Selection of endophytes isolated from Italian rice cultivars as biocontrol agents against Fusarium fujikuroi.

Rice is among the most important staple foods worldwide. Italy is the biggest rice producer in Europe. The main seedborne disease affecting rice in Italy is bakanae disease, caused by Fusarium fujikuroi. Typical symptoms include seedling damping off and internode elongation. Bakanae disease has become a concern for seed companies and farmers as fludioxonyl, the only conventional active ingredient allowed for F. fujikuroi control, is a candidate for substitution in the EU. The main disadvantage of biocontrol agents is their reduced efficacy in field conditions. Endophytes, on the other hand, due to their close relationship with the host, are theoretically less susceptible to abiotic stressors. The aim of the work was to select potential biocontrol agents for preventive seed dressing against F. fujikuroi among a collection of rice endophytes isolated from 24 Italian cultivars. In planta screenings were performed using a total amount of 135 isolates in order to select endophytes capable of reducing bakanae symptoms similarly to fludioxonyl under controlled conditions. The selected strains were molecularly identified and tested for their potential to inhibit F. fujikuroi in vitro. A second in vivo biocontrol efficacy assay allowed to confirm the selection of 6 endophytes, 4 bacterial and 2 fungal strains, due to their ability to reduce bakanae disease severity up to 50%. Further investigation on biocontrol mode of action and plant growth promotion features of the endophytic strains will be performed through gene expression analyses to select candidates for field trials and to develop downstream stabilization and formulation.