13. Molecular mapping of a new pollen killer gene S29(t) on chromosome 2 in Oryza glaberrima

F.Y. HU, P. XU, X.N. DENG, J.W. ZHOU, J. LI and D.Y. TAO

Food Crops Research Institute, Yunnan Academy of Agriculture Sciences, Kunming 650205, China

Oryza glaberrima is a valuable source of genes for O. sativa improvement (Jones et al. 1997). However, a series of genetic loci that induce interspecific hybrid sterility between these cultivated species has been identified in O. glaberrima. The series includes gamete eliminator S1 and pollen killers S3, S18, S19, S20 and S21(Doi et al. 1998, 1999; Sano et al. 1983, 1986; Taguchi et al. 1999). These loci are major obstructions to the introgression of favorable gene/traits from O. glaberrima into O. sativa. An understanding of these and other sterility genes is necessary to be able to overcome crossing barriers and thus open the door for mining useful genes from O. glaberrima. In this study, we identified a new pollen killer S29(t)

and mapped it on chromosome 2 by SSR markers.

A near-isogenic line WAB450-6, derived from interspecific hybrid of O. sativa and O. glaberrima, induced frequent abortion of pollen grains but gave completely fertile spikelets when hybridized with its recurrent parent, WAB56-104, an upland japonica from WARDA (Tao et al. 2002). Semi-sterile individuals were backcrossed as female parents to WAB56-104, and a semi-sterile individual of BC2F1 was selected to produce a BC2F2 population with 142 plants in the winter crop season (November-April) in Hainan, China, in 2004. The population showed a clear-cut bimodal distribution for pollen fertility (Fig. 1), indicating a single gene controlling sterility. This BC2F2 population was employed in segregation analysis for the sterility gene and 216 SSR markers distributed among the 12 chromosomes. The sterility gene was linked with the SSR marker RM7033 on chromosome 2. Thus, a molecular linkage map in this region was constructed for mapping the male sterile gene from WAB450-6, and this gene was mapped to the interval between markers RM423 (1.3 cM) and RM7033 (1.1 cM) on chromosome 2 (Fig. 2). The fact that none of the sterility genes previously reported from O. glaberrima was on chromosome 2 suggests that this gene is a new pollen killer, tentatively designated as S29(t). Fine mapping of this gene using a bigger advanced backcross population is ongoing.

This study was supported by grants from Yunnan Natural Science Foundation of China (2002C0009Z).


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