Determinacy in Common Bean: Duplications, Redundancies, and Multiple Domestications

The domestication syndrome is a suite of morphological and physiological traits that distinguish domesticated plants from their wild progenitors. Investigations into the inheritance of this syndrome have shown that the constituent traits involve sometimes genes with major effects, in addition to quantitative genes. In common bean (Phaseolus vulgaris L.), one of these genes is the fin gene, which leads to an early appearance of an inflorescence at the endings of the main stem and branches. Compared to indeterminate plants, determinate plants have, therefore, a bush growth habit and are early-flowering. We have been able to identify the causal gene for this trait (PvTFL1y), through a combination of large-scale co-segregation, candidate gene approaches based on Arabidopsis flowering time mutations, and transformation. Determinacy appears to have appeared as a de novo mutation and was not part of the standing variation in wild beans. Further analyses have shown that determinacy had multiple origins in different parts of the centers of origin, as suggested by the different mutations in PvTFL1y, including a retrotransposon insertion, a whole-locus deletion, frame shift mutations, and a putative splicing site mutation. Further research is needed to better understand the linked genetic backgrounds of the different mutations,  possible selective sweeps around the PvTFL1y locus, and variation at another duplicate, unlinked locus, PvTFL1z.