GENETIC-CONTROL OF THE DOMESTICATION SYNDROME IN COMMON BEAN

The marked phenotypic differences for morphological and physiological traits that distinguish wild progenitors and cultivated descendants (' 'the domestication syndrome'') and the lack of information about their genetic control have limited the utilization of wild germplasm for cr op involvement. This study was conducted to assess the genetic control of the domestication syndrome In common bean (Phaseolus vulgaris L.). A recombinant inbred population resulting from a cross between a wild and a cultivated common bean was subjected to molecular linkage mappi ng and evaluation in short-day and long-day environments. We show that the genetic control of this syndrome in common bean involves genes th at can have a large effect (>25-30%) and account for a substantial par t of the phenotypic variation observed (>40-50%). The distribution of domestication syndrome genes appears to be concentrations in three gen omic regions with a major effect on the syndrome, one of which greatly affects growth habit and phenology, the other seed dispersal and dorm ancy, and a third, the size of fruit and seed, all of which are import ant traits in determining adaptation to a cultivated environment. Wher eas the influence of genetic background and environment on the express ion of some traits will have to be further analyzed, our results sugge st, however, that domestication of common bean could have proceeded ra pidly (provided that genetic diversity and selection intensity were hi gh) and that evolution can proceed through changes involving a few gen es with large effect rather than through a gradual accumulation of cha nges coded by changes with small effects. They also suggest that adapt ation to rapidly changing environmental conditions may involve genes w ith large phenotypic effects. The information presented here should le ad to marker-assisted selection experiments of introgression of additi onal genetic diversity into the cultivated common bean gene pool.