Mapping quantitative trait loci controlling cool-temperature tolerance at booting stage in temperate japonica rice

Abstract

To identify the chromosomal regions controlling cool-temperature tolerance (CT) at booting stage of rice (Oryza sativa L.), we performed quantitative trait locus (QTL) analysis with doubled-haploid lines (DHLs). We constructed a linkage map with 135 restriction fragment length polymorphism (RFLP) markers and 34 random amplified polymorphic DNA (RAPD) markers using 212 DHLs derived from crosses between two cultivars, Akihikari (moderately cool-temperature susceptible) and Koshihikari (cool-temperature tolerant). Both parental cultivars belong to the temperate japonica group. The degree of tolerance of each DHL was measured as the degree of sterility in the field with a running cold-water system. Three QTLs were mapped one each to chromosomes 1, 7, and 11. The QTL with the largest effect, qCT-7, was mapped to chromosome 7 and explained 22.1% of the total phenotypic variation. The other two QTLs, qCT-1 and qCT-11, explained approximately 5% each. For all of the QTLs, alleles from Koshihikari increased the degree of CT. We also mapped QTLs for heading date and culm length, which are thought to affect CT.