Characterization and aggressiveness of Fusarium spp. associated with root and stem rot in Carica papaya in Northeast Brazil.

In the past five years, papaya farmers in northeastern Brazil have been reporting major losses in fruit production, up to 50% in some years, due to diseases caused by soil-borne pathogens. To diagnose the causal agents of this disease's complex in the region (root and stem rots), we collected samples of root and stem from papaya plants in commercial fields exhibiting yellowing, wilting, and plant collapse. Fifteen Fusarium isolates were obtained from six production areas sampled, and Koch's postulates were carried out to confirm the pathogenicity of these isolates. Five species were identified causing this disease in the region: F. falciforme (FSSC 3+4), F. petroliphilum (FSSC 1), F. pernambucanum (FIESC 17), F. sulawesiense (FIESC 16), and F. delphinoides (FDSC). Among these species, the most aggressive was F. delphinoides, followed by F. pernambucanum, F. falciforme, and F. petroliphilum, and the least aggressive was F. sulawesiense. Our findings will aid the development of strategies to manage these disease complexes to help farmers reduce the damage caused by these pathogens in papaya in Brazil and other papaya production areas in the world.