Identification of Pathogenicity Groups and Pathogenic Molecular Characterization of f. sp. in China.

f. sp. is an extremely destructive pathogen, causing sesame Fusarium wilt disease worldwide. To clarify the pathogenicity and the genetic characters of f. sp. , we systematically investigated 69 isolates collected from major sesame-growing areas in China. Among these isolates, 54 isolates were pathogenic and 15 were nonpathogenic according to pathogenicity testing on sesame seedlings. For the pathogenic isolates, three f. sp. pathogenicity groups were defined based on the three differential sesame hosts for the first time. A translation elongation factor 1α gene tree was constructed to determine the genetic diversity of the isolates but could not separate f. sp. isolates from the nonpathogenic isolates and other formae speciales. Ten () genes (one family of effectors) were identified in f. sp. isolates by a search with the genome data, and were subsequently screened in the 69 isolates. Compared with the gene profiles in other formae speciales, the presence and sequence variations of the gene homologs directly correlated with the specific pathogenicity of f. sp. toward sesame. Furthermore, eight of these f. sp. genes were significantly expressed in sesame plants as infection of the f. sp. isolate. These findings have important significance for understanding the pathogenic basis of f. sp. isolates, and will contribute to improve the diagnostics to effectively control Fusarium wilt disease in sesame.