Abstract: The invention concerns a novel nucleic acid fragment of the genome of rice pathogenic fungus Magnaporthe grisea comprising a gene coding for a protein (hereafter referred to as gene 763) whereof the presence and integrity are indispensable for pathogenesis of said fungus with respect to rice and barley. The invention also concerns the promoter of said gene, the gene coding for protein 763, protein 763 and uses thereof for identifying potential biological targets for novel fungicide molecules and for isolating genes coding for proteins controlling biochemical functions essential to the pathogenesis of the fungus Magnaporthe grisea with respect to rice and barley. The invention further concerns compounds inhibiting pathogenesis of fungi related to the expression of gene 763.