RFLP mapping and QTL analysis of heading date and pollen sterility using backcross populations between Oryza sativa L. and Oryza glaberrima Steud.

To fully exploit the genetic potential of African rice, Oryza glaberrima Steud., we aimed at developing a series of O. glaberrima introgression lines (GILs) in the background of Japonica rice (O. sativa L. cv. Taichung 65). Each GIL carrying homozygous chromosome segments from O. glaberrima will be selected using RFLP markers. As a first step, an RFLP linkage map based on backcross population (BC₁F₁) was constructed. QTLs for two quantitative traits, male sterility and heading date, were investigated in the BC₂F₁ population. The RFLP map contained 101 well-dispersed RFLP markers. Total map length was 1403.4 cM. Linkage arrangement of the RFLP markers was in good agreement with that of the previously constructed maps. Significant segregation distortions were observed in chromosomes 4, 5, 6 and 11. In chromosome 6, a strong distortion towards O. glaberrima was found. On chromosomes 1, 6 and 10, significant (<1%) QTLs for heading were detected. In the heterozygous condition, O. glaberrima alleles around the RFLP markers C1211 (chromosome 1) and XNpb27 (chromosome 6) delayed heading, while another O. glaberrima allele(s) around XNpb37 (chromosome 10) caused early heading. On chromosomes 3, 7 and 10, significant (< 1%) QTLs for pollen sterility were detected. O. glaberrima allele(s) in these regions reduced the pollen fertility in the heterozygous condition. On chromosome 10, a wide region showed a significant association with the trait, suggesting the existence of a powerful male-sterility gene.