Phenotypic Selection for Dormancy Introduced a Set of Adaptive Haplotypes from Weedy into Cultivated Rice

Association of seed dormancy with shattering, awn, and black hull and red pericarp colors enhances survival of wild and weedy species, but challenges the use of dormancy genes in breeding varieties resistant to preharvest sprouting. A phenotypic selection and recurrent backcrossing technique was used to introduce dormancy genes from a wild-like weedy rice to a breeding line to determine their effects and linkage with the other traits. Five generations of phenotypic selection alone for low germination extremes simultaneously retained dormancy alleles at five independent QTLs, including qSD12 (R2>50%), as determined by genome-wide scanning for their main and/or epistatic effects in two BC4F2 populations. Four dormancy loci with moderate to small effects co-located with QTLs/genes for one to three of the associated traits. Multi-locus response to the selection suggests that these dormancy genes are cumulative in effect, as well as networked by epistases, and that the network may have played a "sheltering" role in maintaining intact adaptive haplotypes during the evolution of weeds. Tight linkage may prevent the dormancy genes from being used in breeding programs. The major effect of qSD12 makes it an ideal target for map-based cloning and the best candidate for imparting resistance to preharvest sprouting.

Key Words: Adaptation, Evolution, Invasiveness, Seed dormancy, Weedy rice

This article has been cited by other articles:

				X.-Y. Gu, S. F. Kianian, and M. E. Foley Dormancy Genes From Weedy Rice Respond Divergently to Seed Development Environments Genetics, February 1, 2006; 172(2): 1199 - 1211. [Abstract] [Full Text] [PDF]

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