Mapping of Quantitative Trait Loci Associated with Cold Tolerance at the Post-Germination Stage in Rice

Cold tolerance at the post-germination stage in rice was studied using gained shoot length (GSL) as a new parameter, which was measured as increased shoot length during cold stress at 4°C followed by a 4-day recovery period at 35°C. GSL decreased until 4 th day in both japonica and indica cultivar, while a marked increase occurred in a japonica cultivar after 5 days of cold stress, indicating its higher ability of cold acclimation. Quantitative trait loci (QTLs) associated with cold tolerance were identified using recombinant inbred lines derived from these parents on a linkage map constructed with 102 simple sequence repeat (SSR) markers. By the interval analysis, one and five putative QTLs were identified after 5 and 11 days of cold stress, respectively. The single point analysis indicated that these QTLs explained 16% and 54% of the phenotypic variance after 5 and 11 days of cold stress, respectively. A cold tolerant japonica parent contributed all QTLs, among which one on the long arm of chromosome 7 was common for the two cold stress periods. Based on gained root length one QTL was identified on chromosome 12 explaining 11% of the variance.