Avilble online t www.pelgireserchlibrry.com Europen Journl of Experimentl Biology, 2014, 4(4):98-102 ISSN: 2248 9215 CODEN (USA): EJEBAU Effects of chemicl tretments on dormncy breking nd some sprouting chrcteristics of two potto cultivrs in different tuber sizes Frshid Hssni*, Abbs Zrein nd Enyt Rezvni Seed nd Plnt Certifiction nd Registrtion Reserch Institute (SPCRI), Irn -------------------------------------------------------------------------------------------------------------------------------------------- ABSTRACT Seed potto dormncy hs been considered in breeding progrms, virus-free seed producing nd wre potto production. Seed dormncy is different between potto cultivrs. Dormncy in potto mini-tuber buds is one of the limiting fctors on plnting them fter hrvesting. This study ws undertken in fctoril bsed on complete rndomized design with rrngement three replictions to investigting the effect chemicl tretments, cultivrs nd seed size on seed dormncy breking of potto in 2011-2012 t Seed nd Plnt Certifiction nd Registrtion Institute. The results showed tht the chemicl mterils ws significnt t (p<0.01) on number of dys to sprouting, number of dys to dormncy breking nd the totl number of sprouting. Number of sprouting per tuber nd number of dys to sprouting nd dormncy breking between two cultivrs were different. Utiliztion of Gibberellic cid reduced the sprouting time from 25 to 13 dys. The lowest number of dys to dormncy breking in verge of 28.8 dys ws obtined in pplying GA3 on 20-25 mm mini-tuber. Thio-ure ppliction hd the most effect on decresing the dys to emergence in verge of 25.1dys nd lso incresed number of sprout from 1.41 to 2.03. The result of this project showed tht with incresing the mini-tuber size, the dys to dormncy breking decresed nd lso the number of sprout. Therefore ppliction of GA3 is dvisble for decresing dys to sprouting, ccelerting sprout length nd consequently resulted in breking mini-tuber dormncy of potto for short time. Keywords: Dormncy breking, Mini-tuber, Gibberellic cid, Thio-ure,Crbon di-sulphid. INTRODUCTION Potto (Solnum tuberosum L.) is considered s n importnt nd strtegic product, hving the second rnk in terms of production nd third one ccording to its importnce mong other produced foods in Irn [2]. One of the most populr wys to produce pre-bsic seed of potto (Solnum tuberosum L.) is to grow mini-tubers in the greenhouse from in vitro plntlets produced from nodl cuttings. Mini-tuber production hs found its plce in the seed production systems ll over the world s it cretes bridge between the in vitro rpid multipliction bsed on nodl cuttings nd the field multipliction of seed tubers. Mini-tubers re more flexible, cn be stored nd mechniclly plnted, nd show lrger vigour thn either microtubers or in vitro plntlets [17]. Lck of good qulity seed mong growers is mjor problem dversely ffect the expnsion of potto production in mny developing countries[5]. One mjor problem fcing production of qulity potto seed is poor sprouting, due to dormncy, which led to delyed plnting nd poor crop emergence nd vigor [18]. After hrvest, norml seed tubers show dormncy for bout 1 15 weeks, depending on cultivr, tuber size, conditions before hrvest nd storge conditions. Smll tubers, such s mini-tubers, even hve longer periods of dormncy [12] nd re more sensitive to dverse conditions during storge [17] In Irn, lrge mount of mini-tubers is hrvested between Mrch nd April. Norml plnting time of these mini-tubers in the field or in the greenhouse is in the month of My or beginning of June. So there is not enough time between hrvest nd plnting to brek dormncy nturlly. This 98
