Species Diversity and Toxigenic Potential of Fusarium incarnatum-equiseti Species Complex Isolates from Rice and Soybean in China

Fusarium incarnatum-equiseti species complex (FIESC) strains are generally considered moderately virulent to many agricultural crops and produce a variety of mycotoxins, which represent a serious threat to food safety and public health. The occurrence of the FIESC strain in agricultural crops has been reported in various climatic regions, but detailed information on the species composition and toxigenic ability is rare in China. In this study, phylogenetic analyses were performed with combined sequences of EF-1a and RPB2 of 186 Fusarium isolates obtained from rice (Oryza sativa) and soybean (Glycine max). Twelve species were identified and 156 of the isolates were resolved within the Incarnatum clade of the FIESC species. Host influenced the population composition: rice isolates belonged to 12 species, among which FIESC 16, 18, and 24 strains were predominant; whereas five species were found among soybean isolates and FIESC 1, 16, and 18 strains dominated. Forty-three isolates were arbitrarily selected and analyzed for their Tri gene sequences and mycotoxigenic potential. Phylogenetic results based on the combined Tri5, Tri7, and Tri13 sequences were coincident with those from housekeeping markers. Type-A and -B trichothecenes were the main metabolites. Diacetoxyscirpenol was detected in all strains at varying concentrations. Nivalenol, 4-acetyl nivalenol, 3-acetyl deoxynivalenol, and neosolaniol were produced in members of the FIESC 1, 3, 7, 8, 15, 16, 17, and 18 strains. Our findings contribute valuable phylogenetic and toxigenic information necessary for the risk evaluation of mycotoxins in agricultural products.