Molecular characterization of Fusarium species associated with damping-off of conifer seedlings in tree nurseries
Fusarium can cause significant damage within conifer nurseries across the United States. Several species of Fusarium, which are morphologically similar to F. oxysporum, are known to cause damping-off, including F. commune, F. fujikuroi, F. proliferatrum, and F. solani. Isolates of Fusarium spp. (ca. 431) were collected from Idaho, Oregon, Nevada, Washington, Nebraska, Michigan, North Carolina, South Carolina, and Georgia. Initial species identification was conducted based on colony morphology. Because F. oxysporum and F. commune have almost identical colony morphology with the exception that F. commune can sporadically produce polyphialides, DNA sequencing of translation elongation factor 1-α (tef1) gene was conducted to identify Fusarium isolates. To date, tef1 sequences have been obtained for 345 of the 431 isolates of Fusarium. Using NCBI Blast, 76.7% of the isolates were identified as F. oxysporum, 8.5% as F. commune, 4.4% as F. redolens, 1.5% as F. proliferatum, 3.2% as F. fujikuroi, 1.2% as F. solani, and < 1% of F. proliferatum. Several isolates were also labeled Fusarium spp. Further work will also be discussed, such as the development of microsatellite markers for population studies of F. commune associated with different hosts and diverse geographic areas.