrzol Time of ploutrzol pplition Figure1:Effetoftimeofploutrzolpplitionontotlnumer of potto tuers per plnt. Yield (kg)/plnt DAP 35 DAP 42 DAP Time of ploutrzol pplition Figure2:Effetoftimeofploutrzolpplitiononpottotuer yield (kg) per plnt. d No ploutrzol 3.4. Effet of Time of Ploutrzol Applition on Potto Yield (kg/plnt). The highest potto yield ws oserved in tretments where ploutrzol ws pplied t 28 DAP. Yield of out 108% ws reorded in erly pplition when ompred to no ploutrzol tretments (Figure 2). The inrese in yield my hve een used y the redution of stem length tht ws oserved in the experiment s more ssimiltes were hnnelled to tuer growth inresing yield [6]. The inrese in yield in tretments where ploutrzol ws pplied erly my lso e explined y erly tueriztion due to low levels of gierelli id. Applition of ploutrzol oiniding with tuer initition resulted in more yields ompred to pplition of ploutrzol t lte tuer initition [8, 10]. 3.5.EffetofTimeofPloutrzolApplitiononPottoTuer Grdes per Plnt. Plnts treted with ploutrzol t 28 nd

4 4 Advnes in Agriulture Tle 4: Effet of time of ploutrzol pplition on potto tuer grdes s per plnt. Time of ploutrzol pplition in DAP Extr lrge Lrge Medium Smll No ploutrzol d d d P vlue <0.001 <0.001 <0.001 <0.001 LSD Mens with the sme letters in eh olumn re not sttistilly different t 5% signifine level. Strh ontent s % of totl sugrs DAP 35 DAP 42 DAP No ploutrzol Time of ploutrzol pplition Figure3:Effetoftimeofploutrzolpplitiononpottotuer strh ontent s % of sugrs. 35 DAP hd the iggest numer of extr lrge nd lrge tuers (Tle4).Theinreseinsizesoftuersmyesresult of low ompetition for ssimiltes sine the erly pplied ploutrzol plnts hd less numers of tuers s shown in Figure 1. These results my lso e explined y the redution in stem length for erly ploutrzol tretments nd hene more ssimiltes were prtitioned to tuer growth ompred to hulm growth resulting in inresed size of tuers. The inrese in potto size my lso e linked to erly tueriztion in plnts treted with ploutrzol t 28 nd 35 DAP [6]. 3.6.EffetofTimeofPloutrzolApplitiononPottoTuer Strh Content s % of Sugrs. Applition of ploutrzol 28 DAP resulted in 28% inrese in tuer strh ontent ompred with tretments where ploutrzol ws not pplied (Figure 3). The inrese in strh ontent with erly ploutrzolpplitionmighthveeenusedyhigher sink strength s evident on the inrese in tuer size indited y tuer grdes shown in Tle 4 enhning strh synthesis nd umultion due to low levels of gierelli id. High levels of gierelli id during tueriztion impede strh umultion nd hene low levels of strh in plnts where ploutrzol ws not pplied. The inrese in strh ontent d Reduing sugr s % gluose DAP 35 DAP 42 DAP No ploutrzol Time of ploutrzol pplition Figure 4: Effet of time of ploutrzol pplition on potto tuer reduing sugr ontent s % gluose. in erly pplied ploutrzol plnts my lso hve een used y erly tueriztion. Erly ploutrzol pplied plnts hd more time to ttrt ssimiltes resulting in inrese in strh ontent ompred to the lte pplition. Tretment of plnts with ploutrzol uses n inrese inthenumerofenzymesthtreresponsileforstrh iosynthesis suh s strh synthse, therefore inresing strh ontent in tuers [9]. Applition of ploutrzol results in inresed strh synthesis nd umultion in tuers [17] nd hene inresed strh ontent in ll plnts where ploutrzol ws pplied. The lest strh ontent ws reorded in tuers where ploutrzol ws not pplied nd this n e explined y high levels of gierellins tht impede strh umultion in tuers. 3.7.EffetofTimeofPloutrzolApplitiononPottoTuer Reduing Sugr Content s % Gluose. The levels of reduing sugrs were the lowest in plnts treted with ploutrzol t 28 DAP (Figure 4). The redution in reduing sugr ontent myhveeenusedyinreseinstrhontentinthis tretment implying tht most of the reduing sugrs were onverted to strh. This my e explined y low levels of gierelliidthtstimultesenzymessuhsstrhsynthse nd strh iosynthesis tht onvert sugrs to strh [9]. 4. Conlusions Erly pplition of ploutrzol t 28 DAP redued the stemlengthndinresedthestemdimetery40%nd74%, respetively. Erly pplition of ploutrzol redued the totl numer of tuers per plnt nd inresed potto tuer yield. Lte pplition of ploutrzol t 42 DAP inresed tuer reduing sugr ontent, redued the grdes of tuers, nd deresed tuer strh ontent. Conflit of Interests The uthors delre tht there is no onflit of interests regrding the pulition of this pper.

