CHARACTERISTICS ASSOCIATED WITH OUT CROSSING IN A SHORT DURATION IMPROVED RICE (Oryza sativa L) VARIETY AT307

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1 CHARACTERISTICS ASSOCIATED WITH OUT CROSSING IN A SHORT DURATION IMPROVED RICE (Oryz stiv L) VARIETY AT37 Kumr APA 1, Dhnyke Nilnthi 1 *, Phthinyke BD 2 n Sennyke SGJN 1 1 Deprtment of Agriculturl Biology, Fculty of Agriculture, University of Ruhun, Mpln, Kmurupitiy, Sri Lnk 2 Rice Reserch Sttion, Amlntot, Sri Lnk Accepte: 25 Mrch 214 ABSTRACT Rice is consiere s self-pollinte crop ut out-crossing is possile. At37 is high yieling, 9 vriety evelope t the Rice Reserch Sttion, Amlntot, Sri Lnk possessing goo ttriutes to e recommene s commercil vriety in Sri Lnk. It contins oth Inic n Jponic germplsms. At37 hs file to pss the see certifiction severl times ue to lck of its genetic purity perhps ue to out-crossing nture, or mechnicl mixing. Therefore the present stuy ws conucte to investigte the chrcteristics ssocite with out-crossing of At37. Comprison ws one with Bg3, Bg34, At33 n At36 improve 9 rice vrieties t Amlntot rice reserch sttion uring the Yl seson, 21. Out crossing minly epens on flowering ehvior, florl chrcteristics of mle n femle prts n vrition in environmentl fctors. Vrietl ifferences were foun to e significnt t 5% proility level for spikelet open ngle. But spikelet open urtion, numers of spikelet per pnicle (NS/P), stigm exsertion percentge, flowering perio of plnt, culm length), pnicle length. Flowering perio of pnicle, ngle of flg lef, length of flg lef n with of flg lef were not significntly ifferent mong five selecte rice vrieties. Out-crossing ssocite chrcters of At37 were norml except spikelet opening ngle. Increse exposes the stigm more to lien pollens resulting emerges off-types in future genertion of At37. Key wors: Out- crossing, Oryz stiv. spikelet opening ngle, At37 INTRODUCTION Sri Lnk hs chieve remrkle progress in rice yiel improvement with the introuction of new improve rice vrieties evelope t the rice reserch sttions t Btlgo (Bg), Bomuwl (Bw), Amlntot (At) n Luuw (L). Min ojectives of rice reserch sttion t Amlntot in Sri Lnk hs een to evelop short-ge re rice, resistnt to slinity, high yiels n increse qulity of rice grin n resistnt to pest n isese. It hs lrey evelope numer of rice vrieties like At33, At353, At354, At41, At42, At45, At362, At36, At37 n At38. At37 is high yieling 9 rice vriety (peigree- Bg n Bg ) which ws relese in 25 n recommene for generl cultivtion. It hs high yiel potentil (8t/h) n is resistnt to Brown plnthopper, Gll Mige, Bcteril Lef Blight n Blst. The plnt hs stury culm. At37 hs file see certifiction in reeer see, *Corresponing uthor: nilnthi@gio.ruh.c.lk certifie see, fountion see n register see stges in severl times ue to emerging off-types which cn e out-crossing, genetic purity prolem or mechnicl error. Though rice is 99% self-pollinte crop it hs een oserve to hve out-crossing potentil up to 6-8% in some vrieties uner certin conitions (Shevn n Nmooiri 1963). Crossing epens on flowering ehvior, florl chrcteristics of mle n femle prts n vrition in environmentl fctors. Present experiment ws conucte to stuy the outcrossing ssocite chrcteristics of At37 with other improve 9 rice vrieties (Bg3, Bg34, At33 n At36). MATERIALS AND METHODS The experiment ws crrie out t the Rice Reserch Sttion, Amlntot from My to Septemer in 21. At37, Bg3, Bg34, At33 n At36 9 vrieties were selecte to test out-crossing ssocite chrcters uner locl

