Detection of segregation distortions in an indica-japonica rice cross using a high-resolution molecular map.

We have constructed a high-resolution rice genetic map containing 1383 DNA markers covering 1575 cM on the 12 linkage groups of rice using 186 F2 progeny from a cross between a japonica variety, 'Nipponbare', and an indica variety, 'Kasalath'. Using this high-resolution molecular linkage map, we detected segregation distortion in a single wide cross of rice. The frequencies of genotypes for 1181 markers with more than 176 genotype data were plotted along this map to detect segregation distortion. Several types of distorted segregation were observed on 6 of the chromosomes. We could detect 11 major segregation distortions at ten positions on chromosomes 1, 3, 6, 8, 9, and 10. The strongest segregation distortion was at 107.2 cM on chromosome 3 and may be the gametophyte gene 2 (ga-2). The 'Kasalath' genotype at this position was transmitted to the progeny with about a 95% probability through the pollen gamete. At least 8 out of the 11 segregation distortions detected here are new. The use of the high-resolution molecular linkage map for improving our understanding of the genetic nature and cause of these segregation distortions is discussed.