Identification and pathogenicity of <i>Fusarium</i> spp. associated with the sheath rot disease of rice (<i>Oryza sativa</i>) in Indonesia

Sheath rot disease seriously limits rice productivity in several countries. In this study, Fusarium spp. were proven to be major pathogens responsible for sheath rot disease in Indonesia. The disease was initially found in 13 provinces in Indonesia. A total of 287 fungal isolates was obtained from 900 sampled leaf sheaths, and all of them were shown to be pathogenic to rice plants by artificial inoculation. Molecular identification of sheath rot pathogens was performed using the translation elongation factor 1-alpha (TEF1-alpha) gene sequencing. Morphological characterization was conducted using synthetic low-nutrient agar (SNA) using filter paper. Species within the Fusarium incarnatum-equiseti species complex (FIESC) and the Fusarium fujikuroi species complex (FFSC) were the major taxa found to be associated with the disease. The FIESC included Fusarium bubalinum, F. hainanense, F. sulawesiense and F. tanahbumbuense. The FFSC included F. andiyazi, F. fujikuroi, F. proliferatum, F. pseudocircinatum, and F. sacchari. Fusarium grosmichelii, a member of the Fusarium oxysporum species complex (FOSC), and a species within the Fusarium solani species complex (FSSC) were also found to be associated with the disease. The species in the FIESC and the FFSC are morphologically difficult to distinguish; however, some FFSC species have some diagnostic traits. This is the first study to identify the Fusarium spp. causing sheath rot disease in Indonesia through field survey, fungal isolation, pathogenicity test, molecular identification, and morphological characterization.