progeny of Oryza saliva and 0. glaberrisna

      K. TAGUCHI, K. Doi and A. Yoshimura

      Plant Breeding Laboratory, Faculty of Agriculture, Kyushu University, 
      Fukuoka, 812-8581 Japan

    Some QTLs affecting pollen sterility were detected in QTL analysis using a BC2F1 population which was obtained from the cross between Japonica rice (Oryza sativa L. cv. Taichung 65) as a recurrent parent and African rice (0. glaberrima Steud., Acc. IRGC1O4O38) as a donor parent (Doi et a!. 1998). We report here the identification of one of the QTLs detected on chromosome 3.

     Backcrossing with Taichung 65 was continued after the QTL analysis. The BC4F1 plants heterozygous for putative QTL region of chromosome 3 and homozygous for Taichung 65 allele in the other QTLs and Si (Sano 1990) regions were selected using RFLP markers. They were backcrossed with Taichung 65. Resulting BC5F1 plants consisting of 62 plants were used as the mapping population. Spikelets at 1 to 2 days before anthesis were collected from each plant and stored in 70% ethanol. Pollen fertility was estimated as the percentage of pollen grains stainable with 12-KI solution.

     Pollen fertility in the mapping population showed clear bimodal distribution and the population was classified into two groups; semi-sterile and fertile. Plants in semi-sterile group showed approximately 50% pollen fertility and those in the other group showed normal fertility (Fig. 1). Spikelet fertility of semi-sterile and normal plants was almost normal. Segregation ratio of the semi-sterile and normal plants was 29: 30, fitting well with the monogenic segregation. Linkage analysis using RFLP markers revealed that this semi-sterility locus was located in the same region as expected by QTL analysis (Fig. 2). Since no locus affecting such F1 pollen sterility has been reported in this region on chromosome 3, this gene was newly designated as Si9.