RFLP linkage map included the information of segregation distortion in a wide-cross population between Indica and Japonica rice (Oryza sativa L.)

A new rice (Oryza sativa L.) linkage map of DNA markers was developed using 119 restriction fragment length polymorphism (RFLP) markers in 202 F-2 pro geny derived from a cross between a Korean variety, Milyang 23, and a Japan ese variety, Akihikari which belonged to cv, gr, Indica and cv, gr, Japonic a, respectively. The F-2 linkage map covered a total distance of 1355 cM on the 12 rice chromosomes. Non-polymorphic markers were recognized continuou sly on the distal region of the short arm of chromosome 5 at a length of 30 cM, which was not covered by RFLP analysis. The orientation, chromosome nu mber of these 12 linkage groups and positions of centromere were determined and assigned to their respective chromosomes, as described by Harushima et al, (1998), In the F-2 population, segregation distortions were detected i n a total of 16 chromosome regions except for chromosomes 1 and 4, Among th em, ten and four chromosome regions showed an increased number of progeny w ith genotypes of Indica and Japonica homozygotic alleles, respectively. Two other regions showed an increase in Indica/Japonica heterozygotes, Skew in favor of Indica alleles was recognized on chromosomes 2 and 3 (two regions ); 5, 6, 9 and 11 (two regions); and 12 (two regions), and that of Japonica on chromosomes 7, 8 and 10 (two regions). An increase of heterozygote was detected on chromosomes 2 and 9, Such segregation distortions may be due to reproductive barriers, i.e., hybrid sterility, gametophyte genes and hybri d weakness. Such information on segregation distortions is valuable for in wide hybridization breeding between Indica and Japonica varieties. The F-2 population, RFLP segregation data and the linkage map including the informa tion of distortion should be useful for genetic analysis of agricultural tr aits related to the yield component and for planning breeding programs cons idering the segregation distortions. This study will be a starting point fo r the QTL analysis for agronomic traits and molecular breeding for high yie ld using DNA markers.