Frshid Hssni et l Euro. J. Exp. Bio., 2014, 4(4):98-102 clls for re lible technique to brek the dormncy of these smll tubers chemiclly. Use of low quntities of growth promotes like thioure, rindite, crbon disulphide nd bromo-ethne [3] nd gibberellic cid [4,6] to promote potto seed sprouting hs been suggested.this study under tken to evlute the effect of growth promotes nd size on dormncy breking of mini-tubers of potto. MATERIALS AND METHODS This study ws done in the greenhouse of SPCR Institute (Seed nd Plnt Certifiction nd Registrtion reserch Institute) in Krj, Irn. This reserch crried out in form of fctoril bsed on rndomized complete design in three replictions. Experimentl fctors were considered chemicls s the first fctor in four levels (control, 50 g/lit gibberellic cid, 25 ml/m 3 crbon disulfide, 3% thio-ure), potto cultivrs s the second fctor in two levels (Agri nd Burren) nd potto mini-tuber size s the third one in four levels (12-20 millimeter, 20-25 millimeter, 25-30 millimeter nd 30-35 millimeter). 2.1. In Vitro Seedlings Production Virus-free seedlings were produced using combintion method of het tretment nd meristem isolted nd cultured in MS liquid medium onto pper bridges nd then trnsferred cultures in suitble growth condition in the growth chmber. Obtined seedlings using single-node cuttings on solidified MS medium multiply with gr nd were trnsmitted to growth chmber with temperture of 24 degrees Celsius, light for 16 hours nd light intensity of 4500 lux nd were kept there bout 4 weeks to grow nd become the new seedlings 2.2.Mini-tuber Production in Greenhouse After obtining the required number of seedlings from ech cultivr, seedlings 25-30-dy lifetime hving 7 to 9 leves were selected for trnsfer to greenhouse. In the greenhouse, seedlings were brought out of the pots nd the roots were wshed with wter to remove medium residul mtter. Clened seedlings trnsferred crefully into the bed including mixture of soil disinfected by fungicides nd insecticides nd perlite nd pet moss in the rtio of 1: 2: 1 nd for few dys plstic cp ws plced on them to dpting seedlings with greenhouse environment nd preventing dmge to seedlings. Seedlings were growth in growth chmber with dy nd night tempertures of 18 nd 12 Celsius respectively, 12 hours dy length nd 85% reltive humidity. After pssing bout 100 dys, the mini-tubers were hrvested nd trnsferred to lbortory for sprouting. After selecting mini-tubers but prior the pplying chemicls nd growth-stimulting hormone mini-tubers were wshed with wter nd plced in try. 2.3.Gibberellic cid Tretment Smple contining 240 mini-tuber of ech cultivr were immersed for three hours by 50 ppm gibberellic cid tretment solution in groups (12-20 millimeter, 20-25 millimeter, 25-30 millimeter nd 30-35 millimeter) nd then smples were plced into plstic try with room temperture for germintion. 2.4.Thio-ure Tretment Smple contining 240 mini-tuber of ech cultivr were immersed by thio-ure 3% solution for one hour in groups (12-20 millimeter, 20-25 millimeter, 25-30 millimeter nd 30-35 millimeter) nd then smples were plced into plstic try in grner with 90 reltive humidity, bsolute drkness nd temperture of 18 C for germintion. 60 micro-tubers from ech cultivr ws plced immeditely fter hrvest nd wshing with distilled wter in stndrd storge conditions s control tretment without the ppliction of hormones nd chemicls. The time intervl between the pplictions of chemicls till to sprout emergence in micro-tubers ws recorded. Emersion of sprout bout 2 mm from tubers is n pproprite criterion for dormncy period ending nd whenever 80 percent of minitubers show tht symptoms it consider s dormncy brek time. During the experiment, tubers hving sprout were counted nd were seprted every 10 dys. Averge of 2 mm sprouts of ech micro-tuber ws recorded one week fter the end of dormncy. 2.5.Crbon Di-sulfide Tretment For the crbon disulphide tretment, 240 mini-tubers were put in 15 19 32 cm plstic continers with tightly fitting lids t room temperture for 72 h. Sufficient CS2 ws supplied in liquid form in 25 ml bekers to give the required concentrtion in the continer volume. 60 micro-tubers from ech cultivr ws plced immeditely fter hrvest nd wshing with distilled wter in stndrd storge conditions s control tretment without the ppliction of hormones nd chemicls. The time intervl between the pplictions of chemicls till to sprout emergence in micro-tubers ws recorded. Emersion of sprout bout 2 mm from tubers is n pproprite criterion for dormncy period ending nd whenever 80 percent of mini-tubers show tht symptoms it consider s dormncy brek time. During the experiment, tubers 99
