QTL for yield per plant under water deficit and well-watered conditions and drought susceptibility index in soybean (<i>Glycine max</i> (L.) Merr.)

Drought has historically represented the greatest abiotic stress to adversely affect the stability of soybean (<i>Glycine max</i> (L.) Merr.) yields in non-irrigated field conditions. To investigate the genetic basis underlying drought tolerance in soybean, we screened the seed yield per plant (YP) in a natural diversity panel of 149 accessions under both water deficit (drought-stressed; YP-S) and well-watered (full irrigation; YP-W) conditions in field and greenhouse trials and calculated a drought susceptibility index (DSI) based on the differences in yield between treatments within each accession. A total of 19 quantitative trait loci (QTLs) were identified: eight were significantly associated with YP-W, 10 were associated with YP-S, 2 were associated with DSI and one QTL was associated with both YP-S and DSI. We then compared QTLs identified here with previously reported markers and found that these loci were located in regions associated with yield-related and other agronomic traits. In particular, YP-S-associated single nucleotide polymorphism (SNP) ss246509299 in chromosome (Chr.) 8, and YP-W-associated ss249310678 on Chr. 17 were both previously correlated with canopy wilt. Eight significant QTLs were located within eight genes. <i>Glyma.18g092200</i>, contained ss249600231 and annotated as <i>GmWRKY168</i>, is reportedly responsive to cadmium. This study helps to resolve which loci contribute to yield under drought stress in soybean, and can potentially serve as markers for selection of elite, high-yield and drought tolerant varieties.