Résumé
Thirty isolates of Magnaporthe grisea collected from 18 provinces/cities of China representing 12 pathotypes and 9 different lineages were chosen for pathogenicity test with artificial inoculation on some rice varieties with known resistance genes, of hybrid rice, and conventional early indica and late japonica varieties cultivated in China since the 1990's. Virulence spectrum of the 30 isolates tested was very different, showing that they recognize numerous different resistance genes. Varieties also revealed very different resistance patterns showing that they carry different resistance genes or combinations of resistance genes. On the basis of comparisons with international differential varieties with known resistance genes, the presence of these resistance genes in certain Chinese varieties could be speculated. The results indicated that some varieties were resistant to most of the isolates tested and that they could be of interest as resistance sources for hybrid parents or to be planted in the field directly. (Résumé d'auteur)