Underground Imprints of Selection: Transition of Various Root Architectural Traits during Domestication of Common Bean (Phaseolus vulgaris L.)

Continuous selection for the most desirable phenotypes from wild populations during domestication changes allele frequencies at specific targeted loci. Genomic regions subjected to selection have been identified in various domestication studies, which have further led to the discovery of major genes that control domestication syndrome traits. However, previous analyses of domestication have mainly focused on the above-ground plant organs, while root traits have escaped direct scrutiny due to their underground nature. We hypothesized that domestication-associated changes in root traits are due to selection for above ground traits that also affect roots, and indirect selection for root traits that improve above ground plant performance. To test this hypothesis, we have performed QTL analyses using a RI population of the common bean (Phaseolus vulgaris) derived from the cross [G19833 (landrace) X G23419 (wild accession)]; parents are of Andean origin.  A SNP-based linkage map was constructed for this purpose using the GBS method. Time series root images were collected using a novel 2-Dimensional phenotyping platform. Approximately 4200 root images were analyzed for various dynamic root growth and architectural traits. Our analysis has revealed several independent QTL that control various aspects of root growth and architecture. The effect of seed size, the main target of domestication, on early root growth and development is in agreement with part of our hypothesis. In summary, we have identified a few genomic regions associated with QTL controlling differences between the landrace and the wild parent. These results provide a platform to identify candidate genes involved in domestication