Mutation in long-lived individuals of the root-infecting fungus Armillaria gallica

grantor: University of TorontoLarge genetic individuals of 'Armillaria gallica' grow mitotically from a single point of origin to occupy discrete territories, often covering several hectares of forest floor. Since the expansion of territories requires a large number of cell generations over a long period of time, somatic mutations are expected to accumulate. To test this possibility, isolates were collected from spatially separated points within two large individuals of ' A. gallica', and 42 anonymous regions of genomic DNA were screened for variation apparent as single strand conformational polymorphism (SSCP). Although there was abundant variation in nucleotide sequences between the two individuals, there was no variation among isolates within either of the individuals. This result can only be explained in one of two ways. Either the mutation rate in individuals of 'A. gallica' is far lower than expected, or the expansion of individuals of this fungal pathogen involves far fewer cell generations than was previously estimated.M.Sc