Plant & Animal Genome VI Conference

W83

INFLUENCE OF EPISTASIS AND DIVERSE EVOLUTION ON WIDE CROSSES OF COMMON BEAN

Dept. of Agronomy and Range Science, University of California, Davis, One Shields Ave. Davis, CA 95616

The germplasm of cultivated common bean (Phaseolus vulgaris L.) exhibits a lower level of genetic diversity within each of two geographical gene pools (Mesoamerican and Andean) compared to that of the respective wild ancestors. Hybridizations between these two gene pools potentially provide a source of additional genetic diversity, but their progenies are characterized by phenotypic abnormalities and reduced productivity. We conducted replicated field trials of two recombinant inbred populations (RIPs) resulting from Mesoamerican x Andean crosses. The agronomic performance of each recombinant inbred line (RIL) in the two RIPS was assessed for traits associated with robustness (biomass growth rate), earliness (days to maturity), fertility (harvest index), and agronomic productivity (economic growth rate). We performed QTL analyses in order to estimate the magnitude and the genomic locations of the genes conditioning these traits in Mesoamerican x Andean derived populations, and found evidence for epistatic interactions between loci affecting these traits. Co-localization of QTLs affecting both economic growth rate and other traits was used to speculate the pleiotropic effects genes. The lack of a clear pattern for digenic epistatic interactions (parental type versus recombinant type superiority) suggests that there is poor evidence for overriding effects of coadapted gene complexes from the genetically divergent parents conditioning productivity in their progeny. These results are discussed in relation to known patterns of genetic diversity within the species, the historical reticence of breeders to employ inter-gene pool crosses, and the prospects for using marker assisted selection to improve breeding programs.