First report of Fusarium clavus and Fusarium ipomoeae associated with seedling diseases of cotton (Gossypium hirsutum) in New South Wales, Australia

We inform here for the first time the pathogenicity of Fusarium clavus and F. ipomoeae that belong to the F. incarnatum-equiseti species complex (FIESC) on cotton seedlings in New South Wales (NSW), Australia. FIESC isolates were often recovered from seedlings that displayed collar rot symptoms which were similar to those of Rhizoctonia rot and black root rot. Therefore, it was assumed to be a secondary pathogen. However, in the 2023-24 cropping season, we only recovered putative-FIESC isolates from two collar rot diseased samples that were collected from two geographically distant fields in NSW. Based on the DNA sequences retrieved from the translation elongation factor 1α and the RNA polymerase II second largest subunit, two representative isolates from each field were identified as Fusarium clavus and Fusarium ipomoeae . Both species were able to cause pre-emerging damping off in Petri dish assays. In pot trials, both species incited light to dark brown lesions on the collar regions that were similar to those observed in the fields. The pathogens were reisolated and reidentified; thus, fulfilling Koch’s postulate. This is the first report of F. clavus and F. ipomoeae in the FIESC causing pre-emerging damping off and collar rot of cotton in NSW, Australia.