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 AT307 Kumr APA 1, Dhnyke Nilnthi 1 *, Phthinyke BD 2 nd 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 Accepted: 25 Mrch 2014 Tropicl Agriculturl Reserch & Extension 16(2): ABSTRACT Rice is considered s self-pollinted crop ut out-crossing is possile. At307 is high yielding, 90d vriety developed t the Rice Reserch Sttion, Amlntot, Sri Lnk possessing good ttriutes to e recommended s commercil vriety in Sri Lnk. It contins oth Indic nd Jponic germplsms. At307 hs filed to pss the seed certifiction severl times due to lck of its genetic purity perhps due to out -crossing nture, or mechnicl mixing. Therefore the present study ws conducted to investigte the chrcteristics ssocited with out -crossing of At307. Comprison ws done with Bg300, Bg304, At303 nd At306 improved 90d rice vrieties t Amlntot rice reserch sttion during the Yl seson, Out crossing minly depends on flowering ehvior, florl chrcteristics of mle nd femle prts nd vrition in environmentl fctors. Vrietl differences were found to e significnt t 5% proility level for spikelet open ngle. But spikelet open durtion, numers of spikelet per pnicle (NS/P), stigm exsertion percentge, flowering period of plnt, culm length), pnicle length. Flowering period of pnicle, ngle of flg lef, length of flg lef nd width of flg lef were not significntly different mong five selected rice vrieties. Out-crossing ssocited chrcters of At307 were norml except spikelet opening ngle. Incresed exposes the stigm more to lien pollens resulting emerges off-types in future genertion of At307. Key words: Out- crossing, Oryz stiv. spikelet opening ngle, At307 INTRODUCTION Sri Lnk hs chieved remrkle progress in rice yield improvement with the introduction of new improved rice vrieties developed t the rice reserch sttions t Btlgod (Bg), Bomuwl (Bw), Amlntot (At) nd Luduw (Ld). Min ojectives of rice reserch sttion t Amlntot in Sri Lnk hs een to develop short-ge red rice, resistnt to slinity, high yields nd increse qulity of rice grin nd resistnt to pest nd disese. It hs lredy developed numer of rice vrieties like At303, At353, At354, At401, At402, At405, At362, At306, At307 nd At308. At307 is high yielding 90d rice vriety (pedigree- Bg nd Bg ) which ws relesed in 2005 nd recommended for generl cultivtion. It hs high yield potentil (8t/h) nd is resistnt to Brown plnthopper, Gll Midge, Bcteril Lef Blight nd Blst. The plnt hs sturdy culm. At307 hs filed seed certifiction in reeder seed, *Corresponding uthor: nilnthi@gio.ruh.c.lk certified seed, foundtion seed nd register seed stges in severl times due to emerging off-types which cn e out-crossing, genetic purity prolem or mechnicl error. Though rice is 99% self-pollinted crop it hs een oserved to hve out-crossing potentil up to 6-8% in some vrieties under certin conditions (Shdevn nd Nmoodiri 1963). Crossing depends on flowering ehvior, florl chrcteristics of mle nd femle prts nd vrition in environmentl fctors. Present experiment ws conducted to study the outcrossing ssocited chrcteristics of At307 with other improved 90d rice vrieties (Bg300, Bg304, At303 nd At306). MATERIALS AND METHODS The experiment ws crried out t the Rice Reserch Sttion, Amlntot from My to Septemer in At307, Bg300, Bg304, At303 nd At306 90d vrieties were selected to test out-crossing ssocited chrcters under locl

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3 61 OUT CROSSING OF RICE (Oryz stiv L) VARIETY AT307 condition. Culturl prctices were done ccording to the recommendtion of the Deprtment of Agriculture. Associted out-crossing chrcteristics were mesured t heding stge to flowering stge. The mesurements were tken s follows; Culm Length (cm), Pnicle length (cm), Flg lef length (cm), Flg lef width (cm), Flg lef ngle (degree), Durtion of spikelet opening (min), Spikelet opening ngle ( o ), Pnicle opening durtion (dys), Flowering period of plnt (hr), Numers of spikelets per pnicle, Stigm exertion Percentge (Percentge of stigm come out when spikelet closing) = Spikelets of stigm exserted x 100 Totl spikelets in pnicle Rndomized Complete Block Design (RCBD) with five replictes ws used. Tretments were rndomized using rndom tle. Twenty five pots were used for experiment with four plnts per one pot. Vrince ws done t the 0.05 significnt levels y using SAS