Mapping QTLs for defective female gametophyte development in an inter-subspecific cross in Oryza sativa L.

The embryo-sac is an essential structure for angiosperm reproduction. The cytological and genetic characterization of embryo-sac sterility was examined in a cross between Oryza sativa ssp. indica cv.. ZYQ8 and ssp. Japonica cultivar, JX17. The arrest of embryo-sac development was manifested following meiosis in the F-1 hybrid. When the megaspore carried the lethal genotype, the nucleus either failed to divide or divided only once, and the immature embryo-sac degenerated. Abortion of the embryo-sac in the indica-japonica hybrid background was not observed in their original parents, and an effect of cytoplasmic gene(s) on embryo-sac sterility in the reciprocal F-1 hybrids was not detected. Using a rice molecular linkage map based on a doubled haloid (DH) population from the cross of ZYQ8/JX17, we mapped quantitative trait loci (QTLs) for the defective development of the female gametophyte in backcross progenies from the DH lines. The result demonstrated that a polygenic system is involved in both megagametogenesis and postzygotic isolation in inter-subspecific: hybrid rice.