Study On QTL Mapping Of Cold Tolerance During Early Growth Period In Rice

Rice is one of the important food crops in the world, which originates from tropic and subtropical area. At present, it's an important objective to breed a rice variety with cold tolerance capability due to it usually has sensitivity to low temperature. This study was conducted to analyze correlation of cold tolerance traits among the three early growth stages (germinating stage, budding stage, seedling stage) and detect the quantitative trait loci (QTL) associated with cold tolerance in rice using a backcross inbred lines (BILs) which derived from a backcross of Koshihikari (japonica)/Kasalath(indica)//Koshihikari. The obtained results were described as follows:1. Normal distribution and transgressive segregations for the three cold tolerance traits during early growth period in rice were observed in BILs population, showing that they are quantitatively inherited traits. Furthermore there were not significant correlations among the three periods, indicating that the genetic mechanism of the three stages is discordant.2. A total of 29 QTLs controlling cold tolerance during early growth period in rice were detected and located on chromosome 1, 3, 4, 6, 7, 9, 11 and 12, respectively, which explained 4.0%-33.5% of the observed phenotypic variance.3. QTLs associated with cold tolerance during early growth period in rice can be detected repeatedly between the intervals of C161-R87, C515-C721, C813-C86 on chromosome 1, the interval of R1807-C479 on chromosome 7, the interval of S10928-G4001 on chromosome 11 and the interval of C449-R1709 on chromosome 12, showing that these genomic regions pay important role in cold tolerance during early growth period in rice.4. The japonica parent Koshihikari has a strong cold tolerance while the indica parent Kasalath has a weak cold tolerance. However, some alleles from Kasalath with positive effects for cold tolerance were detected, indicating it's possible to excavate cold tolerance genes from cold sensitive rice materials.5. Both one QTL associated with the reduction of chlorophyll content and one major QTL, qCTS-12-1, for crimp of leaf caused by low temperature were located on the same molecular marker interval of C449-R1709 on chromosome 12. Then through further genetic mapping, qCTS-12-1 was located on the physical distance about 77kb, which possess 19 candidate genes.In this study, the QTLs related with cold tolerance during early growth period in rice were detected by using BIL between Koshihikari and Kasalath and these QTLs can lie foundation for molecular marker-assisted selection (MAS) breeding, the further fine mapping and cloning of cold tolerance QTL.