Intraspecific Genetic Polymorhism of ) in the Moscow Region (Russia)

Wood-destroying fungi of the genus are among the most widespread polypore fungi in the world. The interest in their study is constantly growing due to the fact that they are producers of many biologically active substances. The most common species in central Russia is the artist’s bracket fungus, . The purpose of our study was to characterize intraspecific genetic polymorphism of sexual and somatic compatibility, as well as ITS sequence variability based on the collection of 26 natural specimens collected in various Moscow localities in 2022 and 2015. The technique developed for obtaining a sterile fertile hymenium on Petri dishes in vitro was applied for genetic analysis of mating type alleles by mon-mon and di-mon crossings. For analyzing mating compatibility alleles, the monokaryotic tester strains were obtained in mon-mon crossing for five natural isolates of the collection. Sexual compatibility of the rest natural dikaryotic isolates were tested in di-mon crossing. The mon-mon crosses demonstrated tetrapolar heterothallism in , governed by two unlinked mating type loci, and the di-mon crosses of natural isolates via monokaryotic testers revealed multiple alleles for each locus. Among the 21 natural isolates of G. applanatum, at least 8 alleles of the matA locus and 7 alleles of the matB locus were characterized. However, no intersterile groups were found within the species . Semi-compatibility in mon-mon crosses of the testers, i.e. heteroallelicity at the A-locus and similar alleles at B-locus were revealed for two dikaryotic isolates collected on the same log at a distance of two meters. Somatic compatibility was tested by pairwise splicing of dikaryotic mycelia in all possible combinations between all Moscow strains collected in 2022 and 2015. The contact zone and interaction phenotype were analyzed by estimating the degree of antagonistic reaction between the contacting mycelia: C - compatibility, W - weak antagonism; M - moderate antagonism; S - strong antagonism. Compatible somatic clones were found only within the substrate. Strong (S) antagonistic interactions with a relatively wide (2-3 mm) zone of confrontation and intense pigmentation predominated among paired isolates (with frequency of 0.46). Interestingly, six strains collected from a fallen coniferous tree of 3.5 m long were apparently vegetatively compatible clones, two of those strain having identical mating compatibility alleles. The estimated genetic variability of somatic incompatibility antagonistic responses was Hvc = 1.216 by Shannon index, that indicates on rather high level of genetic polymorphism of the determinants of somatic incompatibility as well as on multiple alleles at somatic incompatibility loci. Our results are consistent with data obtained for the Ganoderma species of southern latitudes such as the agents of palm rot and . Despite of the genetic polymorphism and multiallelicity of sexual and somatic incompatibility loci, ITS sequences among isolates demonstrated conservatism and the lack of divergence. There was no obvious differentiation on strain origin, substrate specificity, or collection time. Phylogenetic analysis also demonstrated the lack of divergence and identity of ITS sequences among strains from the Moscow region, as well as strains from St. Petersburg area. Therefore, the population in Moscow Region is concluded to be distributed over a quite large area with the little intrapopulation differentiation. However, ITS sequences are suggested to be a reliable molecular barcode for species identification/verification of natural specimens.