Perennial soil characteristics are the main factor driving in vitro inhibition of the wheat fungal pathogen Fusarium graminearum in a French case study.

Soils are termed 'suppressive' when they can limit the emergence and propagation of plant diseases. However, little is known regarding what factors determine suppressiveness and whether they could be improved for a given soil. Agricultural practices, such as tillage systems, influence the properties of the soil, and could be a lever to improve soil suppression of pathogens. In this study, we investigated the impact of soil type and crop management practices on soil suppressiveness towards Fusarium graminearum, a major winter wheat (Triticum aestivum) pathogen. As it is transmitted via crop residues left on soil, F. graminearum is susceptible to soil suppression. Soil suppressiveness has been evaluated in more than a 100 sampled fields in the Limagne plain (Puy-de-Dôme, France), to represent a great diversity of soil types (either calcisol, vertisol or fluvisol) and cropping systems (organic, reduced tillage or intensive cropping systems). The physicochemical composition of the sampled soils and crop management practices, identified through farmer surveys, were included in a generalized linear mixed-effect model to explain soil fungistasis. A fungistasis test was performed by putting a plug of PDA-agar inoculated with Fusarium in contact with the soil and measuring the area of fungal growth. This test revealed a wide variety of soil fungistatic properties, ranging from conducive soils (22% of soil covered by fungal growth) to very suppressive soils (1% of soil covered). Suppressiveness was related to soil perennial properties (p-value <.001) rather than practices. Overall, these results show that soil type and composition play a key role in fungistasis, and that soil suppressiveness is a complex, multifactorial process. [ABSTRACT FROM AUTHOR]