Analysis of Quantitative Trait Loci for Cold Tolerance at the Booting Stage of Rice

We analyzed the quantitative trait loci (QTLs) for cold tolerance at the booting stage of a cold-tolerant rice variety, Norin-PL8, which harbors cold tolerance genes derived from a cold-tolerant variety, Silewah. We foundthat 5 segments on chromosomes 1 (2 segments), 3, 4 and 8 were incorporated from Silewah into Norin-PL8. The association between the incorporated segments and cold tolerance was examined using BC 1 F 5 lines between Norin-PL8 and Kirara397, which is a cold-sensitive commercial variety. The segment on the short arm of chromosome 3 and that on the long arm of chromosome 4 were associated with cold tolerance, indicating the presence of QTLs for cold tolerance on chromosomes 3 and 4. Interval mapping on the long arm of chromosome 4 suggested that 2 QTLs were located in the centromeric half of the incorporated segment. In order to confirm the results of interval mapping, we developed a set of near-isogenic lines (NILs). Comparison of the levels of cold tolerance of the NILs indicated that either the proximal end or the center of the segment is necessary for cold tolerance. Based on these results, it was concluded that there are at least 3 QTLs for cold tolerance on chromosomes 3 and 4.