New ecofriendly antimicrobial peptides to control rice blast disease and Fusarium Head Blight.

Analogs of the peptaibol Trichogin, a natural antimicrobial peptide produced by Trichoderma longibrachiatum, have been synthesized and tested in vitro against strains of Pyicularia oryzae, causal agent of the rice blast disease, and Fusarium graminearum, responsible of the Fusarium Head Blight (FHB) disease of cereals such as wheat. The screening has demonstrated that some peptide analogs are very effective in inhibiting spore germination and fungal growth at µM concentrations. These peptides have been tested also in planta to confirm their efficacy. Treatments performed on barley, a model plant for P. oryzae infections, and rice allowed to identify peptides with different efficacy in protecting leaves from blast symptoms. Besides, treatments of wheat spikes were able to strongly reduce FHB symptoms. To investigate the mode of action of these antimicrobial peptides, microscopy analyses have been performed. Peptide treatments cause a dense agglutination of the cytoplasm, that contracts from the spore cell wall, and induce auto-fluorescence of spores, which indicates that they are non-viable. Fluorescent microscopy performed with a peptide conjugated with a fluorophore showed that peptides are located intracellularly, in the agglutinated cytoplasm. This project is part of the Scientific and Technological Cooperation Agreement between Italy and Vietnam and is funded by the Italian Ministry of Foreign Affairs and International Cooperation.