Developing Isogenic Lines of Japanese Rice Cultivar 'Koshihikari' with Early and Late Heading

Abstract

Four quantitative trait loci (QTLs) for rice (Oryza sativa L.) heading date were previously detected by QTL analysis of progeny derived from crosses between a japonica cultivar, Koshihikari, and an indica cultivar, Kasalath. To enhance the cropping potential of Koshihikari, a leading cultivar in Japan, our team used marker-assisted selection to develop isogenic lines (ILs) with early and late heading dates. Several types of DNA marker were used to minimize the length of substituted chromosome segments containing target QTLs and to determine the genotype in the target QTL regions and in the background genome of the ILs. We developed four new ILs-Koshihikari Kanto HD1 (Hd1), Wakei 370 (Hd4), Kanto IL5 (Hd6), and Kanto HD2 (Hd5)-housing Kasalath chromosome segments of 560, 7960, 170, and 625 kb, respectively. The heading date of Koshihikari Kanto HD1 was 12 days earlier than that of Koshihikari in Ibaraki, and those of Wakei 370, Kanto IL5, and Kanto HD2 were 3, 10, and 11 days later, respectively. Most of the traits, except the heading date of the four ILs, were the same as those of Koshihikari.