pckge (v6.12) (SAS Institute, Cry NC, 1995). RESULTS AND DISCUSSION One hundred rice plnts elong to five vrieties were rrnged in the reserch field t Rice Reserch Sttion, Amlntot, Sri Lnk. All mngement prctices were conducted ccording to recommendtions of the Deprtment of Agriculture from seed germintion to flowering. Significnt out-crossing ssocited chrcters Out-crossing potentil is normlly depended on some morphologicl nd florl chrcteristics of rice plnt (Virmni Snt, 1994). Spikelet open ngle, Pnicle length, Numers of spikelet per pnicle, Stigm exsertion percentge, Flowering period of pnicle, Flowering period of plnt, Spikelet open durtion, Angle of flg lef, Length of flg lef, Width of flg lef nd Culm length of selected five rice vrieties were tested. Vrietl differences were found to e significnt t 5% proility level for some of these chrcteristics of five selected rice vrieties. Spikelet open ngle (SOA) hs mde significnt influence for out-crossing in rice plnt under locl condition. Higher out-crossing rte ws lwys ssocited with higher Spikelet open ngle due to ility of shedding high mount of pollen grins. Aesekr et l, 2003 lso reported tht SOA highly influence on out-crossing rte of Cytoplsm Mle Sterile (CMS) line under locl condition. At307 hs significntly higher SOA thn other four vrieties (Tle 1). So, out-crossing potentil cn e incresed in At307 thn other vrieties due to higher SOA. Spikelet open durtion (SOD) is lso importnt chrcter to increse out- crossing in rice plnt. It hs een reported y Aesekr et l, 2003 under locl condition in Cytoplsmic mle sterile line. And lso Nmi, 1987 hs een found tht higher SOD enhnce out-crossing rte in rice plnt. When incresing SOD of spikelet environmentl pollen shedding period ws lso incresed nd then out-crossing cn e occurred in rice vrieties. There re no significnt differences mong SOD of At307, Bg300, Bg304 nd At303 (Tle 1). Though At306 showed higher SOD vlue it hs not reported out-crossing prolem. Virmni Snt, 1994 hs reported higher stigm exsertion percentge (SE) influences outcrossing rte. However Aesekr et l, 2003 reported tht stigm exsertion rte hs no influence on out-crossing rte under locl condition. When some vriety consists with stigm exserted spikelets fter closing lemm nd ple, they cn e crossed with pollen grins of other vrieties. Generlly, cultivted rice showed lower stigm exsertion rte compred to wild rice (Virmni Snt, 1994). Stigm exsertion percentge of At307 ws not significntly higher from other vrieties (Tle 1). Although At306 nd Bg304 hve showed higher stigm exsertion percentge, they were not reported out-crossing prolem.

4 Tropicl Agriculturl Reserch & Extension 16(2): Culm length is the other importnt plnt chrcter which lso ffecting nturl out- crossing of rice. Aesekr et l reported tht vrition in plnt height hs no influence on out-crossing rte under locl condition. Bg300 nd Bg304 showed significntly higher culm lengths compred of At307 (Fig 1 D). However these two vrieties hve not out-crossing prolem in the field. Higher totl numers of spikelet nd pnicle exsertion rte were ssocited with higher out -crossing rte in CMS line. Virmni Snt, 1994 nd Aesekr et l, 2003 hve lso reported tht ws essentil to ttin high outcrossing rte. Both vrieties, At307 nd Bg300 hve showed significntly higher numers of spikelets per pnicle (Fig. 1 E). However Bg300 hs not reported out-crossing prolem. Flowering period of plnt (FPOP) is importnt out-crossing relted chrcter of rice. When flowering period is longer, it influences outcrossing y exposing for pollen of other vrieties in the environment. Similr results were reported Ydv et l, 2005 tht looming durtion of pnicles enhnced out-crossing ility of rice. However At307 did not show significntly higher FPOP in this study (Fig. 1F). At 306 showed higher FPOP thn other four vrieties. Non significnt out-crossing ssocited chrcters Pnicle length, Flowering period of pnicle, Angle of flg lef, Flg lef length nd flg lef width of the vrieties did not show ny significnt difference in this study. Chinese rice scientists hve suggested tht smll nd horizontl flg lef is useful to enhnce the out-crossing rte compred to long nd erect flg lef (Virmni Snt, 1994). Other importnt chrcters for outcrossing Florl trits of the seed prent which hve een found to enhnce out-crossing potentil in