Phylogenetic and Biological Species in the Fusarium solani Complex

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0089474Geiser Fungi in the genus Fusarium are extremely important as agents of disease in plants and animals, as producers of toxins that poison food and animal feeds, as creative producers of chemicals with potential pharmaceutical uses, and even as food for human consumption. Despite their importance, identifying fusaria is very difficult, because they offer relatively few morphological characters that are useful for discrimination. This has led to a taxonomic system where extremely diverse sets of evolutionarily distinct lineages (judged on the basis of their inability to mate and form spores) are lumped together. This project by Dr. David Geiser at Pennsylvania State University and his USDA colleague Dr. Gary Samuels focuses on the Fusarium solani species complex, a cosmopolitan group of approximately 50 diverse evolutionary lineages that has most often been considered a single species. These lineages include asexual lineages, lineages that are capable of self-fertilization, and lineages that can only cross-fertilize. Also represented are seven known mating populations, groups of isolates that can potentially interbreed, each of which may represent a distinct evolutionary lineage. This diversity includes groups of isolates that are known to cause a wide variety of diseases of plants and animals. In this project, DNA sequences from four different nuclear genes will be gathered and analyzed, to identify evolutionary lineages based on shared mutations, and the lineages so recognized will be compared with the groups defined by mating compatibility and morphological distinctness. Field work in Asia and South America with foreign colleagues will provide new collections to augment the cultures and laboratory stocks maintained at the Fusarium Stock Center by Dr. Geiser. The result of the work will be a detailed phylogenetic tree for this species complex, which can be used to find taxonomically reliable characters and to predict the likelihood of biologically interesting traits such as asexuality and pathogenicity on different hosts.