Novel peptide-based control measures against the rice fungal pathogen Pyricularia oryzae

The filamentous fungus Pyricularia oryzae is the main causal agent of the rice blast disease, which accounts for 10-30% yield losses per year globally. New antimicrobial peptides, analogs of the natural peptaibol trichogin GA IV, have been synthesized and tested in vitro against several P. oryzae strains from different geographic origin. Trichogin GA IV is the main component of the mixture of peptide congeners produced by Trichoderma longibrachiatum as part of its defence mechanism against other microorganisms. Its primary sequence is as follows: Oct-Aib-Gly-Leu-Aib-Gly-Gly-Leu-Aib-Gly-Ile-Lol (where Aib is alpha-aminoisobutyric acid, Oct is the n-octanoyl group and Lol is the 1,2-aminoalcohol leucinol). All analogs were synthesized by SPPS using a cost-effective strategy. In this presentation, the synthesis and conformational analysis of the peptides are presented, together with the results obtained with our in vitro screening, that has allowed the identification of several peptide sequences very effective in inhibiting spore germination and fungal growth. Those sequences are currently being tested in vivo to confirm their efficacy in protecting rice from the blast disease. This work is part of the Scientific and Technological Cooperation Agreement between the Italian Ministry of Foreign Affairs and International Cooperation and the Department of International Cooperation of the Ministry of Science and Technology of Vietnam.