Identification of Genotypes and the Clonal Development of Armillaria luteobubalina Watling & Kile in Eucalypt Forests

Armillaria luteobubalina is a bifactorial heterothallic fimgus with multiple alleles at the incompatibility loci. Genotypes and clones of the fungus in eucalypt forests in central Victoria were differentiated by pairings of single basidiospore isolates to determine the identity and distribution of mating alleles or by utilizing intraspecific antagonism between genetically distinct forest isolates. Both methods gave similar results although neither could distinguish between closely related genotypes. Forty-nine patches of forest vegetation infected by A. luteobubalina from c. 24 m2 to 3.5 ha in extent were mapped and isolates obtained from hosts within the patches. Of infected areas, 71% were occupied by a single genotype and the maximum number found in any one patch was three. In multiple genotype patches the different genotypes occupied separate sectors. Clones of some genotypes had a locally discontinuous distribution while others were restricted to a single location. Within areas occupied by a single genotype all hosts were infected by that genotype. Forty-four distinct genotypes were identified. Attempts to artificially inoculate stumps with basidiospores of A. luteobubalina failed. A. luteobubalina is present in these eucalypt forests as a community of genetically distinct mycelia. The size, distribution and development of clones are consistent with the hypothesis that the fungus is dispersed by both basidiospore infections and vegetative growth through host root systems.