Soil microbiota effect on the efficiency of root exudates to induce suicide hatching of cyst nematodes.

Plant-parasitic nematodes are among the most harmful pests of cultivated crops causing important economic losses. The removal of chemical nematicides requires development of alternative approaches to protect crops against nematodes. For cyst nematodes, the hatching, which is the first step of the development cycle, is stimulated by root exudates released by the host plant into the rhizosphere. Inducing “suicide hatching” of nematode larvae by root exudates could constitute an effective and innovative biocontrol method to control cyst nematodes. To anticipate the effectiveness of root exudates, many parameters, such as the microbiotic composition of soil, must be considered. To anticipate the effectiveness of this method in different environments, many parameters, such as the effect of soil microbiota on root exudates, must be taken into account. Four different agricultural soils were selected based on their physicochemical composition and their microbiota were characterized by metabarcoding. To disentangle the microbiota effect from the global soil effect on hatching, four artificial soils were obtained by inoculating a common sterile soil matrix by one of the microbiota of agricultural soils. Each soil was inoculated with cysts of Globodera pallida (which attack potato) and root exudates (two doses) were applied. After 40 days, larvae remaining in cysts were counted to determine the efficiency of root exudates to stimulate hatching. The results showed that i) in agricultural soils, significant differences of hatching were observed between soils but the hatching rate remained high with no dose effect and ii) in recolonized soils, a strong dose effect was highlighted. This study shows that abiotic and biotic factors do not jeopardize the efficiency of suicide hatching by root exudates in cyst nematodes.