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ARS Home » Pacific West Area » Pullman, Washington » Grain Legume Genetics Physiology Research » Research » Research Project #445354

Research Project: Improving Resilience of Dryland Legume Cropping Systems through Enhancement of Beneficial Microbiomes

Location: Grain Legume Genetics Physiology Research

Project Number: 2090-21600-040-000-D
Project Type: In-House Appropriated

Start Date: Oct 15, 2023
End Date: Oct 14, 2028

Grain legumes, including Autumn-sown winter pea (WP) and pinto bean, are important crops for the U.S. Pacific Northwest (PNW) and Northern Plains. Both crops can produce nitrogen fertilizer through the colonization of their roots by nitrogen-fixing soil bacteria (rhizobia). Recently, our research unit has released several new food-grade WP and spring-sown pinto bean cultivars. However, little is known about the ability of these new cultivars to establish symbiotic associations with rhizobia native to PNW soils or the extent to which these new cultivars contribute to nitrogen budgets. To improve understanding of biological nitrogen fixation (BNF) and increase the amount of nitrogen produced by BNF this project has the following objectives: Objective 1: Increase environmental resilience and profitability of WP production systems through employment of strategies that improve plant and soil microbiomes. Sub-objective 1.A: Define native components of WP root microbiomes and ability for native rhizobia to compete with commercial inoculants in dryland production systems. Sub-objective 1.B: Isolate and characterize bacteria from nodule microbiome. Sub-objective 1.C: Identify WP cultivar/rhizobia combinations and management practices, which have the most beneficial effect on soil microbiomes, health, and soil N availability. Objective 2: Enhance symbiosis, fertility management, and resilience to environmental stresses in new dry bean cultivars. Sub-objective 2.A: Evaluate the link between new pinto bean cultivars, symbiotic performance, and environmental stress tolerance.

Sub-objective 1A: Goal: Establish the best native or commercial rhizobia and microbial partners for symbiotic nitrogen fixation (SNF) in winter pea (WP) under dryland environments. The diversity and structure of WP microbiomes and plant symbiotic preferences will be evaluated for food-grade WP cultivars across Pacific Northwest (PNW) locations for several years. Plots treated with commercial inoculums will assess the ability for native rhizobia to compete with introduced rhizobia. Plant growth parameters and disease development will be corelated with nodule and root microbiome diversity and composition. Sub-objective 1B: Hypothesis: Native soils will provide WP endophytes to improve plant growth and production under dryland-stressed environments. Isolation protocols for bacterial groups will be customized. Isolated bacteria will be tested individually and as synthetic communities for abilities to form effective symbiosis with food-grade WP cultivars and abilities to protect against cold, drought, and root rot resistance. The isolated bacteria will be tested for plant growth promotion (PGP) functions. Sub-objective 1C: Hypothesis: Incorporation of WP with effective N-fixing symbiosis with rhizobia and partners in crop rotations will improve soil health, fertility and add soil N credits. Soils from fields used for identification components of WP root microbiomes (Sub-objective 1.A) will be collected. Soil microbiome and chemical composition will be evaluated to identify changes in soil N, carbon and biology caused by WP rotations. These data will be correlated with WP genotype, field management, plant growth parameters, and WP nodule microbiome composition to identify the most efficient WP genotype/rhizobia/management combinations. Sub-objective 2A: Goal: Develop and identify pinto bean cultivars with high SNF capacity under diverse production environments. A select pinto panel (SPP) of 16 cultivars will be used to examine SNF and fertility management in pinto beans. Low N field trials will focus on the effect of legume genotype (LG) on microbiome selection. Once LGs with differences in endophyte preferences are identified, their endophyte preferences will be tested under drought stress. Plant growth parameters and N fixation will be correlated with nodule microbiome profiles to identify potential PGP.