Genomic stability of two individuals of Armillaria gallica

Abstract

Large genetic individuals, or genets, of Armillaria gallica grow mitotically from a single point of origin to occupy discrete territories that often cover several hectares of forest floor. Since the expansion of these individuals must require a large number of cell divisions, somatic mutations are expected. To test this possibility, 22 isolates of A. gallica were collected from throughout the spatial territory of two individuals and 41 anonymous regions of DNA were screened for variation apparent as single strand conformational polymorphism (SSCP). Although there was abundant heterozygosity within each individual and polymorphism between the two individuals, no variation was detected among isolates within either individual. This lack of variation can be explained in two ways: (i) the mutation rate in A. gallica is substantially lower than that of other DNA based microorganisms, and/or (ii) the expansion of A. gallica individuals requires far fewer cell generations than previously estimated.

Key Words:

• mutation rate
• fungal individual
• genet
• mitotic recombination
• heterozygosity