23. Mapping of F1 pollen semi-sterility gene found in backcross progeny of Oryza sativa L. and Oryza glumaepatula Steud.

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

Sobrizal et al. (1999) developed the Oryza glumaepatula introgression lines in the background of O. sativa cv. Taichung 65. During the process of development, we observed that the pollen semi-sterile plants segregated in a BC4F1 population. To study the inheritance of this trait, a BC4F1 plant showing pollen semi-sterility was backcrossed with Taichung 65. The BC4F1 plant used for backcrossing was found to have retained O. glumaepatula chromosomal segments on chromosomes 4, 7 and 9, when the BC4F1 generation of O. glumaepatula introgression lines was genotyped using 106 RFLP markers scattered in 12 chromosomes (Sobrizal et al. 1999). One hundred and four BC5F1 plants were grown and the pollen fertility was studied. There were 50 normal and 54 semisterile plants (Fig. 1). This segregation ratio agreed with monogenic segregation ratio (1:1), indicating that the F1 semi-sterility was controlled by a single gene. Furthermore,

linkage analysis was carried out using RFLP markers located on chromosomes 4, 7 and 9. The result suggested that the gene controlling F1 pollen semi-sterility was located between RFLP markers R1789 and C213 on chromosome 7 and co-segregated with RFLP marker C1340 (Fig. 2).

So far, two genes controlling pollen sterility, S12 and S22(t), in the hybrids of O. sativa and O. glumaepatula have been reported. The chromosomal location of S12 is unknown (Sano 1994), whereas S22 is located on the short arm of chromosome 2 (Sobrizal et al. 2000). Doi et al. (1999) reported that the F1 pollen semi-sterility gene S21, identified in backcross progeny of O. sativa and O. glaberrima is also tightly linked with RFLP marker C1340 on chromosome 7. There is high possibility that S21 is allelic to the F1 pollen semi-sterility gene found in this study. However, the gene identified in this study was tentatively designated as S23(t) until the allelic relationship is verified.

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


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