26. Mapping of a gene for pollen semi-sterility on chromosome 8 of rice

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

Sobrizal et al. (1999) developed the Oryza glumaepatula (IRGC105668) chromosomal segment introgression lines in the background of O. sativa cv. Taichung 65. The O. glumaepatula chromosomal segments were introgressed by repeated backcrossing with Taichung 65 as a recurrent parent. Pollen semi-sterile plants segregated in BC4F2 population. A segregant showing pollen semi-sterile was self-pollinated, then genetic analysis of pollen semi-sterility was performed in BC4F3 population. The parent of BC4F3 population retained O. glumaepatula chromosomal segments on chromosomes 3 and 8 when whole genome survey was conducted to select the candidate plants of O. glumaepatula introgression lines (Sobrizal et al. 1999).

The BC4F3 population showed clear-cut bimodal distribution for pollen fertility when classified into normal and semi-sterile plants (Fig. 1). There were 60 normal and 45 semi-sterile segregants. Semi-sterile plants showed approximately 50% pollen fertility and normal spikelet fertility. Segregation analysis between pollen semi-sterility and RFLP markers on chromosomes 3 and 8 revealed that pollen semi-sterility was associated with RFLP marker G2132 on chromosome 8 (Table 1). At G2132 locus, 60 plants showing normal pollen fertility were homozygous for Taichung 65 alleles, 45 plants showing pollen semi-sterility were heterozygous except for one plant which was homozygous for Taichung 65 alleles. Only heterozygous plants produced semi-sterile pollens. This result indicated that the gene controlling pollen semi-sterility in heterozygous condition was located near the G2132 locus. One pollen semi-sterility plant carrying the Taichung 65 homozygous alleles at G2132 locus was considered as a recombinant between the loci of pollen semi-sterility and G2132. In fact, no homozygous plant for O. glumaepatula alleles at G2132 was observed in BC4F2 population suggesting that the pollen grains carrying O. glumaepatula allele aborted.

So far, three genes controlling pollen sterility, S12, S22(t) and S23(t), in the hybrids of O. sativa and O. glumaepatula have been reported. The chromosomal location of S12 is unknown (Sano 1994). S22(t) is located on the short arm of chromosome 2 (Sobrizal et al. 2000a) and S23(t) is located on the long arm of chromosome 7 (Sobrizal et al. 2000b). Since no gene for F1 pollen sterility on chromosome 8 has been reported, the gene identified in this study was designated as S27(t). Linkage analysis using RFLP markers located near G2132 revealed that S27(t) gene was located between G2132 and L128 (Fig. 2).

This study was supported by Bio-oriented Technology Research Advancement Institution (BRAIN), Japan.


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