Book of Abstracts (PDF) - International Mycological Association

IMC7 Thursday August 15th Lectures
Bodenkultur Wien, Hasenauerstrasse 38, A-1190 Vienna,
Austria. - E-mail: karin.jacobs@fabi.up.ac.za
Species of Ophiostoma are well-known as causal agents of
blue-stain in living trees and lumber, and as serious
pathogens, and occur in close association with insects,
especially bark beetles, which often function as vectors of
these fungi. In 1999, dying red spruce (Picea rubens) in a
small area of the Halifax Regional Municipality in Nova
Scotia, Atlantic Canada were infested by Tetropium
fuscum. In Europe, T. fuscum is usually a secondary pest of
Norway spruce and rarely attacks healthy trees. In this area
of Nova Scotia, T. fuscum is infesting and killing red
spruce, whose native range is restricted to northeastern
North America. Several ophiostomatoid fungi occur with
this beetle. The aims of this study were to identify the fungi
associated with T. fuscum in Halifax and compare them
with ophiostomatoid fungi associated with this insect in
Europe. Fungal associates of T. cinnamopterum
(indigenous to and transcontinental in Canada) were also
studied and compared to those of T. fuscum. Species were
identified based on morphological and molecular
characters. Ophiostoma tetropii is the most common
species associated with T. fuscum in Europe and Canada,
probably introduced into Atlantic Canada by this insect. O.
tetropii was only isolated from trees initially attacked by T.
fuscum. Other species isolated from trees attacked by both
T. fuscum and T. cinnamopterum include O. piceae, a
secondary colonizer of conifer sapwood, and the rarely
reported Pesotum fragrans.
299 - Surviving life in the fast lane: sex and clonality in
Ophiostoma novo-ulmi
C.M. Brasier * & J.F. Webber
Forest Research Agency, Farnham, Surrey GU10 4LH,
U.K. - E-mail: clive.brasier@forestry.gsi.gov.uk
On several continents the Dutch elm disease pathogen
Ophiostoma novo-ulmi is the fungal equivalent of an
adventurous tramp. Having left its original home or centre
of origin and 'jumped aboard a moving express train' (a
spreading series of Dutch elm disease epidemics) it has had
to cope with a many new and challenging events, processes
and opportunities. 'Positive' opportunities include less
distraction from competition between genotypes (a
consequence of founder effects and selection), escape from
natural enemies, an abundance of beetle vectors combined
with a highly susceptible host, easier access to the
saprotrophic phase and easier access to the vectors.
'Negative' changes include increased risks from threats
such as virus infections and sibling species and, potentially,
a reduced opportunity for genetic variation if the
environment changes. The impact these lifestyle changes
appear to have had on the pathogens fitness, behaviour and
population structure will be discussed, with special
reference to sexual and asexual reproduction, clonality, the
influence of fungal viruses and the role of outcrossing and
horizontal gene transfer.
300 - Hosts, insects, sex, aleurioconidia and the
evolution of Ceratocystis
T.C. Harrington * , A.E. Paulin-Mahady & J. Steimel
Iowa State University, Department of Plant Pathology,
Ames, Iowa 50011, U.S.A. - E-mail: tcharrin@iastate.edu
Phylogenetic analyses of rDNA sequences and a portion of
the MAT-2 gene show Ceratocystis to be monophyletic and
most closely related to Gondwanamyces and more distant
to the Microascales. Five major clades are found within
Ceratocystis. The C. fimbriata complex and C. albofundus
form a basal clade. Species in the C. paradoxa clade are
pathogens on monocots. The Thielaviopsis basicola clade
includes four soilborne, asexual species. The C.
coerulescens clade lacks aleurioconidia and includes a
subclade adapted to the Pinaceae. The remainder of the
species group loosely in the C. moniliformis clade, which
includes C. adiposa, C. fagacearum, and three asexual
symbionts of ambrosia beetles: Ambrosiella xylebori, A.
hartigii, and A. ferruginea. Characters found in the basal C.
fimbriata clade and in one or more of the other clades were
likely present in the most recent ancestor of Ceratocystis.
The hypothesized ancestor was a wound-colonizer of
woody dicots, insect-dispersed, and homothallic
(unidirectional mating type switching); had hat-shaped
ascospores accumulating at the tip of long-necked
perithecia; and formed both endoconidia (Chalara-like)
and aleurioconidia (pigmented, thick-walled spores that can
survive in insect frass and soil). Shifts to heterothallism,
loss of sexual reproduction, loss of aleurioconidia,
adaptations to monocots or the Pinaceae, and bark beetle or
ambrosia beetle symbiosis appear to have occurred in one
or more lineages of Ceratocystis.
301 - Relationships amongst Ceratocystis polonica,
Ceratocystis laricicola and their bark beetle vectors in
Europe and Asia
M.J. Wingfield 1* , M. Marin 1 , T. Kirisits 2 , O. Preisig 1 &
B.D. Wingfield 1
1 Forestry and Agricultural Biotechnology Institute (FABI),
University of Pretoria, Pretoria, South Africa. - 2 Institute
of Forest Entomology, Forest Pathology and Forest
Protection, Universität für Bodenkultur Wien,
Hasenauerstrasse 38, 1190 Vienna, Austria. - E-mail:
mike.wingfield@fabi.up.ac.za
The pathogenic blue-stain fungus Ceratocystis polonica
occurs on various spruce species (Picea spp.) and is
associated with the bark beetles Ips typographus, Ips
amitinus and Ips duplicatus in Europe and Ips typographus
f. japonicus in Japan. Ceratocystis laricicola is the
dominant pathogenic fungus vectored by the bark beetle
Ips cembrae that infests larch (Larix spp.) in Europe and
Japan. These two fungi are morphologically identical.
However, recent studies have shown that they can be
clearly separated using a number of molecular characters
Book of Abstracts 95