Book of Abstracts (PDF) - International Mycological Association

IMC7 Monday August 12th Lectures
Phytophthoras. P. cinnamomi is the most studied of the
three, with a broad host range and global distribution. It is
introduced to Australia, where it causes ecological
destruction in some forest communities, but has negligible
impact in others. In some hosts at least, it moves in the
xylem well beyond the margin of phloem necrosis. P.
lateralis, by contrast, exhibits essentially host specific
pathogenicity in forests of the western United States.
Native Chamaecyparis lawsoniana are aggressively
attacked and killed as the pathogen colonizes the phloem in
a broad advancing front that moves up the roots into the
stem. P. quercina is associated with oak decline in Europe,
but appears to be native, or at least of long standing in
these forests. It is confined to the fine roots of susceptible
oaks, but induces symptoms far beyond the colonized
tissues. We review what is known and describe ongoing
research into the infection biology and pathogenesis of
these contrasting species, and host responses to them.
20 - Induction of defense structures in conifers: Norway
spruce as a model system and a brief phylogenetic study
V.R. Franceschi
School of Biological Sciences, Washington State
University, Pullman, WA 99164, U.S.A. - E-mail:
vfrances@mail.wsu.edu
Norway spruce was used as a model system to study
anatomical and chemical defense responses to Ceratocystis
polonica and attack by its bark-beetle vector Ips
typographus. Fungal inoculation into the phloem generated
responses within 3 wk, including increase in polyphenolic
parenchyma cell (PP cell) size and staining, wound
periderm initiation, and traumatic resin duct (TD)
formation. Fungi were not seen in samples 3 wk after
phloem inoculation, but were in some samples 6-9 wk after
inoculation. Inoculations into the cambium resulted in
partial (3 wk) or complete (6, 9 wk) fungal colonization.
This indicates that PP cells have defenses capable of
inhibiting fungal growth. Samples taken near bark-beetle
galleries had similar anatomical responses, validating the
inoculation approach. In an attempt to determine signals
involved in these reactions, we found methyl jasmonate
(MJ) induced similar anatomical and chemical responses.
A single MJ treatment induced swelling of PP cells,
increase in their phenolic contents, and formation of
additional PP cells and TDs. Treatment enhanced resin
flow and increased resistance to C. polonica. MJ
application to the oldest internode of 2-yr-old saplings also
induced TD formation, and, more surprisingly, TDs were
formed in the untreated internode. MJ was found to have
similar effects at upregulating defense responses in other
conifer trees, although surprising differences were found in
some taxa.
21 - An overview of wound response and antimicrobial
defence in eucalypts
C. Mohammed 1* , K.M. Barry 2 , A. Eyles 3 , K. Harrison 3 &
M. Hall 1
1
CSIRO Forestry and Forest Products, GPO Box 252-12,
2
Hobart, Tasmania, 7001, Australia. - School of
Agricultural Science, University of Tasmania, GPO Box
252-12, Hobart, Tasmania, 7001, Australia. - 3 CRC for
Sustainable Production Forestry, GPO Box 252-12,
Hobart, Tasmania, 7001, Australia. - E-mail:
caroline.mohammed@csiro.au
With the expanding use of regrowth eucalypt forests and
plantations for wood production, the profitability of
processing operations (particularly sawmilling) will
increasingly depend on the maximum recovery of high
quality products from relatively small logs. The quality and
value of eucalypt logs can be significantly affected by the
incidence, location and extent of discoloration and defect
resulting from kino veins, decay fungi and insect attack.
Our group is the first internationally to carry out detailed
studies of eucalypt wood defence. We seek to compare two
important Australian plantation species (E. nitens and E.
globulus) with other tree species. Our studies in the area of
eucalypt defence initially focused on the formation of a
reaction zone (antimicrobial defence barrier between
healthy and decayed sapwood). Our most recent studies
have also investigated the new tissue formed immediately
adjacent to the wound site which hitherto has been given
relatively little importance. Both reaction zone and
especially wound tissue have been found to contain a
surprising concoction of tannins, flavonoids and terpenes.
The nature and significance of these extractives and the
tissue changes observed in response to wounding and
infection in eucalypts will be examined in the broader
context of tree defence strategies.
22 - Clonality in wood-inhabiting fungi on different
spatial scales
R. Vasiliauskas * & J. Stenlid
Dept. of Forest Mycology & Pathology, Swedish University
of Agricultural Sciences, Box 7026, SE - 750 07 Uppsala,
Sweden. - E-mail: Rimvydas.Vasiliauskas@mykopat.slu.se
This presentation focuses on clonal spread in woodinhabiting
fungi and its impact on population structures
over local and large geographic areas. The work is based
on genetic and spatial data and reveals strikingly different
modes and consequences of asexual propagation in a
number of species. The following species are discussed: 1)
Heterobasidion annosum, 2) Rhizina undulata, 3) Stereum
sanguinolentum, 4) Amylostereum chailletii, 5) A.
areolatum and 6) Phlebiopsis gigantea. Clonality in those
species arises as a result of: a) mycelial growth and
colonisation of spatially separated resource units (trees)
over discrete territories (species 1 and 2); b) airborne
Book of Abstracts 9