Identification of QTL associated with drought tolerance in Andean common bean

Summary

Drought stress is becoming one of the most important abiotic factors limiting productivity of common bean (Phaseolus vulgaris L.) globally. The objective of this study was to conduct a quantitative trait loci (QTL) analysis of drought tolerance in a recombinant inbred line (RIL) mapping population genotyped using single nucleotide polymorphism (SNP) markers. The RIL population was developed by crossing Portillo × Red Hawk, two Andean bean genotypes contrasting in reaction to drought stress and evaluated at two locations in Uganda for two seasons under drought stress (DS) and non-stress (NS) conditions. Eighteen significant QTL signals were identified for phenology, yield component, and partitioning traits on chromosomes Pv01, Pv02, Pv03, Pv04, Pv06, and Pv11 under DS and NS conditions. Quantitative trait loci for seed yield per plant (SY) were detected on Pv01, Pv02, Pv03, Pv04, and Pv06 under DS conditions. Co-localized QTL signals for pod weight per plant and SY were identified under DS on Pv01 (45.15 Mb) and on Pv02 (0.12 Mb), for phenology and SY on Pv03 near marker ss715639424 (40.16 Mb), and for SY and harvest index on Pv06 (17.92 Mb). Two candidate genes related to flowering were identified within a 35-kb region from the ss715639424 marker on Pv03. Gene Phvul.003G189100 (30.3 kb) encodes “AGAMOUS-LIKE 65 (AGL65)”, which is essential for pollen development, and gene Phvul.003G189300 (17.9 kb) encodes “CYCLING DOF FACTOR 3 (CDF3)”, which regulates flowering time. The same SY QTL, SY3.3^PR on Pv03, was previously detected in Mesoamerican germplasm and could be used through marker-assisted breeding to improve SY of Andean beans grown under DS.