Soil microbiota's influence in Heterodera carotae biocontrol

Plants coexist with a diverse array of beneficial and pathogenic organisms in the surrounding soil. Through root exudates, they recruit beneficial microorganisms that provide major ecological functions. Cyst nematodes, which are major crop pests, also use these exudates as hatching signals to trigger their parasitic cycle. The “suicide hatching” biocontrol strategy utilises these root exudates as a decoy, inducing the hatching of larvae in the absence of the host. In this study, we focused on the carrot cyst nematode, Heterodera carotae, and evaluated the efficacy of this biocontrol strategy based on its positioning within the agronomic system. Indeed, an enrichment of the microbial communities is expected depending on the rotation plant and can impact the strategy. In a greenhouse, we cultivated three plants (leek, turnip and barley) commonly cultivated in rotation with carrots, in two types of soils. Cyst bags were added to these soils before applying carrot root exudates to compare the hatching efficacy depending on the previous crop background. In one soil, we observed clear patterns with a lowest hatching rate when the leek was previously cultivated. We identified a fungus (Fusarium equiseti), more abundant in the leek microbial community, which must inhibit the suicide hatching strategy.