UC Davis

Key message

A common bean shattering-resistance allele of PvPdh1 reduces pod twists during dehiscence, shows dominance that varies by phenotyping method, is part of a selective sweep, and can be introgressed using CAPS markers. Some varieties of common bean (Phaseolus vulgaris L.) suffer from pod shattering, which can severely reduce yields, especially in arid conditions. The PvPdh1 locus on chromosome Pv03 has recently been described as a major locus controlling pod shattering in common bean and could be used to mitigate pod shattering in the future. Despite this, the role of a possible second locus on chromosome Pv08 remains unclear and patterns of dominance and epistasis between alleles of these genes have not been resolved. This information will be vital for efficient selection to decrease pod shattering. Further, the genetic diversity around the PvPdh1 gene has not yet been thoroughly explored, and there are not yet genetic screens that can be used to evaluate pod shattering in segregating populations. Here, we have developed a recombinant inbred population to determine the roles of genes implicated in pod shattering and evaluate the patterns of dominance among the relevant alleles. Our results suggest that a PvPdh1 allele reduces pod valve twisting, and its dominance varies by phenotyping method. This allele is the only genetic variant that provides environmentally stable and widespread resistance to pod shattering in Middle American common beans grown for grain. Further analyses identified a selective sweep around PvPdh1 with greater nucleotide diversity in individuals with the ancestral, shattering-susceptible allele. Finally, we developed simple, effective CAPS markers to facilitate the introgression of PvPdh1 into new varieties of common bean. These genetic resources will be critical for improving the aridity resilience of a major global staple.