Antifungal activity of bioactive molecules isolated from agricultural waste against rice blast fungus

Developing chemicals with antifungal activity from agricultural wastes is a promising approach to reduce the environmental impact of disease management strategies in plant protection and potentially a valuable source of novel modes of action. Pyricularia oryzae is able to infect rice plants at all stages of development such as leaves, stems, nodes and panicles. The almost exclusive use of chemical fungicides, e.g. strubilurins, for rice blast managements increases the risk of emergence of fungicide resistant strains. The goal of our study was to extract bioactive compounds from grapevine wastes assessing their efficacy against P. oryzae strobilurin-resistant and -sensitive strains. We tested 28 compounds on two strobilurin-resistant and two sensitive P. oryzae strains, both on spore germination and mycelium growth inhibition. One compound inhibited the mycelial growth of resistant strains by 32% and that of sensitive strains by 58% at 0.06 mM concentration. Other two compounds completely inhibited spore germination of the resistant strains at 1mM without inhibiting mycelium growth. This preliminary work will pave the way for the synthesis of nature-derived compounds possibly acting on diverse cellular targets, exhibiting dual or multiple modes of action.