5 Advnes in Agriulture 5 Aknowledgments TheuthorslsownttothnkDr.D.Rukuniforhisssistneinomingupwiththeprojetproposl.Mnythnks re due to the Deprtment of Reserh nd Speilist Servies nd Ms. O Mvhngeni in prtiulr for lloting greenhouse spe to rry out the projet. Referenes [1] R. Shfleiter, M. Bonierle, nd D. Ty, Applying photosynthesis reserh to improvement of food rops, in Proeedings of the Interntionl Loster Aquulture Symposium (ACIAR 13), vol.140,pp.52 59,Medn,Indonesi,Novemer2013. [2] C. Gore, Y. Kterere, nd S. Moyo, The Cse for Sustinle Development in Zimwe Coneptul Prolems, Conflits nd Contrditions, ENDA-Zimwe nd ZERO, Hrre, Zimwe, [3] M. Rossnn, B. Mustf, nd L. Eny, The effetiveness of ploutrzol nd orgni fertilizer for the growth nd yield of pottoes in medium plin, Sientifi & Tehnology Reserh,vol.3,no.7,pp ,2014. [4] J. Vn Dm, P. L. Koomn, nd P. C. Struik, Effets of temperture nd photoperiod on erly growth nd finl numer of tuers in potto (Solnum tuerosum L.), Potto Reserh,vol. 39,no.1,pp.51 62,1996. [5] D. Vreugdenhil nd L. I. Sergeev, Gierellins nd tueriztion in potto, Potto Reserh, vol.42,no.3-4,pp , [6] V. Blmni nd B. W. Poovih, Retrdtion of shoot growth nd promotion of tuer growth of potto plnts y ploutrzol, Amerin Potto Journl,vol.62, no.7,pp , [7] S. Mnjul, S. Bndr, K. Tnino, nd D. R. Wterer, Effet of plntgrowthregultorsonseedtueryieldinpottoes, Journl of Plnt Growth Regultion,vol.34,pp.67 78,1999. [8] M.S.Bndr,K.K.Tnino,ndD.R.Wterer, Effetofpot size nd timing of plnt growth regultor tretments on growth nd tuer yield in greenhouse-grown Norlnd nd Russet Burnk pottoes, Journl of Plnt Growth Regultion, vol.17,no. 2, pp , [9] N. J. G. Appeldoorn, S. M. De Bruijn, E. A. M. Koot-Gronsveld, R. G. F. Visser, D. Vreugdenhil, nd L. H. W. Vn der Pls, Developmentl hnges of enzymes involved in onversion of surose to hexose-phosphte during erly tueristion of potto, Plnt,vol.202,no.2,pp ,1997. [10] D. Levy nd R. E. Veilleux, Adpttion of potto to high tempertures nd slinity review, Amerin Journl of Potto Reserh, vol. 84, no. 6, pp , [11] C. Celis-Gmo, P. C. Struik, E. Josen, nd R. G. F. Visser, Temporl dynmis of tuer formtion nd relted proesses in rossing popultion of potto (Solnum tuerosum), Annls of Applied Biology,vol.143,no.2,pp ,2003. [12] L. S. Munson nd P. H. Wlker, The unifition of reduing sugr methods, Journl of the Amerin Chemil Soiety, vol. 28, no. 6, pp , [13] T.D.Dvis,E.A.Curry,ndG.L.Steffens, Chemilregultion of vegettive growth, Critil Reviews in Plnt Sienes,vol.10, no. 2, pp , [14] P. Hedden nd J. E. Gree, Inhiition of gierellins iosynthesis y ploutrzol in ell-free homogentes of Curuit mxim endosperm nd Mlus pumil emryos, Plnt Growth Regultion,vol.4,no.1,pp ,1985. [15] J. Ltimer nd B. Whipker, Using Piolo with Hereous Perennils, edited y: Fine Ameri, [16] C.L.Wenzel,R.E.Willimson,ndG.O.Wsteneys, Gierellin-indued hnges in growth nisotropy preede gierellindependent hnges in ortil mirotuule orienttion in developing epiderml ells of rley leves. Kinemti nd ytologil studies on gierellin-responsive dwrf mutnt, M489, Plnt Physiology,vol.124,no.2,pp ,2000. [17] T. Tsegw, S. Hmmes, nd J. Roertse, Ploutrzol-indued lef, stem, nd root ntomil modifitions in potto, Hort- Siene, vol. 40, no. 5, pp , 2005.

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