QTL Mapping of Basal Root Whorl Number in Common Bean (Phaseolus vulgaris L).

QTL Mapping of Basal Root Whorl Number in Common Bean (Phaseolus vulgaris L).
Magalhaes A. Miguel¹, Kathleen Brown¹, Matthew Blair² and Jonathan Lynch^1*
1Pennsylvania State University, Department of Horticulture, 102 Tyson Building, University Park, PA, 16802, USA
²CIAT, Apartado Aereo 6713, Cali, Colombia.  *Corresponding Author: JPL4@psu.edu

Abstract
Basal root whorl number (BRWN) has been associated with nutrient (especially phosphorus) uptake efficiency in common bean (Phaseolus vulgaris).  Whorls are defined as distinct tiers of basal roots that emerge along the base of hypocotyls, each of which bears up to four basal roots. BWRN ranges from 1 to 4 (rarely 5) whorls among bean cultivars. The objective of this study is to perform a quantitative trait loci (QTL) analysis for BRWN using recombinant inbred lines (RILs) developed from two populations: DOR364xG19833 and G2333xG198339. Phenotypic data on the number of basal root whorls and number of basal roots was obtained from the RILs 3 days after imbibition. QTL analysis for root whorl and root number was performed using composite interval mapping. The results suggest that few QTLs are associated with these traits. We found that almost 25% of the variation for BRWN in DOR364xG19833 and over 58% of the variation for BRWN in G2333 x G19839 RIL populations were controlled by the locus Rwn7.1 on chromosome B7. This high proportion of variance explained by this single locus suggests that this trait is associated with relatively few genes, and that this trait can be used as a criteria for selection of genotypes with better performance in low phosphorus environments.