Casting a Wide Net: High Throughput Screening for Competitive Rhizobia Inoculants to Enhance Nitrogen Fixation and Yield in Peas and Lentils

Growers inoculate legume seed with rhizobia to enhance symbiotic nitrogen-fixation, but outcomes are often suboptimal. Yet, there has been little modernization of rhizobia inocula. We will fill this gap by screening 96 new barcoded rhizobia strains in high-throughput competition assays on peas and lentils in live farm soils. Amplicon sequencing will quantify strains’ competitive ability and association with N-fixation and productivity across variation in hosts, microbiomes, and pests. We hypothesize: H1: Host genetics and soil microbiome will impact strain competitiveness, but some generalist strains will be more reliably competitive across conditions. H2: Some strains’ relative abundance will be more predictive of higher N-fixation and productivity, consistent with providing greater benefits, and some generalist strains will more consistently associate with higher benefit than others. Development of rhizobia inocula with outstanding and consistent competition and N-fixation abilities will enhance benefits from legume rotations for cereal crops and reduce growers’ dependence on N-fertilizer.