2 61 conition. Culturl prctices were one ccoring to the recommention of the Deprtment of Agriculture. Associte out-crossing chrcteristics were mesure t heing stge to flowering stge. The mesurements were tken s follows; Culm Length (cm), Pnicle length (cm), Flg lef length (cm), Flg lef with (cm), Flg lef ngle (egree), Durtion of spikelet opening (min), Spikelet opening ngle ( o ), Pnicle opening urtion (ys), Flowering perio of plnt (hr), Numers of spikelets per pnicle, Stigm exertion Percentge (Percentge of stigm come out when spikelet closing) = Spikelets of stigm exserte x 1 Totl spikelets in pnicle Rnomize Complete Block Design (RCBD) with five replictes ws use. Tretments were rnomize using rnom tle. Twenty five pots were use for experiment with four plnts per one pot. Vrince ws one t the.5 significnt levels y using SAS pckge (v6.12) (SAS Institute, Cry NC, 1995). RESULTS AND DISCUSSION OUT CROSSING OF RICE (Oryz stiv L) VARIETY AT37 One hunre rice plnts elong to five vrieties were rrnge in the reserch fiel t Rice Reserch Sttion, Amlntot, Sri Lnk. All mngement prctices were conucte ccoring to recommentions of the Deprtment of Agriculture from see germintion to flowering. Significnt out-crossing ssocite chrcters Out-crossing potentil is normlly epene on some morphologicl n florl chrcteristics of rice plnt (Virmni Snt, 1994). Spikelet open ngle, Pnicle length, Numers of spikelet per pnicle, Stigm exsertion percentge, Flowering perio of pnicle, Flowering perio of plnt, Spikelet open urtion, Angle of flg lef, Length of flg lef, With of flg lef n Culm length of selecte five rice vrieties were teste. Vrietl ifferences were foun to e significnt t 5% proility level for some of these chrcteristics of five selecte rice vrieties. Spikelet open ngle (SOA) hs me significnt influence for out-crossing in rice plnt uner locl conition. Higher out-crossing rte ws lwys ssocite with higher Spikelet open ngle ue to ility of sheing high mount of pollen grins. Aesekr et l, 23 lso reporte tht SOA highly influence on out-crossing rte of Cytoplsm Mle Sterile (CMS) line uner locl conition. At37 hs significntly higher SOA thn other four vrieties (Tle 1). So, out-crossing potentil cn e increse in At37 thn other vrieties ue to higher SOA. Spikelet open urtion (SOD) is lso importnt chrcter to increse out- crossing in rice plnt. It hs een reporte y Aesekr et l, 23 uner locl conition in Cytoplsmic mle sterile line. An lso Nmi, 1987 hs een foun tht higher SOD enhnce out-crossing rte in rice plnt. When incresing SOD of spikelet environmentl pollen sheing perio ws lso increse n then out-crossing cn e occurre in rice vrieties. There re no significnt ifferences mong SOD of At37, Bg3, Bg34 n At33 (Tle 1). Though At36 showe higher SOD vlue it hs not reporte out-crossing prolem. Virmni Snt, 1994 hs reporte higher stigm exsertion percentge (SE) influences outcrossing rte. However Aesekr et l, 23 reporte tht stigm exsertion rte hs no influence on out-crossing rte uner locl conition. When some vriety consists with stigm exserte spikelets fter closing lemm n ple, they cn e crosse with pollen grins of other vrieties. Generlly, cultivte rice showe lower stigm exsertion rte compre to wil rice (Virmni Snt, 1994). Stigm exsertion percentge of At37 ws not significntly higher from other vrieties (Tle 1). Although At36 n Bg34 hve showe higher stigm exsertion percentge, they were not reporte out-crossing prolem.

3 Culm length is the other importnt plnt chrcter which lso ffecting nturl out- crossing of rice. Aesekr et l. 23 reporte tht vrition in plnt height hs no influence on out-crossing rte uner locl conition. Bg3 n Bg34 showe significntly higher culm lengths compre of At37 (Fig 1 D). However these two vrieties hve not out-crossing prolem in the fiel. Higher totl numers of spikelet n pnicle exsertion rte were ssocite with higher out -crossing rte in CMS line. Virmni Snt, 1994 n Aesekr et l, 23 hve lso reporte tht ws essentil to ttin high outcrossing rte. Both vrieties, At37 n Bg3 hve showe significntly higher numers of spikelets per pnicle (Fig. 1 E). However Bg3 hs not reporte out-crossing prolem. Flowering perio of plnt (FPOP) is importnt out-crossing relte chrcter of rice. When flowering perio is longer, it influences outcrossing y exposing for pollen of other vrieties in the environment. Similr results were reporte Yv et l, 25 tht looming urtion of pnicles enhnce out-crossing ility of rice. However At37 i not show significntly higher FPOP in this stuy (Fig. 1F). At 36 showe higher FPOP thn other four vrieties. Non significnt out-crossing ssocite chrcters Pnicle length, Flowering perio of pnicle, Angle of flg lef, Flg lef length n flg lef with of the vrieties i not show ny significnt ifference in this stuy. Chinese rice scientists hve suggeste tht smll n horizontl flg lef is useful to enhnce the out-crossing rte compre to long n erect flg lef (Virmni Snt, 1994). Other importnt chrcters for outcrossing Florl trits of the see prent which hve een foun to enhnce out-crossing potentil in rice inclue longer perio of stigm receptivity n lrge n fethery stigm (Virmni Snt, 1994). Such vrieties were foun to hve lrger numer of protruing stigm. Therefore, Kto n Nmi, 1987 consiere tht stigm protrusion contriutes to high nturl out-crossing rte in rice. In ition Yv et l, 25 reporte percentge of resiul pollen n the urtion of pollen viility enhnce out-crossing. Further Kto n Nmi, 1987 hve een foun protrue stigm n higher resiul pollens re improving out-crossing rte in tropicl jponic rice. Therefore stigm chrcters shoul lso e stuie to unerstn resons for outcrossing of At37. Normlly nther ehiscence n extrusion occur simultneously so tht the stigm of flower receives pollen from the sme flower in rice plnt. However this process of At37 hs not een stuie. Rice pollen grins fter sheing from the nther re comprtively short-live n generlly lose their viility within 5 min uner orinry conitions (Virmni Snt, 1994) in some exceptionl cses few pollen grins remin vile for 15 min (Kog et l, 1971). On the other hn, wil rice pollen grins hve longevity of up to 9 min (Ok n Morishim, 1967). So pollen viility n stigm viility is the most importnt fctors for out-crossing in rice plnt. When consiering lemm n ple opening time of At37 ws oserve lter thn other four vrieties. When opening spikelets of At37, lrge mount of pollen of other vrieties spre to the environment tht cn e ffecte for out-crossing of At37. Not only morphologicl n florl chrcters, ut lso environmentl fctors hve significnt role for out-crossing. Virmni Snt, 1994 mentione tht temperture, reltive humiity, light intensity n win velocity re influencing nturl out-crossing in rice. CONCLUSION 62 Out-crossing ssocite chrcters of At37

