Screening of endophytes from 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 this crop 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 most conventional fungicides for seed dressing are gradually phasing out in the EU. The main disadvantage of biocontrol agents is their reduced efficacy in field conditions. Endophytes, on the other hand, show potential for plant application, as their close relationship with the host allows for higher protection against both plant diseases and abiotic stresses. The aim of the work was to isolate rice endophytes from Italian cultivars to select potential biocontrol agents for preventive seed dressing against F. fujikuroi. A total amount of 135 endophytes were isolated from rice seeds of 22 Italian rice cultivars, and from leaves and culms of 6 bakanae tolerant rice cultivars. Microbial count was performed for each plant tissue, showing an average concentration of log10 7.23 cfu/g dry weight of rice seeds and log10 5.36 cfu/g fresh weight of rice leaves and culms. In planta screenings were performed in order to select endophytes with biocontrol activity against F. fujikuroi and/or plant growth promotion of rice plants under controlled conditions. Preliminary results allowed to select 3 bacterial and 2 fungal isolates due to their ability to reduce bakanae disease severity up to 46.7%, and to enhance rice plants fresh weight up to 24.1%. The endophytic strains selected were molecularly identified and tested for abiotic stress tolerance in vitro. Further investigation on biocontrol mode of action and plant growth promotion features of the endophytic strains will also be performed to select candidates for field trials and to develop downstream stabilization and formulation.