RFLP Linkage Map included the Information of Segregation Distortion in a Wide-Cross Population between Indica and Japonica Rice : Oryza sativa L.

Abstract

A new rice (Oryza sativa L.) linkage map of DNA markers was developed using 119 restriction fragment length polymorphism (RFLP) markers in 202 F₂ progeny derived from a cross between a Korean variety, Milyang 23, and a Japanese variety, Akihikari which belonged to cv.gr.Indica and cv.gr.Japonica, respectively. The F₂ linkage map covered a total distance of 1335 cM on the 12 rice chromosomes. Non-polymorphic markers were recognized continuously 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 number of these 12 linkage groups and positions of centromere were determined and assigned to their respective chromosomes, as described by Harushima et at.(1998). In the F₂ population, segregation distortions were detected in a total of 16 chromosome regions except for chromosomes 1 and 4. Among them, ten and four chromosome regions showed an increased number of progeny with 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 hybrid weakness. Such information on segregation distortions is valuable for in wide hybridization breeding between Indica and Japonica varieties. The F₂ population, RFLP segregation data and the linkage map including the information of distortion should be useful for genetic analysis of agricultural traits related to the yield component and for planning breeding programs considering the segregation distortions. This study will be a starting point for the QTL analysis for agronomic traits and molecular breeding for high yield using DNA markers.