| Drought is a major constraint limiting dry bean (Phaseolus vulgaris L.) yield worldwide. Some lines express tolerance but the mechanisms are not well understood. We sought to: i) identify quantitative trait loci (QTL) conditioning drought tolerance in a bi-parental mapping population, ii) use selective phenotyping to characterize important phenotypic traits associated with drought tolerance, and iii) perform association mapping to discover novel QTL conditioning drought tolerance. We tested 140 RILs (Buster/Roza) for yield under multiple stress (MS) and terminal drought (DS). A genetic linkage map (953 cM) was generated using SNP markers. Two major QTL influencing seed yield (SY) were observed. The SY1.1 QTL explained up to 37% ( R2) of the phenotypic variance for seed yield under MS and was consistently expressed each year. The SY2.1 QTL was detected under DS (33%) and MS (23%). For extensive phenotyping, 40 lines from the original mapping population were evaluated for 19 traits. The phenotypic extremes helped to sort through traits relevant to stress response in the population and verified the effect of two major QTL for yield response under terminal drought. Of all traits examined, pod wall ratio (PW), biomass (BM) and greenness (NDVI) were most associated with SY under stress followed by phenology. Phenotypic extremes validated QTL discovered with whole RIL population and identified new QTL for PW1.2BR and NDVI 1.1BR on chromosome Pv01. A panel of 160 lines and cultivars from Durango race was tested under MS and DS for one year and genotyped with 5398 SNPs. The PW, BM, and phenology traits were all correlated with SY under DS. Association mapping revealed novel QTL for days to flowering (DF), plant height (PH), seed weight (SW), BM, PW, and SY under MS and DF, BM, SW, and geometric mean under DS. This study offers QTL influencing yield under multiple stress environments and identification of traits associated with drought tolerance. |