Frshid Hssni et l Euro. J. Exp. Bio., 2014, 4(4):98-102 hving sprout were counted nd were seprted every 10 dys. Averge of 2 mm sprouts of ech micro-tuber ws recorded one week fter the end of dormncy. 2.6.Sttisticl Anlysis To nlyze this study s obtined dt pplied ANOVA nlysis procedure of SAS softwre. For downing the men comprisons LSD test ws used by probbility level of 5%. RESULTS AND DISCUSSION 3.1.Dys to Sprouting According to Tble 1 results of nlysis of vrince lbortory trits shows tht ll of experimentl fctors min nd interction effects ws significnt (P<0/01) on dys to sprout emergence. But triprtite effect did not the sme significnt differences. The highest dys to sprouting were observed by verge of 25.2 dys in control nd the lowest dys obtined in gibberellic cid tretment by verge of 13.9 dys. Bsed on chieved results ppliction of ll three growth regultors hormones used in this experiment, reduces the number of dys until the ppernce of the sprout. It seems tht ppliction of growth regultors nd gibberellic cid most of ll, cuses to postponement of sprouting which is in consistent by Helsinki et l,[9] nd Gomez nd Mrtinez [8] results. It is worth noting tht the number of dys to sprouting showed different results in two vrieties tht could be stted due to different physiologicl chrcteristics of different vrieties. It ws lso observed tht the number of dys to sprouting, depending on seed size showed different results. So tht just 30 to 35 mm with n verge of 17.8 dys significntly ffected the number of dys to sprouting compre to the other sizes. Results of Khorshidi nd Hssnpnh [11] lso showed tht incresing the seed size increses monotoniclly on the size of the sprout, but it cn be linked to the most vigorous seeds of lrger seed for creting bigger sprouts. 3.2.Totl number of sprouting The results (Tble 1) showed tht the ppliction of growth regultors nd seed tubers vrieties nd different sizes ws ble to hve significnt effect on the totl number of sprouting. The results of this experiment cn be stted tht the use of chemicls used in these experiments ws incresed totl number of sprouting of potto. In this study, compre to control chemicls tretments incresed totl number of sprouting, tht mong the ll, highest rtes in sprout length belongs to the ppliction of Thio-ure. The results of these experiments is consistent with the results of the Rehmn et l,[13]. It should be noted tht the totl number of sprouting in Burren cultivr 1.92 ws higher thn the Agri cultivr (tble 2). These differences cn occur due to vrious physiologicl hbits. Also difference in seed size s well cuses difference in number of the sprout. So tht the number of sprout incresed whtever s well s seed tuber size incresed. This indictes the importnce of nutrient vilble storge in the seed tubers. 3.3.Dys to Dormncy Breking Achieved results of these experiments reveled tht the ppliction of plnt growth regultor hormones cuses significnt differences in the number of dys to brek dormncy in compre to control. It is worth noting tht the difference creted by the gibberellic cid in turn ws different from the other two hormones. The lowest Dy to brek dormncy ws observed in gibberellic cid hormone ppliction by the rte of 33.50 dys which in comprison to highest rte observed in control plots (54.7), the difference is significnt nd unvoidbly(tble 2). Dogondze et l,[7] reported tht with respect to tht in ddition bscisic cid nother ingredients involved in tuber nturl dormncy, ppliction of gibberellic cid on dormnt tubers cn reduce endogenous bscisic cid of tubers. The reports lso stte tht gibberellic