Molecular marker diversity and hybrid sterility in indica-japonica rice crosses
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Molecular marker diversity and hybrid sterility in indica-japonica rice crosses Zhang, Q., K. D. Liu, G. P. Yang, M. A. Saghai Maroof, C. G. Xu, and Z. Q. Zhou. 1997. Theor. Appl. Genet. 95:112-118. ABSTRACT The partial sterility of hybrids between the indica and japonica rice subspecies is a serious constraint for utilizing inter-subspecific heterosis in hybrid rice breeding. In this study, we investigated the relationship between molecular marker polymorphism and indica-japonica hybrid fertility using a diallel cross made up of 20 rice accessions including 9 indica and 11 japonica varieties. Spikelet fertility of the resulting 190 F1s and their parents was examined in a replicated field trial. Intra-subspecific hybrids showed much higher spikelet fertility than inter-subspecific hybrids, except those involving wide-compatibility varieties. The parents were surveyed for DNA polymorphism using 96 RFLP and 10 SSR markers. The analysis showed that genetic differentiation is extensive between indica and japonica rice. A large number of markers detected highly significant effects on hybrid fertility. The chromosomal locations of those positive markers coincided well with those of known genes for hybrid sterility identified previously. Correlation between hybrid fertility and parental distance was low in both intra- and inter-subspecific crosses. The results suggest that the genetic basis of indica-japonica hybrid sterility is complex, with a large number of loci conditioning indica-japonica hybrid sterility. However, the total amount of the genetic differentiation between the parents contributes very little to the hybrid sterility. Key words diallel cross, hybrid rice, Oryza sativa, restriction fragment length polymorphism (RFLP), simple sequence repeat (SSR)