4 Spikelet open urtion (min) Flowering perio of plnt (Dys) Culm length (cm) Spikelet open ngle (Degree) Stigm exsertion percentge Numers of spiklets per pnicle 63 OUT CROSSING OF RICE (Oryz stiv L) VARIETY AT37 re in norml rnge except spikelet opening ngle (SOA). Increse SOA exposes the stigm more to lien pollens resulting of emerging off-types in future genertion of At37. At37 is the highest yieling 9 rice vriety which prouces only pnicle erings tillers. If At 37 cultivtes in isolte fiels, it hs goo potentil to overcome the outcrossing see py prouction. At37 my e potentil vriety for out-crossing to use in hyri rice evelopment At 37 Bg 3 Bg 34 At 33 At 36 D c c c 26 At 37 Bg 3 Bg 34 At 33 At 36 At 37 Bg 3 Bg 34 At 33 At 36 A E At 37 Bg 3 Bg 34 At 33 At At 37 Bg 3 Bg 34 At 33 At 36 B F Fig. 1: Out-crossing ssocite chrcters of the rice vrieties (Mens fllowe y the sme lower cse letters in ech r re not significntly ifferent t 5% level Duncn s Multiple Rnge Test) 4 2 Authors contriutions At 37 Bg 3 Bg 34 At 33 At 36 C KAPA - Crrie out the fiel experiments, prticipte in the esign of the stuy, t collection n rfte the mnuscript. DN - Prticipte in the esign of the stuy, per-

5 forme the sttisticl nlysis n writing the mnuscript. PBD - Conceive the stuy, prticipte in the esign n coorintion of ctivities, collorte in otining funs for the stuy; SSGJN- Prticipte in the esign of the stuy n sttisticl nlysis. 64 Aesekr SW, Aesiriwrn DSDEZ n Dehieniy EMGJPK 23. Chrcteristics ssocite with out-crossing rte of cytoplsmic mle sterile (CMS) lines in rice uner locl conition, Annls of the Sri Lnk eprtment of griculture 5:1-6 Centrl Bnk 29. Annul report of yer 28. Centrl Bnk, Colomo, Sri Lnk. Nmi H Florl structure n ehvior in reltion to outcrossing in rice. Lecture Hnout, Hyri Rice See Prouction Trining Course, IRRI, Mnil, Philippines, Sept Ok HI n Morishim H Vritions in the reeing systems of wil rice, Oryz perennis. Evolution 21: Kog Y, Akihm T, Fujimki H n Yokoo M Stuies on the longevity of pollen grins of rice Oryz stiv L. I. Morphologicl chnges of pollen grins fter sheing Cytologi 36: SAS Institute, Cry, NC, 1995 Shevn PC n Nmooiri KMN 1963.Nturl crossing in rice. Proc Inin Ac Sci Sect B58: Virmni Snt S Outcrossing Mechnisms n Hyri See Prouction Prctices in Rice, Heterosis n Hyri Rice Breeing, pp.3,9,79-16 Yv RDS, Singh GR n Srivstv JP 25. Enhncing outcrossing potentil in hyri rice.pp 2-21, See Technology Reserch Centre, Nrenr Dev University of Agriculture n Technology, Kumrgnj, Fiz , Ini REFERENCES