Identification of two endophytic fungi that control Septoria tritici blotch in the field, using a structured screening approach

We applied a structured screening approach to identify biocontrol agents (BCAs) against the wheat disease Septoria tritici blotch (STB) caused by Zymoseptoria tritici, with potential for commercial use. A limitation of many screening programmes is that BCAs with an effect in vitro do not necessarily show an effect in planta. Therefore, we relied on in planta screening and aimed to optimise host and environmental compatibility of the BCAs by isolating endophytic fungi from the plant, tissue and environment of future application. Furthermore, in planta screening was complemented by a small-scale field experiment and in vitro characterisation (temperature requirements, sporulation potential and fungicide tolerance) as well as a literature search, to identify the most promising isolates. The screening approach resulted in identification of two promising fungal strains that significantly and reliably reduced STB in the highly susceptible wheat cv. Sevin by up to 75% under controlled conditions. Significant reductions of disease were also observed under field conditions in cv. Mariboss. While further validation in the field is required, the two endophyte isolates, Penicillium olsonii ML37 and Acremonium alternatum ML38, have the potential for implementation in integrated disease management strategies using both fungicides and BCAs, because of their tolerance to the fungicide prothioconazole-desthio. Integrated approaches, combining different agents, offer a more sustainable and durable way to control STB. They would allow the reduction of fungicide inputs and thus help reduce the development of fungicide resistance in the pathogen population.