Potential for outcrossing in an apparently asexual population of Fusarium circinatum, the causal agent of pitch canker disease

Fusarium circinatum (teleomorph = Gibberella circinata) is responsible for the current epidemic affecting pine trees in native and urban forests along California's central coast. Only eight vegetative compatibility groups hav e been recovered from samples collected throughout the pathogen's range in California. This low level of diversity is suggestive of an asexually propa gating population. However, crosses conducted in the laboratory on carrot a gar;as well as on Monterey pine (Pinus radiata) twigs, reveal that Californ ia strains of the fungus are capable of undergoing sexual reproduction. Out crossing was confirmed by demonstrating vegetative incompatibility between the progeny and their parents. These results indicate that sexual reproduct ion is possible within the California population of the pitch canker pathog en.