Objective 1: Physiological mechanisms of drought tolerance.
• Publish peer-reviewed manuscripts on novel insights into the plasticity of the primary physiological traits (WUE, CT, CW, and NDFA), and the implications associated with differences in plasticity relative to performance in different environmental conditions.
• Establish the extent and types of interrelationships that exist among the primary drought-tolerance stress traits.
• Publish manuscripts documenting underlying physiological mechanisms that confer genotypic differences in CW, CT, WUE, and NDFA.
• Identify putative new mechanisms for soybean drought tolerance including hydraulic conductivity and leaf anatomical differences.

Objective 2: Identification and confirmation of putative drought tolerance loci.
• Communicate results of QTL mapping of WUE, CT, CW, and NDFA to the soybean research community through presentations at meetings, reports, and publications.
• Identify novel loci putatively associated with plasticity of each primary physiological trait and communicate that information through presentations and publications.
• Share identity and locations of confirmed genes (QTLs) for CW, CT, WUE, and NDFA to the soybean community through meetings, reports, and publications.

Objective 3: Germplasm and population development.
For current F6-derived WUE lines (PI 567201D x DS25-4):
• Document results of 2018 irrigated yield trials comparing high WUE lines versus low WUE lines through scientific presentations, reports, and publications by 2019.
• Identify the best WUE lines based on irrigated and non-irrigated trials in 2019/2020 and enter those lines for Regional Uniform testing by 2020.
• Determine the “realized heritability” of the WUE trait based on 5 years of pedigree selection for WUE and 3 years of replicated testing of the resulting lines in multiple states (AR, AZ, MO, and MS) by 2020.

Updated December 10, 2019:
By drawing upon USB’s previous investment for genotyping the USDA germplasm collection, we have been able to combine that genomic information with measurements we have made on 373 accessions for four critical traits associated with drought tolerance: canopy wilting, canopy temperature, water use efficiency (using the ration of carbon-13 to carbon-12, d13C), and N2 fixation. The combination of the genetic information with our measurements has allowed us to identify multiple DNA regions associated with each of these traits and that can be used to transfer these traits to high-yielding lines. This combined information has also allowed us to delve deeply into understanding how these four traits function and how these traits are impacted in different environments. In 2019, we were successful in combining germplasm selected for slow canopy wilting with cool canopy temperature and for d13C with N2 fixation; we are poised in 2020 to combine all four of these traits into a single genetic background. For the d13C trait, we have advanced lines that will be evaluated in multi-state yield tests in 2020.