The competitiveness to form nodules shapes the capacities of Rhizobium leguminosarum sv viciae communities to promote symbiosis with specific hosts

National audience; Cultivated fabeae legumes (pea, fababean, lentil) develop root nodules resulting from the symbiotic interaction with Rhizobium leguminosarum sv. viciae (Rlv). Individual Rlv bacteria are able to associate with various potential hosts, but in soil they are in mixture and they display a wide range of competitiveness to form nodules (CFN). Because in Rlv, CFN and capacity to fix nitrogen are genetically independent, CFN limits the effectiveness of inoculation strategies as efficient bacteria are often outcompeted by poorly efficient Rlv bacteria of the soil community. We developed a strategy to identify bacterial genes controlling CFN. A worldwide collection of 240 Rlv isola…