Flooding for periods lasting as short as two days has been shown to reduce yields by as much as 27% during the early vegetative or early reproductive growth stages. Heavy rain in the early summer could make standing water in the field for several days, which would significantly damage farmers' fields by causing seedling emergence and establishment problems and impair/injure young soybean plants. In recent years, increase of floods from intense precipitation events was observed on a larger scale than in previous decades in the North central areas.
The best strategy to protect farmers from the ravages of flooding is release of new flood-tolerant soybean varieties and their integration into flood-tolerance management systems. PI Nguyen and co-PI Shannon have been actively researching the genetic basis of flood tolerance in soybean. With the proposed partnership among the University of Missouri, the University of Minnesota, and Iowa State University to work on this topic and prior work by members of this team, this NSCRP project is dedicated to solving this problem by taking advantage of the most active and successful breeding pipelines in the world for the release of flood-tolerant varieties.
Drought has become a significant problem that can affect farmers anywhere in the US. Drought stress can not only reduce yield, but also its components, oil, and protein as well as physiological processes such as nitrogen fixation. Drought resiliency in soybean has a short history of research and publication, beginning in the late 1980’s. Slow wilting, which was predicted to improve yield 75-85% under drought stress through a simulation model analysis, is a famous and reliable drought tolerance trait identified so far in soybean research and breeding community. Soybean breeders including Dr. Grover Shannon in this proposal have been developing drought-resilient germplasm and varieties. However, most of the breeding work has been conducted in late maturity groups (MGs) (late IV to VII). These developed drought tolerance traits need to be incorporated into the early MGs (0 to early IV) suitable for the North Central region of the US.
Thus, we propose to characterize soybean germplasm for early season flood tolerance to identify tolerant genetic resources and molecular markers for breeding applications and to develop new soybean varieties with drought and flood tolerance in maturity groups 0 to IV. The expected results will support sustainable soybean production and stabilize farm income in face of the increasing threat of flooding and drought stress in the North Central region.

1. Characterize soybean germplasm for early season flood tolerance at seedling establishment and early vegetative growth stages and identify tolerant genetic resources and molecular markers for breeding applications.
2. Develop flood tolerant germplasm and varieties in early maturity groups (0 to IV) for north central region by introgression of tolerance traits from the already developed genetic resource in later maturity groups (late IV and V).
3. Pyramid drought tolerance with flood tolerance in early maturity groups (0 to IV) soybeans for the north central region.

New genetic resources (lines and genes) for early maturity soybeans (0 to early IV); DNA markers for molecular breeding; Improved high-yielding and germplasm with stable flood and drought tolerance (>15 bu/ac advantage under stresses).

Updated April 7, 2023:
This project aims to (1) characterize soybean germplasm for early season flood tolerance at the seedling establishment and early vegetative growth stages and identify tolerant genetic resources and molecular markers for breeding applications, and (2) develop flood and drought tolerant germplasm and varieties in maturity groups 0 to IV for the north central region by introgression of tolerance traits from the already developed genetic resource in late maturity groups (late IV and early V).
During the first year of the project, we screened a soybean core set (300 diverse lines which were sequenced) for tolerance during seedling emergence and the early vegetative stages (separately) using soil beds in the greenhouse of the University of Missouri.
Significant phenotypic variation in flood tolerance was observed. We selected 60 lines contrasting in flood tolerance level for further confirmation in the greenhouse in April 2023. We will further select the 10 most tolerant and 10 most sensitive lines for field confirmation at 4 locations this summer.
Genome-wide association studies (GWAS) will be performed to identify loci associated with flooding tolerance. DNA makers for the tolerance genes/QTL will be designed and developed for marker-assisted selection. These results are expected to be updated in our next report.
Meanwhile, we validated our DNA markers for gene pyramiding. We are ready to genotype the breeders’ crossing and backcrossing materials starting April 2023.
Soybean breeders at the University of Missouri, Kansas State University, Iowa State University, and the University of Minnesota have successfully developed backcross and forward breeding populations to deliver results for objective 2.

View uploaded report

The technology developed from this project, including germplasm, genes, markers, screen methods, and management strategies will help the research community, private and public breeders, and producers in dealing with flooding and drought stress. We are aiming to improve the yield advantage of 10 to 20 bu/acre under flooding and drought stress in the new lines without compromising yield potential under normal non-stress condition. All those protected bushels will directly transform into the farmers’ profits.

Five soybean germplasm lines from the exotic genetic pools (MG 0 to III) are identified for early-season flood tolerance in 2023; Two major QTL/candidate genes are identified for flood tolerance and the associated DNA markers will be developed for marker-assisted selection in 2023; Incorporation of flood and drought tolerance traits and genes into the early maturity group varieties using the developed DNA markers by the end of the project in 2025; Two advanced flood/drought tolerant and high yielding soybean germplasm lines are transferred to industry and other public plant breeders and used as parental stock to develop commercial varieties by 2025.