Population dynamics of the symbiotic mushroom Hebeloma cylindrosporum: mycelial persistence and inbreeding

Abstract

The pattern of colonization of a forest site by the ectomycorrhizal basidiomycete fungus Hebeloma cylindrosporum Romagnesi was followed from 1993 until 1997. Fruit-bodies of this tetrapolar heterothallic species were mapped, collected and propagated as pure mycelial cultures. Isolates were analysed for their mating-types and molecular markers (rDNA polymorphism and RAPD). Dedikaryotization of the 26 isolates collected in 1993 and the separate analysis of each individual haploid nucleus established that two fully compatible genets, which occupied two nonoverlapping territories, were present. Isolates belonging to the same genet could nevertheless be distinguished from each other based on Southern hybridization using hyperpolymorphic DNA probes. A majority of the 143 isolates collected from 1994 to 1997 belonged to either of the two genets identified in 1993, whose territories extended at a rate of about 0. 45-0.60 m per year. Selfing of the two 1993 genets, rather than outcrossing, was the most likely explanation for the origin of additional genotypes identified between 1995 and 1997. The spatial distribution of fruit-bodies and genets of H. cylindrosporum suggested that only a fraction of the sampled area was favourable to colonization and that genetic diversification through meiospore dispersal may be inhibited by the presence of resident genets, possibly via a somatic incompatibility system.

Recent advances in population genetics of ectomycorrhizal mushroomsRussulaspp.

“…The high replacement rate of genotypes suggested frequent sexual reproductions and short genet persistence. Similar contradictory results were observed in Hebeloma cylindrosporum (Gryta et al 1997, 2000; Guidot et al 2002). At present, the mechanisms for such conflicting results are not known.…”

Genetic diversity of ochratoxigenic <i>Aspergillus</i> section <i>Nigri</i>, using RAPD and VCG techniques

“…In addition, the values obtained for total gene diversity (HT), diversity among and within isolates (GS and GL) are similar to those observed in fungi with known sexual life cycles [23,24]. According to Grypta et al [25], regional population structure of this nature is usually the result of more frequent interbreeding events among isolates within a site than between sites and is more common in diploid or dikaryotic organisim. In summary, the high level of diversity observed in this study may be due to the ability of these isolates to undergo para sexuality under controlled field conditions [26,27] and studies have assessed neither the degree to which parasexuality occurs in natural populations nor the significance of such asexual horizontal gene transfer as an adaptive mechanism relative to migration and genetic drift [28].…”

There is high potential for the formation of common mycorrhizal networks between understorey and canopy trees in a mixed evergreen forest

“…We cannot, however, be certain that the ECM taxa that occurred on both hosts within the same core belonged to the same genotype, as the sizes of genets vary dramatically between species and locations (Dahlberg & Stenlid 1994; Gherbi et al . 1999; Gryta et al . 2000; Fiore‐Donno & Martin 2001; Guidot et al .…”