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ECOLOGICAL DETERMINANTS OF POPULATION STRUCTURE AND GENE FLOW BETWEEN SYMPATRIC FUNGAL SPECIES IN THE GENUS COLLEOTRICHUM FROM DIVERSE GRASS COMMUNITIES
Impact/Purpose:
The fungal genus Colletotrichum contains several species infecting monocot hosts in both cultivated and natural grass communities. In monocultured agroecosystems, these fungi are often found as destructive pathogens, capable of inducing significant disease in the host plant. In contrast, my recent sampling of C. cereale in a natural tallgrass prairie ecosystem suggests that populations of this fungus living in diverse grass communities maintain a non-pathogenic lifestyle, with their presence never correlated with substantial disease. Preliminary multi-locus phylogenetic analysis supports the presence of a single lineage of Colletotrichum in the grassland environment, but transposon distribution data and RFLP patterns suggest that these populations may actually represent a hybrid zone between distinct Colletotrichum phylogenetic species. Part of this project is currently evaluating whether natural grasslands represent regions of hybridization for Colletotrichum species that inhabit Pooideae grasses.
- Determine species boundaries and evolutionary relationships of the Colletotrichum species inhabiting grasses of the Poaceae,
- Establish whether the populations of C. cereale from pooid grasses are dominated by a disproportionate proliferation of a few successful clonal lineages,
- Investigate the possibility that C. cereale Clade A is a recent introduction to North America and is responsible for recent epidemic levels of disease and
- Determine the extent to which ecological gradients in natural grasslands represent regions of hybridization between C. cereale Clade A and Clade B, potentially mitigating the potential of Clade A to initiate disease in these environments.
Description:
This comparative analysis will allow us to detect historical events of interest such as population fragmentations, range expansions, and colonization in the Colletotrichum species that inhabit pooid grasses. What is learned from C. cereale populations in agronomic monocultures and prairie grasslands today may help predictions, and perhaps even prevent the next cycle of disease. Such knowledge is vitally important, especially when one considers that the host range for this pathogen includes most of our major grain crops, including wheat, oats, barley, and rye. These findings will serve as a valuable technical resource, improving the ability to predict, manage, and control the movement of high-risk phytopathogens into agroecosystems. The integration of this research promises to contribute greatly to the understanding of emerging phytopathogen systems, while also serving as an important empirical study of how ecogeographic patterns relate to spatial population structure and evolutionary history.