A novel lineage in the Fusarium incarnatum-equiseti species complex is one of the causal agents of fusarium rot on melon fruits in Northeast Brazil

Fusarium rot on melon fruits is a postharvest disease and its importance in Brazil is increasing since its first report in 1999. Initially this disease was attributed to the fungus Fusarium semitectum based on pathogen morphology. However, there is controversy regarding the aetiology of this disease because, in the current species concept based on phylogenetic analysis, F. semitectum is regarded as a synonym to different Fusarium species. With the objective of elucidating the disease aetiology in Northeast Brazil, Fusarium isolates were obtained from melon fruits showing rot symptoms in the main producing areas of the country. From the phylogenetic analyses of TEF1 and RPB2 gene sequences, the isolates were identified as belonging to two phylogenetic species of the Fusarium incarnatum-equiseti species complex (FIESC), one in the Incarnatum clade (Fusarium sulawense) and the other in the Equiseti clade, which corresponds to a new lineage. The newly identified lineage is close to Fusarium lacertarum. Isolates from the two species showed morphological characteristics typical of the Incarnatum and Equiseti clades, agreeing with the molecular identification, and were pathogenic when inoculated on melon fruits. This is the first report of F. sulawense on melon fruits. The data generated in this study are potentially useful for a better management of the fusarium rot on melon.