cid cuses brekdown of strches nd ccumultion of renewble sugrs in potto tubers which this issue tht cn stimultes the germintion nd consequently the dormncy breking [1,10]. Some other reports hs been stted tht dipping the seeds with gibberellic cid before plnting for n hour, will brek seed dormncy of the potto [13]. However, we hve to consider the fct tht excessive use of gibberellic cid cuses disorders such s stem elongtion [14] excessive growth of the shoots, tuber deformities, dely in tuber ngiogenesis nd reduction in root formtion. Dys to brek dormncy in Agri ws lower thn the result Burren cultivr showed. Differences in this chrcteristics hve been observed in different vrieties in the other experiments. In Slimi et l., [16] experiments lso Burren nd Agri cultivr chieved longest nd shortest dormncy period. Men comprison tble shows tht the verge dormncy durtion inversely with the mount of seed size(tble2). This mens tht whtever size of the tuber hs grown bigger dormncy period fell by. It cn be sid tht this is probbly due to the lrger potto seeds contin higher levels of dormncy inhibitors. Results of this study were similr to results reported in erlier studies [15]. 100
Frshid Hssni et l Euro. J. Exp. Bio., 2014, 4(4):98-102 Tble 1- Anlysis of vrince for lbortories trits SOV Degree of Freedom Dys to Sprouting Totl number of sprouting Dys to Dormncy Breking Growth stimulnts(a) 3 519.29 ** 1.51 ** 2220.59 ** Vriety (B) 1 37.76 ** 3.36 ** 319.01 ** Mini-tuber size (C) 3 18.08 ** 1.90 ** 204.84 ** A * B 3 35.83 ** 0.03 ns 26.68 * A * C 9 2.20 ** 0.17 * 37.51 ** B * C 3 8.65 ** 0.50 ** 20.98 ns A * B * C 9 1.08 ns 0.09 ns 14.50 ns Error 62 43.01 0.07 9.33 CV ------- 4.35 15.59 7.53 *, ** nd ns: Significnt t the 5% nd 1% level of probbility nd non-significnt, respectively. Tble 2- Men comprison of min effects Dys to Totl number of Dys to Dormncy Breking Experimentl Tretment Sprouting(dy) sprouting (dy) Control (wsh by wter) ( 1) 25.24 d 1.41 c 54.75 c gibberellic cid ( Growth stimulnts (A) 2) 13.99 1.71 b 33.50 crbon disulfide ( 3) 18.04 b 1.76 b 37.58 b Thioure( 4) 19.13 c 2.03 36.75 b gri (b Vriety (B) 1) 19.73 b 1.54 b 36.85 b Burren (b 2) 18.47 1.92 33.23 12-20 (c 1) 19.60 b 1.47 c 45.54 b 20-25 (c Mini-tuber size (C) 2) 19.36 b 1.52 c 42.54 b 25-30 (c 3) 19.62 b 1.87 b 38.45 30-35 (c 4) 17.81 2.06 37.66 Men in ech column, followed by similr letter (s) not significntly different t 5% probbility level, using LSD test. Tble 2- Men comprison of interction effect Experimentl Tretment Dys to Sprouting (dy) Totl number of sprouting Dys to Dormncy Breking (dy) Control (wsh by wter) ( 1) Agri (b 1) Burren (b 2) 25.38 25.11 1.27 1.55 57.50 52.00 b gibberellic cid ( 2) Burren (b 2) 11.56 1.93 31.00 Agri (b 1) 16.42 b 1.50 36.00 b crbon disulfide ( 3) Burren (b 2) 17.82 1.94 34.75 Agri (b 1) 18.27 1.59 38.00 Thioure( 4) Agri (b 1) 18.85 1.80 37.17 Burren (b 2) 19.41 2.25 38.00 12-20 (c 1) 25.53 b 1.35 59.67 c Control (wsh by wter) ( 1) 20-25 (c 2) 25.20 b 1.32 57.67 bc 25-30 (c 3) 26.42 b 1.40 53.33 b 30-35 (c 4) 23.82 1.52 48.33 12-20 (c 1) 15.23 c 1.46 b 39.33 b gibberellic cid ( 2) 20-25 (c 2) 14.52 bc 1.33 b 35.33 b 25-30 (c 3) 13.47 b 1.98 28.83 30-35 (c 4) 12.76 1.35 30.50 12-20 (c 1) 18.29 b 1.56 c 37.33 crbon disulfide ( 3) 20-25 (c 2) 18.45 b 1.83 bc 39.83 25-30 (c 3) 19.15 b 2.31 b 37.17 30-35 (c 4) 16.30 1.83 36.00 12-20 (c 1) 19.38 1.71 b 37.83 Thioure( 4) 20-25 (c 2) 19.28 1.88 b 37.33 25-30 (c 3) 19.48 2.28 34.50 30-35 (c 4) 18.37 2.23 35.83 12-20 (c 1) 19.65 b 1.32 b 45.42 Agri (b 1) 20-25 (c 2) 19.62 1.53 b 43.42 25-30 (c 3) 20.44 b 1.62 b 39.92 30-35 (c 4) 19.20 2.21 40.75 12-20 (c 1) 19.56 b 1.52 b 41.67 Burren (b 2) 20-25 (c 2) 19.09 b 1.80 b 41.67 25-30 (c 3) 18.81 b 1.52 37.00 30-35 (c 4) 16.42 2.31 A 34.58 Men in ech column, followed by similr letter (s) not significntly different t 5% probbility level, using LSD test. 101
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