Fusarium fujikuroi: A novel source of metabolites with herbicidal activity

This study presents the isolation and identification of a fungus (Fusarium fujikuroi) from the Brazilian Pampa biome that is able to produce phytotoxic secondary metabolites with herbicidal activity. Before selecting such promising fungus, 132 microorganisms were isolated from weed plants with infections symptoms. Each sample of isolated material was used in submerged fermentation to produce a fermented broth. Thereafter, the cells were separated by centrifugation and the supernatant was filtered. Each filtered sample (culture filtrate) was used to evaluate the herbicidal activity in the bioassays with two target plants: Cucumis sativus and Sorghum bicolor. The selection criteria consisted of analyzing germination in pre-emergence, phytotoxicity, plant height and root length in post-emergence, and lesions in detached leaf-punctured assay. The pre-emergence was the primary screening, where 11 samples of culture filtrate provided 100% inhibition of germination of both plants. These samples underwent a secondary screening, which the sample 50210 presented 25% phytotoxicity, 40% reduction of plant height, 28% reduction of root length, and necrosis and chlorosis in 70% of foliar area. The microorganism coded as SO210 was identified as a strain of Fusarium fujikuroi. Up to now, studies that attribute herbicidal activity to this fungus are scarce in the literature. Therefore, this work shows a potential activity of metabolites produced by this fungus toward the inhibition of germination and development of plant weeds.