ISSN 1022-7954, Russian Journal of Genetics, 2006, Vol. 42, No. 5, pp. 539–545. © Pleiades Publishing, Inc., 2006.
Original Russian Text © A.V. Shnyreva, O.V. Shtaer, 2006, published in Genetika, 2006, Vol. 42, No. 5, pp. 667–674.
(Fr.) Kumm. belong to the class Basid-
iomycetes (order Agaricales, family Pleurotaceae).
These species are widespread in forest biocenoses of
Russian regions with moderate continental climate.
These species are popular and available as cultivated edi-
ble fungi and are second in production after champignon.
Although the fruit bodies of the two species are distinct
morphologically, fungi with partly overlapping morpho-
logical characters can be found in nature, which makes
their identiﬁcation rather difﬁcult. One of the most reli-
able tests for differentiating close species takes advan-
tage of their reproductive isolation (intersterility); i.e.,
sexual matings between two species are impossible.
Many researchers found it difﬁcult to distinguish
between closely related
by morphological characters alone, which made it pos-
sible to suggest a complex species,
lato [1–4]. In this work, we employed standard matings
and random ampliﬁed polymorphic DNA (RAPD)
markers in species differentiation.
A bifactorial sexual compatibility system, or tetrap-
olar heterothallism, is characteristic of species of the
and is controlled by two unlinked loci
with multiple alleles. Fertile progeny is generated only
when fusion involves haploids (meiotic basidiospores)
heteroallelic at both mating type loci (
When haploid strains are fully compatible, a fertile
dikaryotic mycelium (dikaryon) is formed and allows
the development of fruit bodies. If a dikaryon is not
formed after a mating of monobasidiosporous (haploid)
strains, the strains are genetically identical and have
identical alleles of the sexual compatibility loci or,
alternatively, they represent different intersterility
groups (reproductively isolated biological species).
Molecular markers are widely used in phylogenetic
analysis in order to study the relationships of fungal
species, including basidiomycetes [5, 6]. Among the
variety of molecular methods employed in mycology,
RAPD–PCR is best suitable for intraspeciﬁc differenti-
ation and demarcation of closely related species [7–11].
The objective of this work was to differentiate
between the natural isolates of oyster fungi from the
two close species by matings and RAPD–PCR analysis.
MATERIALS AND METHODS
We used dikaryotic mycelial cultures isolated from
fresh fruit bodies and monosporous isolates obtained
from spore prints of
Fruit bodies were collected at the Zvenigorod Biologi-
cal Station of Moscow State University (Odintsovskii
raion, Moscow oblast) and in Moscow parks in July and
September of 1996, 1998, and 2000 and in Voronezh in
late September 2001. The natural strains are character-
ized in Table 1. In total, 84 dikaryotic strains were iso-
lated. The strains were maintained under standard con-
ditions at the Department of Mycology and Algology,
Moscow State University.
Strains were cultured and mated on ale-wort agar
(150 ml of ale-wort, 850 ml of water, 20 g of agar) in
Petri dishes at 25
C. To isolate pure mycelial cultures,
Differentiation of Closely Related
by Mating and Molecular Markers
A. V. Shnyreva and O. V. Shtaer
Department of Mycology and Algology, Moscow State University, Moscow, 119992 Russia; e-mail: email@example.com
Received July 14, 2005
—Matings and RAPD–PCR analysis were used to differentiate two closely related basidiomycetes
, which are widespread in Russian forest biocenoses with moder-
ate continental climate. Monokaryon–monokaryon (mon–mon) and dikaryon–monokaryon (di–mon) matings
demonstrated complete reproductive isolation of the two species, which have partly overlapping morphological
traits. The prevalence of a particular species in nature was shown to depend to a great extent on the natural con-
ditions, namely, the day and night temperature ﬂuctuations. The clustering of natural
played two trends: one was associated with natural reproductive isolation of the two species (
= 0.61) and the
other, with the geographical factor (
= 0.39). A relatively recent origin is suggested for the divergence of the
two species and the reproductive barrier between them. Adaptation to natural conditions was considered to be
the main factor causing the divergence of natural
populations and, eventually, allopatric speciation.