Location: Soybean and Nitrogen Fixation Research
Project Number: 6070-21220-070-037-R
Project Type: Reimbursable Cooperative Agreement
Start Date: Oct 1, 2023
End Date: Sep 30, 2024
Objective:
Flooding stress can give rise to poor emergence and plant stand problems early in the season and plant damages/injuries later in the season. Flooding and waterlogging (chronically wet, but no standing water) can cause slow growth, poor leaf color, spindly plants, and result in ~40% yield loss. Due to changes occurring in the climate, there has been an increase in the occurrence of heavy rainfalls and saturated soil conditions in many regions of US soybean production. By 2030, an alarming 30% increase in heavy precipitation events is expected. Flooding stress represents a major production constraint that farmers must deal with each year. Therefore, we aim to identify flood-tolerant soybean breeding resources and commercial varieties and develop flood-tolerant soybean germplasm and varieties.
Objectives to which ARS investigator will contribute:
1. Evaluate flood tolerance of commercial varieties in maturity groups (MG) V through VIII.
2. Develop and release high yielding and flood tolerant germplasm to support commercial variety development.
3. Identify new flood tolerant genetic resources by screening wild soybean accessions, which will increase genetic diversity and improve flood tolerance.
Approach:
Objective 1: Commercial varieties will be selected in conjunction with the local North Carolina Official Variety Testing (OVT) Program and private breeders. Lines will be evaluated for flood stress at early reproductive and vegetative growth stages in replicated field trials. Before flooding berms will be constructed around appropriate blocks using a tractor-mounted inverted disc plow to produce walls of 0.75 m height and 1 m width. Flooding will occur for 7 days and then the water will be released. At 7 and 14 days after flooding has been released all varieties will be evaluated on a scale from 0-9, with 0 being no damage and 9 being severe damage and plan death has occurred.
Objective 2: Newly identified promising flood-tolerant genetic resources will be used to develop high yielding, flood tolerant breeding lines using conventional breeding methods. Hybrid seed will be developed in the summer of 2023 and 2024 from more than 5 unique flood tolerance x high yield crosses and hybrid (F1) plants will be grown in the USDA winter nursery in Puerto Rico the following winter. In 2024, F2 plants will be grown in NC and advanced using the modified single seed descent breeding method. Newly developed flood tolerant lines will be tested for flood tolerance at V4 and R1 growth stages, similar to the procedure in objective 1. In addition, yield evaluation of selected flood tolerant lines (15 to 20 lines), subjected to flood and non-flooded field conditions will be conducted in NC in 2024.
Objective 3: Flooding injury scores will be collected for a diverse set of 300 maturity group (MG) IV-V lines and a new RIL population derived from an elite x wild soybean cross developed to potentially identify a new tolerance source will be evaluated using the approach mentioned in objective 1. In addition, previously identified flood tolerant wild soybean accessions PI407220 (MG V), PI597459C (MG III), PI424082 (MG V), and PI378683 (MGVI) will be crossed with elite cultivar NC-Dunphy. Selection for flood tolerance trials will commence in 2023 and continue in 2024. Testing will include flood tolerant and sensitive checks, advanced USDA breeding lines and newly identified flood tolerant lines for comparison.
