Identification of Quantitative Trait Loci Controlling Cold Tolerance at the Reproductive Stage in Yunnan Landrace of Rice, Kunmingxiaobaigu

This study focused on a Yunnan landrace of rice, Kunmingxiaobaigu, to identify quantitative trait loci (QTLs) controlling cold tolerance at the reproductive stage using DNA markers. A linkage map with 16 linkage groups covering 1,354.4 cM with a total of 122 markers was constructed based on an F-2 population consisting of 250 individuals of a cross between Kunmingxiaobaigu and a Japanese variety, Towada. Nine QTLs were detected by interval mapping in the F-2 population. The nine QTLs were distributed on chromosomes 1 (2 QTLs), 3, 4, 6 (2 QTLs), 7, 10 and 12. The total variance explained by these nine QTLs was 54.2%, while the variance explained by a single QTL ranged from 5.0% to 37.8%. The validity of four QTLs on chromosomes 3, 6 (2 QTLs) and 7 was confirmed by single-marker analysis in the F-3 population and they were designated as qRCT3, qRCT6a, qRCT6b and qRCT7, respectively. The QTLs qRCT3, qRCT6a and qRCT6b were reported here for the first time. The QTL qRCT7 displayed the largest effect, reaching a value of 20.6%.