QTL Basic Analysis For Cold Tolerance In Rice (Oryza Sativa L.)

Rice is one of the most important crops in the world, it has become the model crop in monocotyledons for genetic and genomic studies. Chilling injury of rice is a common problem which is encountered in the course of rice cultivation, especially in double harvest rice region, It result in rotting rice sprout and reduce the yield of rice because of low temperature at the early period . Cold tolerance is controlled by some quantitative trait loci (QTL) in rice . This makes genetic study and breeding more difficult. In recent two decades , with constructing of high density molecular linkage map , QTL mapping of rice has got great achievement for quality, resistance and some other important agronomic traits . However, the study for QTLs mapping needs to be furthered because of diversity of global germplasm resource and speciality of QTLs . The study was based on 200 individuals of a F2 separate population and 200 individuals of a F3 lines group which derived from an elite cross of "Milyang23/Jilengl". The genetic variation of cold tolerance at the budburst period, correlation among some agronomic traits under natural condition and cold irrigation, and QTL related with cold tolerance at the budburst period and some agronomic traits under cold irrigation and its CRI (cold response index) were analysed. The result were summaried as follows. (1) In F3 line group, all examined agronomic traits and cold tolerance of budburst displaycontinuous variation and approximately normal distribution, indicating all of these traitswere quantitative inherited . (2 ) Panicle length, seed setting rate and spikelet per panicle were positively correlated withculm length, and the spikelet per panicle and culm length were positively correlatedwith panicle length under natural condition, while panicle length, spikelets per paniclewas positively correlated with culm length, and seed setting rate and spikelets perpanicle was positively correlated with panicle length.(3) A molecular linkage map of 96 SSR markers was constructed by using internal mapping, and covered a total length of 1321.4cM with an average distance of 13.76cM between adjacent markers in rice genome(4) Total 6 QTLs for cold tolerance at the budburst period were detected on chromosome 2 , 4 , 7, 8 and 9 by using internal mapping. They possess additive gene and are controlled by some minor genes, their degree of dominant is smaller. Therefore, they possess high hereditary capacity and can select in low generation.(5) Under cold water treatment, total 10 QTLs for major agronomic traits were detected on chromosome 1, 6, 7, 11 and 12, respectively. These QTLs includes 1 QTL for culm length, 4 QTLs for panicle length, 2 QTLs for seed setting rate, 3 QTLs for spikelets perpanicle.(6) Total 5 of QTLs for cold water response index were detected on chromosome land 6, includes 3 QTLs for CRI of panicle length, 1 QTL for CRI of spikelets per panicle, 1 QTL for CRI of seed setting rate .