Variability of root traits, seed size and tolerance to low soil phosphorus in common bean (Phaseolus vulgaris L.)

Common bean is an important food and cash crop, but its seed yield productivity is constrained by the soil phosphorus (soil-P) deficiency among other factors. This study was implemented to determine variability of root traits and seed size of 14 bean genotypes, and identify genotypes with tolerance to low soil-P. A pot experiment was laid out in split-plot design with two replicates. Highly significant (P < 0.01) mean square differences were observed among the genotypes and the genotype × soil-P interactions for all the root traits and seed size. Genotypes BFS-29, USRM-20 and SEF-15 all of Meso-American origin had the lowest values for seed size reduction rate and low fertility susceptibility index and were, therefore, considered tolerant to low soil-P. Cumulatively PC-1 and PC-2 accounted for about 99% of the total variability and were both highly correlated with Hypocotyl Root Length (HRL). PC-2 was also highly correlated with basal root whorl number, basal root growth angle, basal root length and tap root diameter. Quadrant-3 comprised of genotypes USRM-20, SEF-15, BFS-29 and SAB-560 that were tolerant to low soil-P and were characterized with longer basal roots, large tap root diameter, and high seed size. The tolerant genotypes need to be tested on a large scale, conserved and could be utilized in bean improvement programs for low soil-P tolerance.