Mapping of Quantitative Trait Loci (QTL) Related to Drought Tolerance in Common Bean (Phaseolus vulgaris L.) Using F2 Population from (KATB1 Χ GLP2)

Many of the common bean growing regions around the world are prone to drought stress, making drought the major challenge to production and yield stability in rainfed environments. Mapping of yield-associated loci under drought stress will offer a better understanding of the genetics of drought tolerance to the plant breeders and therefore, will accelerate the selection of drought-tolerant crop varieties through marker-assisted selection (MAS). The current study reports the identification of quantitative trait loci (QTL) linked to physiological, phenological, yield and yield-related traits using 120 F2 population derived from a cross between two common bean genotypes, KAT B1 (drought tolerant) and GLP2 (drought susceptible) evaluated under drought stress and well-watered conditions. The research was conducted at the Agricultural and Mechanization Institute, Machakos, Kenya. The F2 population showed significant variation in traits under drought stress.  From the 374 polymorphic SNP markers surveyed, 20 genomic regions were identified for various traits under drought stress, individually explaining 2.6 to 21.3% of phenotypic variation. The number of QTLs identified per trait were: 2-grain/seed yield (GY); 1-number of branches (NBP); 2-stem biomass (SB); 1-leaf biomass (LB); 1-pod biomass (PB); 3-days to flowering; 2-days to maturity (DM); 4- number of pods per plant (NPP); 1-seed weight (SW); 2-stomatal conductance (SMTL) and 1-leaf water potential (LWP). QTLs for number of pods per plant, number of grains/seeds per pod, days to flowering, leaf biomass and stem biomass were found co-locating with QTLs for grain yield on chromosome Pv02 under drought stress treatment. The cumulative effects of these QTLs on chromosomes 2 resulted in higher grain/seed yield. This study has provided information on QTLs in common bean that could be used in selection purposes for grain yield under drought conditions.