Book of Abstracts (PDF) - International Mycological Association

IMC7 Monday August 12th Lectures
16 - Systemic phenomena in pine pathosystems
P. Bonello
Ohio State University, Dept. of Plant Pathology, 2021
Coffey Road, Columbus, OH 43210, U.S.A. - E-mail:
bonello.2@osu.edu
In many herbaceous host-pathogen systems, localized
infections by pathogens or beneficial microorganisms, or
localized treatment with certain chemicals, induce wholeplant
resistance to subsequent pathogenic infections. This
phenomenon is termed Systemic Induced Resistance (SIR).
This presentation will illustrate similar phenotypes and
associated putative defense responses in three conifer
pathosystems: 1) pitch canker of Monterey pine, caused by
Fusarium circinatum; 2) Heterobasidion annosum root and
butt rot of ponderosa pine; and 3) Sphaeropsis sapinea tip
blight and canker of Austrian pine. An SIR phenotype was
recently described in Monterey pine (Bonello et al. 2001.
Systemic induced resistance in Monterey pine. Forest
Pathology 31:99-106), while systemic changes in defensive
secondary metabolism were observed in mature ponderosa
pines (in preparation). Working with potted Austrian pine
we have now observed a unique phenomenon in which
expression of SIR, or the opposite phenotype of systemic
induced susceptibility (SIS), depend on whether the
challenge infections occur on the stem or on the shoot tips.
We are now attempting to correlate this organ specific
SIR/SIS phenomenon with the expression of specific
putative defense responses of the host. The significance of
these results will be discussed along with future lines of
investigation.
17 - Longevity and plant defence: Host-pathogen
interactions in short- and long-lived tissues of trees
S. Woodward
University of Aberdeen, Department of Agriculture &
Forestry, MacRobert Building, 581 King Street, Aberdeen
AB24 5UA, Scotland, U.K. - E-mail:
s.woodward@abdn.ac.uk
Relative to many herbaceous plants, trees are subject to a
wide range of diseases during their long life cycles.
Different diseases may be classed as persistent, once
established present within the host until the tree dies, or
periodic, attacking short-lived tissues when the
environmental conditions favour pathogen development.
This presentation is focused on two broad categories of
disease which affect overall tree growth and productivity:
(1) fine root diseases and (2) secondary root diseases. The
main host species discussed will be Pinus sylvestris and
Picea sitchensis. In mature trees and under normal forest
conditions, disease of fine roots are most likely to be
periodic, killing limited sections of the fine root system,
except where prevailing microclimatic conditions favour
disease. Diseases of secondary roots, however, are often
persistent, colonising woody tissues, but remaining
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Book of Abstracts
restricted to bark or heartwood tissues unless conditions
favour pathogen development. This presentation considers
the interactions between tree roots and pathogenic fungi in
terms of host defence and the various external factors
influencing disease development.
18 - Pathogenicity of the Heterobasidion annosum
complex
Å. Olson * , M. Karlsson, M. Lind & J. Stenlid
Dept. of Forest Mycology and Pathology, Swedish
University of Agricultural Sciences, Box 7026, SE-750 07
Uppsala, Sweden. - E-mail: ake.olson@mykopat.slu.se
The outcome of an interaction between a pathogen and its
host is dependent on the genotype of the individuals
involved as well as environmental conditions. We have
taking both a genetic and a genomic approach to address
the question of what genetic factors are of importance for
pathogenicity and host specialisation in the tree pathogen
Heterobasidion annosum. In North America H. annosum is
present as two intersterile groups corresponding to
biological species with different host preferences; the Sgroup
which has spruce, fir and hemlock as its main hosts
and the P-group which has pines as its main hosts. In the
genomic approach we have sequenced 1148 randomly
picked cDNA clones from a library constructed from
mRNA of H. annosum challenged with Scots pine roots.
Contig analysis identified 339 unique contig sequences out
of which 247 were assigned a putative function deduced
from sequence similarity with proteins in public databases.
In the genetic approach we are currently preparing a
genetic linkage map using AFLP markers using a mapping
population of 97 progeny isolates from a cross between a P
and a S homokaryon. Virulence on pine has been analysed
for the 97 progeny isolates. Further studies of SP hybrids of
H. annosum have revealed an importance of the
mitochondria for virulence in pine.
19 - Phytophthora in forest trees: host-parasite
interactions
E.M. Hansen 1* , G.E.St.J. Hardy 2 & W. Osswald 3
1 Botany and Plant Pathology, Oregon State University,
Corvallis OR 97331, U.S.A. - 2 Murdoch University, Perth,
Western Australia, Australia. - 3 Technical University of
Munich, Freising, Germany. - E-mail:
hansene@bcc.orst.edu
Phytophthora is well known as a genus of agricultural
pathogens, often destructive when soil conditions favor
zoospore spread. Phytophthora species are also widespread
in many forests, but little is known about their interactions
with potential hosts. We focus this analysis on three host
tree-pathogen systems that illustrate a range of pathogenic
behaviors; by reviewing what is known, we hope to focus
attention on critical gaps in our understanding of forest