Caracterização morfológica e molecular de Fusarium oxysporum latu sensu associadas a mancha-marrom da palma forrageira miúda.

Abstract

The dwarf forage palm (Nopalea cochenillifera) is one of the main sources of animal feed in the semi-arid regions of northeastern Brazil, noted for its high adaptability to waterscarce conditions. However, the occurrence of diseases has represented a significant limitation to the production of this crop, particularly brown spot, a disease that causes lesions on the cladodes and reduces the plants’ productive potential. The objective of this study was to identify and characterize the causal agent associated with brown spot of the small forage palm in production areas of the states of Alagoas and Pernambuco. Samples of cladodes with disease symptoms were collected to obtain fungal isolates. Molecular characterization was performed by sequencing the EF1-α and RPB2 gene regions, followed by phylogenetic analyses. Morphocultural evaluations and pathogenicity tests were conducted to confirm the identity and infectivity of the isolates. Molecular analyses, combined with the observed morphological characteristics, allowed the isolates to be identified as Fusarium triseptatum, a species belonging to the Fusarium oxysporum complex. Pathogenicity tests revealed symptoms characteristic of the disease, confirming the fungus’s association with brown spot of dwarf forage palm. The results obtained expand knowledge regarding the etiology of the disease and contribute to the development of future strategies for monitoring and phytosanitary management of the crop. This study constitutes the first report of Fusarium triseptatum associated with brown spot of the dwarf forage palm.