Genomic Regions Controlling Root Growth and Architectural Traits Associated With Domestication Of Common Bean (Phaseolus vulgaris L.).

Selection for the most desirable alleles and consequent changes in allele frequencies has accompanied the phenotypic alterations between wild and domesticated populations of various crop plants. These alterations include significant structural and physiological changes. Genetic analysis of various domestication-associated traits has detected genomic regions subjected to selection, and has also led to the identification of major genes that regulate those traits. However, previous analyses of domestication have mainly considered the above-ground plant organs, while root traits have been largely neglected because of underground nature of this organ. This problem was further complicated by time consuming and inaccurate methods of phenotyping root traits by digging and washing roots from the soil. However, it is very likely that changes in root growth and architecture might have happened because selection for particular shoot traits can lead to inadvertent selection for root traits as these organs need to operate in functional equilibrium with each other. Thus, we hypothesized that domestication of the common bean brought about changes in root traits controlled by two types of genes, one that controls root growth only, while the other regulates resource allocation to maintain a functional balance between root and shoot. We have performed a QTL analysis using a recombinant inbred population derived from a cross between a landrace (G19833) and a wild accession (G23419), both from the Andean gene pool.  A SNP-based linkage map was constructed using the genotyping-by-sequencing approach. Time series root images were collected using a novel 2-Dimensional phenotyping platform. Approximately 4000 root images were analyzed for various root growth and architectural traits. QTL analysis has revealed a number of loci that control various aspects of root growth and architecture. Genomic regions identified were clustered along the genome. Identified QTL regions will be searched for candidate genes which will be tested to determine their role in domestication.