Pathogenic and genetic variability of Fusarium verticillioides from maize in northern Mexico

The filamentous fungus Fusarium verticillioides is a widely distributed pathogen that causes ear, stalk and root rot of maize. This fungus also produces mycotoxins that accumulate in maize kernels. As chemical control has proven to be insufficient, new and effective disease control measures must be implemented. An improved understanding of the diversity of pathogen populations is thus crucial. Here, a set of 83 F. verticillioides isolates from a major maize-growing region of Mexico was characterized at the pathogenic and genetic diversity levels. A pathogenicity assay on maize seedlings established that all isolates were pathogenic and variable for aggressiveness, with most causing major damage on maize roots (>50% of root rotted). Genetic analysis also revealed high levels of variability, as seen by the high number of haplotypes (76), the population diversity value according to effective number of alleles (6.32), gene diversity (0.80), the polymorphic index content (0.78) and Shannon’s information index (2.06). The analysed F. verticillioides population reproduces asexually, suggesting that the observed genetic and pathogenic diversity is not the result of sexual reproduction and is probably mediated by other evolutionary forces, such as mutation, gene flow, selection and hyphal anastomosis.