DETECTION OF SEGREGATION DISTORTIONS IN AN INDICA-JAPONICA RICE CROSSUSING 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 1 86 F-2 progeny from a cross between a japonica variety, 'Nipponbare', and an indica variety, 'Kasalath'. Using this high-resolution molecula r linkage map, we detected segregation distortion in a single wide cro ss of rice. The frequencies of genotypes for 1181 markers with more th an 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 s egregation distortion was at 107.2 cM on chromosome 3 and may be the g ametophyte gene 2 (ga-2). The 'Kasalath' genotype at this position was transmitted to the progeny with about a 95% probability through the p ollen gamete. At least 8 out of the 11 segregation distortions detecte d here are new. The use of the high-resolution molecular linkage map f or improving our understanding of the genetic nature and cause of thes e segregation distortions is discussed.