Bj. Saville et al., GENETIC EXCHANGE AND RECOMBINATION IN POPULATIONS OF THE ROOT-INFECTING FUNGUS ARMILLARIA-GALLICA, Molecular ecology, 5(4), 1996, pp. 485-497
Genetic individuals, or genets, of Armillaria and other root-infecting
basidiomycetes are usually found in discrete patches that often inclu
de the root systems of several adjacent trees. Each diploid individual
is thought to arise in an unique mating event and then grow vegetativ
ely in an expanding territory over a long period of time. Our objectiv
e in this study was to describe the population from which such genetic
individuals are drawn. In a sample including 274 collections represen
ting 121 genetic individuals of A. gallica (synonym A. bulbosa) from t
wo sites in each of four regions of eastern North America, genotype fr
equencies at seven nuclear loci were not significantly different from
Hardy-Weinberg expectations. Furthermore, allele frequencies at the se
ven loci were not significantly different between regions. Additional
allelic data from four non-contiguous regions of mitochondrial DNA sho
wed little or no population subdivision over the four regions. Analysi
s of the distribution of multilocus mtDNA haplotypes revealed some clo
nal transmission of mtDNAs between genets and nonrandom mating within
sites. Despite the sharing of mtDNA types by some individuals, the ove
rall sample contained a high level of genotypic diversity. The apparen
t linkage equilibrium between some pairs of loci and the high level of
phylogenetic inconsistency among all four loci suggest the occurrence
heteroplasmy and recombination among mtDNAs of A. gallica in nature.
In laboratory matings of two haploid strains with different mtDNA type
s, a low frequency of recombination in mtDNA was detected.