Linkage map construction and QTL mapping for cold tolerance in Oryza rufipogon Griff. at early seedling stage

Cold stress is one of the major restraints for rice production. Cold tolerance is controlled by complex genetic factor. In this study, a backcross inbred lines （BILs） population derived from an inter-specific cross （Oryza sativa L.xO. rufipogon Griff.） was used for genetic linkage map construction and quantitative trait locus （QTL） mapping. A linkage map consisting of 153 markers was constructed, spanning 1 596.8 cM with an average distance of 11.32 cM between the adjacent markers. Phenotypic evaluation of the parents and BILs under （6±1）℃ cold stress revealed that the ability of cold tolerance in BILs at early seedling obeyed a skewed normal and continuous distribution. Fifteen QTLs on chromosomes 6, 7, 8, 11, and 12 were identified using survival percent （SP） and non death percent （NDP） as indicators of cold tolerance, which could explain 5.99 to 40.07% of the phenotypic variance, of which the LOD values ranged from 3.04 to 11.32. Four QTLs on chromosomes 3, 5 and 7 were detected using leaf conductivity （LC） and root conductivity （RC） as indicators of cold tolerance, ranging from 19.54 to 33.53% for the phenotypic variance explained and 2.54 to 6.12 for the LOD values. These results suggested that there might be multi major QTLs in O. rufipogon and some useful genes for cold tolerance have been transferred into cultivated rice, which would be helpful for cloning and utilizing the cold tolerance-responsive genes from wild rice.