QTL Mapping Of Seed Vigor Under Two Temperature Conditions In Rice

Rice(Oryza sativa L.)is an important food crop,which originated from tropical and subtropical regions,and is sensitive to low temperature condition(15 ?).With the rapid development of society and economy of China,the labor shortage is a big issue for rice production.The traditional transplanting of rice(TPR)has been gradually replaced by the method of direct seeding of rice(DSR)due to its lower cost and its operational simplicity.Seeds with high vigor have a better performance of seed germination,seedling emergence and uniform growth in fields.Therefore,it is important for DSR method that rice varity has high seed vigor.The improvement of seed vigor is an important issue in rice breeding.In this study,the QTL mapping for seed vigor was carried out under different temperatures conditions(25? and 15?)using different populations of rice.The main results are as follows:1.Using two F2 populations of rice(9311/Daguandao and IR28/Daguandao),QTL mapping for seed vigor was conducted under normal condition(25?).Results showed that the indica 9311 and IR28 had higher seed vigor than the japonica Daguandao.Using 3 d,7 d germination rate(GR)and 7 d germination index(GI),12 and 4 SSR markers linked with seed vigor were detected,respectively,in 9311/Daguandao and IR28/Daguandao F2 populations by BSA(Bulk Segregant Analysis,BSA)method.Of them,the SSR marker RM4108 located on chromosome 3 was simultaneously detected in both populations.Furthermore,9311/Daguandao F2 population was used to verify QTL and to estimate QTL effects.Finally,six QTLs were detected;of them,qGR3.2 can explain 8.29%of total phenotypic variation,while other five major QTLs can explain 23.84%-36.59%of total phenotypic varation.The SSR markers RM4108 located on chromosome 3 which closely linked to seed vigor was confirmed.2.Using chromosome segment substitution lines(CSSLs),origined from the cross of Jiucaiqing(donor)and IR26(receptor),QTL mapping for seed vigor under two temperature conditions(25? and 15?)were conducted.Result showed that the indica IR26 had higher seed vigor than the japonica Jiucaiqing under both conditions.Using 3 d,7 d germination rate(GR)and 7 d germination index(GI),eight SSR markers linked to seed vigor were detected on chromsomes 1,2,3,6 and 7 respectively under normal condition(25?).Meanwhile,using 12 d,15 d germination rate(GR)and 15 d germination index(GI),12 SSR markers linked to seed vigor were detected on chromosomes 2,3,4,6,7,8,9,11 and 12 respectively under low temperature condition(150C).Among these QTLs,five QTLs were simultaneously detected under both conditions.However,seven QTLs qLTG4.1,qLTG5.1,qLTG8.1,qLTG9.1,qLTG9.2,qLTG11.1 and qLTG11.2 were specific for low temperature condition.By comparison,four QTLs qNTG3.2,qLTG4.1,qLTG5.1 and qLTG8.1 located on chromosomes 3,4,5 and 8 respectivel might have important role(s)in seed vigor.Several seed vigor-related QTLs identified in previous studies were found to be near the 17 QTLs detected here,while qLTG9.1 for low temperatue germination might represent novel gene.