Genetics of hybrid sterility and hybrid breakdown in an interspecific rice (Oryza sativa L.) population
1996
Li, Z. | Pinson, S.R.M. | Paterson, A.H. | Park, W.D. | Stansel, J.W.
Hybrid sterility (F1 sterility) and hybrid breakdown (sterility and weakness of the F2 and later generations) in crosses within cultivated rice (Oryza sativa L.) are common and genetically complicated. We used a restriction fragment length polymorphism linkage map and F4 progeny testing to investigate hybrid sterility and hybrid breakdown in an intersubspecific cross between a "widely compatible" japonica variety, Lemont, from the southern United States and an indica variety, Teqing, from China. Our results imply different genetic mechanisms in hybrid sterility and hybrid breakdown, respectively. Hybrid sterility appeared to be due to the breakdown (by crossing over) of a number of putative differentiated "supergenes" in the rice genome, which may reflect cryptic structural rearrangements. The cytoplasmic genome had a large effect on fertility of both male and female gametes in the F1 hybrids. There appeared a pair of putative complementary genes which had a very large effect on sterility and behaved like wide compatibility genes. We speculate that this pair of genes and the "gamete eliminator" (S1) or "egg killer" (S-5) may influence the phenotypic effects of presumed "supergenes" in hybrids. Hybrid breakdown appeared to be due to the breakdown of coadapted indica and japonica gene complexes by random assortment of large numbers of unlinked complementary quantitative trait-modifying factors throughout the genome. These proposed mechanisms may partly account for the complicated nature of the post-reproductive barriers in rice
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