rice include longer period of stigm receptivity nd lrge nd fethery stigm (Virmni Snt, 1994). Such vrieties were found to hve lrger numer of protruding stigm. Therefore, Kto nd Nmi, 1987 considered tht stigm protrusion contriutes to high nturl out-crossing rte in rice. In ddition Ydv et l, 2005 reported percentge of residul pollen nd the durtion of pollen viility enhnced out-crossing. Further Kto nd Nmi, 1987 hve een found protruded stigm nd higher residul pollens re improving out-crossing rte in tropicl jponic rice. Therefore stigm chrcters should lso e studied to understnd resons for outcrossing of At307. Normlly nther dehiscence nd extrusion occur simultneously so tht the stigm of flower receives pollen from the sme flower in rice plnt. However this process of At307 hs not een studied. Rice pollen grins fter shedding from the nther re comprtively short-lived nd generlly lose their viility within 5 min under ordinry conditions (Virmni Snt, 1994) in some exceptionl cses few pollen grins remin vile for 15 min (Kog et l, 1971). On the other hnd, wild rice pollen grins hve longevity of up to 9 min (Ok nd Morishim, 1967). So pollen viility nd stigm viility is the most importnt fctors for out-crossing in rice plnt. When considering lemm nd ple opening time of At307 ws oserved lter thn other four vrieties. When opening spikelets of At307, lrge mount of pollen of other vrieties spred to the environment tht cn e ffected for out-crossing of At307. Not only morphologicl nd florl chrcters, ut lso environmentl fctors hve significnt role for out-crossing. Virmni Snt, 1994 mentioned tht temperture, reltive humidity, light intensity nd wind velocity re influencing nturl out-crossing in rice. CONCLUSION Out-crossing ssocited chrcters of At307

5 Spikelet open durtion (min) Flowering period of plnt (Dys) Spikelet open ngle (Degree) Numers of spiklets per pnicle 63 OUT CROSSING OF RICE (Oryz stiv L) VARIETY AT307 re in norml rnge except spikelet opening ngle (SOA). Incresed SOA exposes the stigm more to lien pollens resulting of emerging off-types in future genertion of At307. At307 is the highest yielding 90d rice vriety which produces only pnicle erings tillers. If At 307 cultivtes in isolted fields, it hs good potentil to overcome the outcrossing seed pddy production. At307 my e potentil vriety for out-crossing to use in hyrid rice development c c 100 d 50 0 D Rice vrieties d A Rice v rie tie s Rice v rie tie s Culm length (cm) Stigm exsertion percentge d E Rice v rie tie s Rice v rie tie s c B F Fig. 1: Out-crossing ssocited chrcters of the rice vrieties (Mens fllowed y the sme lower cse letters in ech r re not significntly different t 5% level Duncn s Multiple Rnge Test) Authors contriutions 0 C Rice v rie tie s KAPA - Crried out the field experiments, prticipted in the design of the study, dt collection nd drfted the mnuscript. DN - Prticipted in the design of the study, per-

6 formed the sttisticl nlysis nd writing the mnuscript. PBD - Conceived the study, prticipted in the design nd coordintion of ctivities, collorted in otining funds for the study; SSGJN- Prticipted in the design of the study nd sttisticl nlysis. Tropicl Agriculturl Reserch & Extension 16(2): nology, Kumrgnj, Fizd , Indi REFERENCES Aesekr SW, Aesiriwrdn DSDEZ nd Dehideniy EMGJPK Chrcteristics ssocited with out-crossing rte of cytoplsmic mle sterile (CMS) lines in rice under locl condition, Annls of the Sri Lnk deprtment of griculture 5:1-6 Centrl Bnk Annul report of yer Centrl Bnk, Colomo, Sri Lnk. Nmi H Florl structure nd ehvior in reltion to outcrossing in rice. Lecture Hndout, Hyrid Rice Seed Production Trining Course, IRRI, Mnil, Philippines, Sept Ok HI nd Morishim H Vritions in the reeding systems of wild rice, Oryz perennis. Evolution 21: Kog Y, Akihm T, Fujimki H nd Yokoo M Studies on the longevity of pollen grins of rice Oryz stiv L. I. Morphologicl chnges of pollen grins fter shedding Cytologi 36: SAS Institute, Cry, NC, 1995 Shdevn PC nd Nmoodiri KMN 1963.Nturl crossing in rice. Proc Indin Acd Sci Sect B58: Virmni Snt S Outcrossing Mechnisms nd Hyrid Seed Production Prctices in Rice, Heterosis nd Hyrid Rice Breeding, pp.3,9, Ydv RDS, Singh GR nd Srivstv JP Enhncing outcrossing potentil in hyrid rice.pp 20-21, Seed Technology Reserch Centre, Nrendr Dev University of Agriculture nd Tech-