• Preliminary report on yield performance of commercial cultivars by the end of year 2 and an expanded report at the end of year 3.
• Release of at least one new germplasm by the end of year 3.
• Quantification of the impact of the slow-wilting trait on seed yield under stress in year 3.
• Quantification of the impact of drought and the slow-wilting trait on seed protein content under stress by the end of year 3.
• Completion of a GWAS study on slow wilting by year 3.
• Backcrossing at least one generation of QTLs into elite varieties using MAS in year 3.
• Quantification of phenotypic data for QTL mapping for slow-wilting by the end of year 3.
• Complete the survey of drought tolerant breeding stock for intrinsic water-use efficiency and report results by the end of year 3. Identify high- and low- intrinsic water-use efficiency progeny from Fiskeby III by the end of year 3.
• Report on the drought threshold for slow-wilting trait advantage by the end of year 3.
• Report on the relations between photosynthesis, leaf water potential, and slow wilting by the end of year 3.
• Assess feasibility of field sites in eastern and western Iowa for conducting drought tolerance research

Updated December 10, 2019:
Yield Potential of Commercial Varieties Under Drought- Identifying and Overcoming Weaknesses via the Public Breeding Pipeline (Year 1 of 3)

IN THIS PROJECT
Farmers need help with drought. This research is designed to help the farmer in 3 phases. 1) Farmers need documented performance data for commercial varieties under drought. We will yield test commercial varieties in multiple states in maturity groups (MG) III through VIII at drought prone sites. Results will aid farmers with variety choices and guide new public-private breeding efforts to fix the drought problem, 2) Farmers need new drought-tolerant breeding stock so that commercial breeding programs can develop better drought-tolerant varieties. The public breeders in this project have a wealth of advanced drought-tolerant materials in their breeding pipeline. New materials will be evaluated and released to commercial breeders based on yield performance under drought. 3) Farmers need basic investigations to support new drought-tolerant variety release. We will conduct QTL mapping, MAS, and, GWAS of field-based slow-wilting and deep-rooting traits. A novel source of superior ‘water use efficiency’ discovered recently in the field (via direct measurements of leaf gas exchange) will be validated. Impact of drought and slow wilting on yield and seed protein will be assessed. Evaluation of drought-tolerant rhizobia will be initiated.

The Current Public Drought-Tolerance Breeding Pipeline Represented by the Project
The breeders in this project from NC, GA, SC, AR, KS, and MO represent most of the applied breeding for drought tolerance in the public sector in the USA. With USB support, we are yield testing more than 1000 new lines each year in addition to QTL mapping, GWAS, and germplasm screening. We have developed appropriate screening sites in all these states and are now developing a site in Iowa. Our previous experience with this project has allowed us to develop a number of new breeding populations that segregate for a wide range of drought traits and alleles. This pipeline, coupled with good field sites and technical knowhow, is the most valuable tool that farmers have for solving the drought problem.

Research Highlights
Private & Public Scientists visit Sandhills, NC Research Station to examine USB’s drought tolerance breeding pipeline. Located near the famous Pinehurst golf courses in NC, this drought-prone research station is perhaps the best in the South for drought tolerance research. This summer, we withstood hurricane Dorian to obtain ideal ‘outdoor laboratory’ conditions for drought research. The sustained drought conditions allowed us to identify and validate many new exceptional drought-tolerant soybean materials in our USB Public Breeding Pipeline. Results generated a lot of excitement in both the private and public sector. Commercial breeders from BASF, Pioneer, and Bayer toured drought-stricken plots and brainstormed about research initiatives with the USB team. University breeders from South Carolina and Georgia also attended. Altogether, 10 visiting scientists toured USB plots in September.

Most commercial varieties appear fast wilting in the Boot Heel of Missouri and Sandhills, NC. USB’s Team Drought evaluated 180 commercial varieties (Group III-V) in MO and 100 in NC (Group-V-VIII) for the slow wilting trait. In each case, only about 10% of the commercial varieties exhibited slow wilting. The paucity of slow-wilting types in the commercial sector highlights the continued need for drought-tolerant varieties in the farmers’ fields.

Two elite group 7 breeding lines confirmed as having a ‘sustained slow-wilting’ trait in NC. The lengthy nature of the 2019 drought at the Sandhills Research Station afforded a rare opportunity to examine our drought-tolerant breeding stocks for ‘sustained slow wilting’ or ‘stronger slow wilting’ as the drought deepened. Dr. Carter identified more than 20 USDA lines which had this trait. Two breeding lines in particular stood out and looked promising under severe drought- N09-13890 and N11-10295. These lines are being considered for germplasm release. The breeding lines have substantial pedigree tracing to drought-tolerant Asian landraces.