Book of Abstracts (PDF) - International Mycological Association

IMC7 Main Congress Theme II: SYSTEMATICS, PHYLOGENY AND EVOLUTION Posters
654 - A molecular taxonomic revision of the genus
Pythium
A.W.A.M. de Cock 1* , C.A. Lévesque 2 , J.E.J. Bedard 3 ,
A.M. Schurko 3 & G.R. Klassen 3
1 Centraalbureau voor Schimmelcultures, P.O.Box 85167,
NL-3508 AD Utrecht, The Netherlands. - 2 Agriculture &
Agri-Food Canada, ECORC, Summerland, B.C., V0H 1Z0,
Canada. - 3 University of Manitoba, Dept. Microbiology,
Winnipeg, Manitiba, R3T 2N2, Canada. - E-mail:
decock@cbs.knaw.nl
The genus Pythium mainly consists of plant pathogens.
Identification is based on morphology and is notoriously
difficult due to variability and overlapping of characacters.
Therefore a molecular approach was chosen to evaluate the
existing taxonomy, and to find more reliable methods for
identification and detection. All available species (approx.
100), represented by more than 500 isolates were included.
One representative isolate of each species was used for
sequencing of ITS and D1-D3 regions of the lsrDNA: all
ex-type, neo-type, authentic or otherwise well defined
representative strains. Sequences were used for both
reconstruction of phylogeny and development of speciesspecific
oligonucleotides. The latter were used in DNAarrays
for simultaneous detection of multiple pathogens in
soil samples. All strains were used in studies of RFLPs of
PCR amplified ribosomal IGS and ITS and RAPD patterns,
to reveal intraspecific variation and to establish species
boundaries. RAPD patterns were most variable; IGS
patterns proved to be useful for identification. Studies were
performed simultaneously. Phylogenetic trees showed
which species were to be compared side by side on RFLP
and RAPD gels; the latter patterns showed which
additional strains should be sequenced in case of
intraspecific variation. Results will be used to redescribe
species based on molecular groups, to provide a database
of molecular characters for identification and to develop
specific probes for detection.
655 - Elucidating the 'enigma' of Aenigmatomyces
ampullisporus which is now found as a Zygomycetous
fungus parasitizes a spermatophore of collembolan
insect
Y. Degawa
Kanagawa Prefectural Museum of Natural History, Iryuda
499, Odawara, Kanagawa 250-0031, Japan. - E-mail:
degawa@pat-net.ne.jp
Aenigmatomyces ampullisporus Castañeda and Kendrick
was described from Canada in 1993. Although the authors
assigned it to the kingdom Fungi, they could not decide to
which phylum it belonged. They gave it a name 'enigmatic
fungus' and left its appropriate taxonomic position as a
mystery to be resolved in future. From 1999 to 2002, I
collected the fungus repeatedly from Japan, which was
identified as A. ampullisporus in reference with the
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Book of Abstracts
holotype specimen. As a result of observations, the
'enigma' was resolved as follows; 1) The 'host hyphae' as
explained in the original description can no longer be a
fungal structure, but are stalks of spermatophores of
Collembola. 2) Spores infecting the head of
spermatophores swelled to become hyphal bodies. While
one of the hyphal arms elongates downward functioning as
an anchor, the other arm elongates upwards bearing
abundant sporogenous structures. In maturation,
spermatozoon in a spermatophore gradually degrades and
finally disappears entirely. 3) Spherical liquid-drops were
stained in blue at the apices of spores when mounted in
Lacto-aniline blue. 4) 'Oospores of the host' are directly
connected with the hyphal bodies. Their pigmentation and
ornamentation suggests that they are zygospores.
Consequently, A. ampullisporus is not an Oomycetesparasite
but a zygomycetous fungus parasitizing the
spermatophore of Collembola, and is probably a relative of
holocarpoic amoeba-parasites of Cochlonemataceae,
Zoopagales.
656 - Inter- and infraspecific length variability in
minisatellites in the ITS region of Leccinum (Boletales,
Boletaceae)
H.C den Bakker 1* , B. Gravendeel 1 , T.W. Kuyper 2 & M.E.
Noordeloos 1
1 Nationaal Herbarium Nederland, Leiden university
Branch, P.O.box 9514, 2300 RA, Leiden, The Netherlands.
- 2 Wageningen Agricultural University, Department of
Environmental Sciences, P.O. box 8005, 6700 EC,
Wageningen, The Netherlands. - E-mail:
bakker@nhn.leidenuniv.nl
Phylogenetic relationships of the European species of
Leccinum (Boletaceae) were investigated by maximum
parsimony, likelihood analyses and Bayesian analyses of
nrITS1-5.8S-ITS2 and 28S sequences. The separate gene
trees inferred were largely concordant, and their combined
analysis indicates that several traditional sectional and
species-level taxonomic schemes are artificial. In
Leccinum, the nrITS region ranges in size from 694 to 1480
bp. This extreme length heterogeneity is localized to a part
of the ITS1 spacer that contains a minisatellite with
tandemly repeated copies including the six-basepair
GAAAAG motif. The number of tandem repeats varied
from 2 to 6, but there were many repeat variants.
Secondary structure analysis revealed that the ITS1 spacer
in Leccinum appears to be still functional despite the
presence of the minisatellite. Intraindividual sequence
variation of the minisatellite was always smaller than
between different species, indicating that concerted
evolution proceeds rapidly enough to retain phylogenetic
signal at the infraspecific level. In contrast, the
evolutionary pattern exhibited by the major ITS1 repeat
types found was homoplastic when mapped onto the
species lineages inferred from the combined 5.8S-ITS2
sequences. The minisatellite therefore appears not to be
useful for phylogeny reconstruction at the species level.