Mapping of QTL Controlling Seedling Cold Tolerance Using Recombinant Inbred Lines of Rice (Oryza sativa L.)

Low-temperature stress is common for seedlings of rice (Oryza sativa L.) in early-spring and high-elevation environments.With an objective to identify QTL for seedling cold tole-(rance),a new recombinant inbred line (RIL) population was used to conduct QTL mapping study.Seedling cold tolerance of the RILs and their both parents was assessed based on survival rates of seedlings at 3-leaf stage which was exposed to cold treatment of 3 d at a low-temperature of 10℃.A marked difference between both parents in seedling cold tolerance was observed.The japonica parent Lemont was tolerant to the cold while the indica parent Teqing sensitive to the cold.The RILs displayed approximately continuous trait variations and transgressive segregation was observed in both directions.Composite interval mapping was carried out using a high-density linkage map.Totally,five QTL for seedling cold tolerance were mapped to chromosomes 1,3,8 and 11,respectively,each explaining 7%-21% of the phenotypic variation.Among these QTL,four had their positive alleles from Lemont and the other one from Teqing.Two major QTL for the trait were identified on chromosomes 3 and 8,respectively,with much higher LOD scores.They individually accounted approximately for 20% of the phenotypic variation.The Lemont alleles at the two major QTL increased the trait values.These results showed the genetic diversity of QTL for seedling cold tolerance and indicated that japonica tolerant to cold was the major germplasm resource carrying favorable genes conferring seedling cold tolerance in rice.