Location: Grain Legume Genetics Physiology Research
2021 Annual Report
Objectives
Objective 1: Determine yield response and identify yield limiting factors of edible legume germplasm when grown under abiotic stress and managed using different production systems.
Sub-objective 1A: Assess inoculant effects on winter survivability, root rhizobial biodiversity, nitrogen fixing capacities, and yield of direct-seeded advanced edible winter pea (Pisum sativum L.) cultivars in a winter wheat crop rotation.
Sub-objective 1B: Identify novel pea germplasm with cold and drought tolerance, in the presence or absence of Rhizobium, to improve food-grade winter pea production across different agro-ecological environments.
Objective 2: Enhance G x E x M to develop biotic stress-resilient edible legume cropping systems that improve sustainable production.
Sub-objective 2A: Assess the G x E x M interactions of multiple bean genotypes to white mold under different tillage, fertilization and irrigation practices.
Sub-objective 2B: Identify and determine Fusarium root rot genetic resistance and the effect of seed treatments on root rot severity, rhizobial formation and winter survival in winter pea under different agro-ecological environments.
Approach
Sub-objective 1A:
Hypothesis: Winter peas will interact favorably with Rhizobium inoculants to improve winter survival, seed nutritional qualities, yield, and soil health.
Approach: Ten food-grade, cold tolerant, winter peas will be grown at two locations. Presence of Rhizobium inoculant on emergence, root nodulation, chlorophyll content, plant height, root/shoot dry weight, root disease severity, rhizobial diversity, soil nitrogen, seed composition, and seed yield/quality over multiple years will be evaluated.
Sub-objective 1B:
Goal: Identify novel pea germplasm from worldwide collections useful for improving cold and drought tolerance in food-grade winter pea cultivars.
Approach: Pea lines evaluated will be screened for cold tolerance (CT) under natural conditions. Lines with CT will be evaluated for drought and disease tolerance in seven rainfall zones. The five highest yielding lines with the best cold and drought tolerance across rainfall zones will be grown at the three lowest rainfall zones and presence/absence of Rhizobium inoculant on these lines evaluated.
Sub-objective 2A:
Goal: Identify G x E x M interactions that improve control of white mold disease of bean.
Approach: Three tillage (conventional, minimum, and no-till) treatments will be evaluated in alternating strips across a field. Two irrigation treatments, 80 and 100 percent evapotranspiration, will be imposed at flowering through maturity. Eight lines will be assessed across tillage x irrigation combinations. Traits measured will include: emergence, stand vigor, flowering date, canopy porosity, lodging, canopy height, normalized difference vegetation index, canopy coverage, canopy temperature, disease incidence/severity, above ground biomass, yield, and seed weight.
Sub-objective 2B:
Goal: Identify genetic resistance and fungicidal seed treatment combinations effective against Fusarium root rot (FRR) species impacting winter pea across different precipitation zones.
Approach: Twelve winter pea fields from six precipitation zones in Washington will be assessed for FRR at four growth stages and species identified. Pea lines from the Pisum Core Collection and cold-tolerant lines identified in Sub-objective 1B will be screened for resistance to the two major FRR species and association and bi-parental mapping populations used to determine quantitative trait loci associated with the resistance. Four winter pea lines with the best CT, resistance to FRR, and yield will be planted in three precipitation zones in Washington and treated with four fungicidal seed treatments to determine best management practices for FRR.
Progress Report
In support of Sub-objective 1A, the impact of residual nitrogen and other soil factors generated by 10 fall-sown “winter” pea varieties were evaluated by planting winter wheat in soil previously cropped with the 10 winter pea varieties at the University of Idaho’s Parker Farm in Moscow, Idaho. The impact of each pea line on the mean wheat plant height, number of tillers, yield and wheat protein content was determined. Although winter peas have been sporadically grown in the United States for more than 20 years, none of these peas have been considered “food grade”, or acceptable for human diets, and were only used as animal feed. During this year the research unit released three new food grade winter pea varieties, “USDA-MiCa”, “USDA-Dint”, and “USDA-Klondike”. These are the first food grade winter pea varieties released by the USDA. The initial commercial plantings of all three varieties will be in 2022.
These new pea varieties provide growers with an alternative fall-sown crop to winter wheat or winter barley. This will confer benefits associated with using legumes in crop production systems such as the natural production of nitrogen fertilizer that results from the mutually beneficial interactions between pea roots and soil bacteria, especially Rhizobium leguminosarum. Commercial sources of Rhizobium leguminosarum inoculant were obtained from several sources. Endemic bacterial strains will be collected in Fall 2021 from plants grown from uninoculated seed sown in fields with no recent history of the use of commercial inoculants. This project has had two vacancies, a Research Agronomist (Soil Microbiologist) and a Research Technician, which delayed efforts to determine genotypes (DNA fingerprints) of rhizobia isolates. However, excellent candidates were identified for each position and it is anticipated that the two selected candidates will begin later this year.
In support of Sub-objective 1B, the yield and hundred seed weights of 750 pea genetic resources harvested in 2020 were determined that demonstrated both cold and drought tolerance for planting in the fall of 2021. In addition, these lines were able to be scored for resistance to pea weevil that naturally impacted the field trial and lines with resistance were identified.
In support of Sub-objective 2A, a population of 170 pinto bean lines were evaluated for reaction to white mold under high nitrogen and excess irrigation treatments in a replicated field trial. Genetic analysis revealed a few genes that exerted major effects on tolerance to lodging, which is when a plant cannot support its own weight and falls over, days to mature, and resistance to white mold disease. A seed increase of the 170 lines is ongoing so a second field trial can be conducted in 2022 to confirm these findings. A different population of 156 bean lines was evaluated for white mold resistance in a greenhouse. A major resistance gene that has been named “WM5.4” was identified. The same 156 lines were also planted in the white mold disease field nursery in 2021 and we are awaiting results for confirming the importance of the WM5.4 gene in disease resistance. Forty different populations were also made from crosses between 19 pinto bean lines that are resistant to white mold disease.
In support of Sub-objective 2B, the DNA sequences of the internal transcribed spacer region (ITS) were determined for 234 fungal isolates collected from winter pea roots in 2019. These will be examined to identify the fungal plant pathogens that reduce winter pea yields in field that received different amounts of precipitation. In addition, six fungicidal seed treatments were evaluated in a field trial to identify treatments that can control Fusarium root rot of peas. In addition, pea accessions (444 lines) from the Pea Core Collection and 28 commercial pea varieties were screened for a second time for resistance to Fusarium avenaceum. These results are being used to identify both new sources of disease resistance and genes responsible for disease resistance.
Accomplishments
1. Fusarium root rot pathogens of fall-sown peas identified. Fusarium root rot is a serious disease of spring peas that can reduce yields by 60% when disease pressure is severe. Fall-sown, or “winter”, peas are a completely new crop in Washington and there is little known about the fungal pathogens that cause Fusarium root rot in fall-sown peas. ARS researchers in Prosser, Washington, used DNA sequencing to identify the pathogens that were primarily responsible for Fusarium root rot in fall-sown peas. The most prevalent pathogens were Fusarium acutatum, Fusarium rubicola, and Fusarium citricola. Isolates of these pathogens can be used to screen pea lines to identify those that combine disease resistance with food grade quality and winter hardiness for developing improved fall-sown peas.
