Genome-wide Association Analysis of Carbon Isotope and Oxygen Isotope Ratios in Diverse Soybean [Glycine max (L.) Merr.] Genotypes

Drought stress is a major factor limiting soybean [Glycine max (L.) Merr.] yield. High water use efficiency (WUE) contributes to crop productivity under drought, but increased WUE is often associated with a decrease in transpiration (T), which is often accompanied by a decrease in biomass. This interdependence of T and biomass production is a major constraint in selection for high WUE by breeding programs. Measurement of genetic variability in WUE and T through carbon isotope ratio () and oxygen isotope ratio (), respectively, could be important in identifying genotypes with high WUE that also have relatively high T, and hence, high rate of biomass production. The study’s objective was to identify SNP markers associated with whole-plant biomass  and. A diverse collection of 373 soybean genotypes were characterized for  and  in four field environments (two years and two locations). A genome-wide association analysis were performed using 31,260 SNPs with a minor allele frequency (MAF) ≥ 5% to identify SNPs associated with  and . Several environment-specific SNPs were identified by using different statistical models, and 187 and 50 SNPs showed a significant association with  and, respectively, for at least two of the environments present in all models. Putative loci with multiple SNPs, that were located close to each other, were identified on chromosomes 2, 5, 13, 15 and 17, and on chromosome 4 and 6 for   and  respectively. These markers may represent an important resource for pyramiding favorable alleles for identifying drought-tolerant genotypes.