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KEYNOTE LECTURE SESSION 3: PATHOGENESIS – EPIDEMIOLOGY AND
POPULATION GENETICS
The life cycle of a head blight pathogen, Fusarium
graminearum, and its importance to agriculture
F. Trail
Department of Plant Biology, Michigan State University, 612 Wilson Road, East Lansing, MI 48824,
USA
E-mail: trail@msu.edu
For most fungi, there are two critical stages of the life cycle: dispersal, and
survival of adverse conditions. All fungi have evolved to solve these two problems
in a niche-specific way, and arguably these are two very vulnerable stages of the
life cycle, which should be taken advantage of for disease management. F.
graminearum completes its life cycle in association with grain crops, overwintering
in the field on crop residues. The life cycle is characterized by prominent fruiting
bodies, which are major dispersal agents for disease initiation. The fruiting bodies
tie the disease from year to year, and ascospore nonproducing strains were
significantly reduced in ability to cause disease (Desjardins et al., 2006). Fruiting
bodies of F. graminearum are ephemeral, and overwintering that leads to
inoculum production has been suggested to be predominantly in the form of lipidfilled
fruiting body initials. Both chlamydospores, and hyphae within crop residues,
are also overwintering propagules, although the contribution of chlamydospores to
disease has not been shown. The genome sequence of F. graminearum is now
available and whole-genome expression has been completed for many stages of
the life cycle. Furthermore, the availability of whole genome sequences of several
other Fusarium species with different life cycle allows comparisons that can
greatly improve our understanding of the life cycles of these organisms. We and
others have used these tools to understand the life cycle, including development
and dispersal of ascospores, overwinter survival in crop residues, growth in and
on the host, and biosynthesis of mycotoxins. Studies of genomics,
transcriptomics, gene function, physiology and histology have all contributed to
the increasingly detailed picture of the fungal life cycle. We are investigating this
important pathogen as a whole organism, taking into consideration all life cycle
stages both on the host and in the soil. From these studies, we can better identify
strategies and life cycle time-points that lend themselves to control strategies.
This approach has revealed a surprisingly intimate host-pathogen relationship in
which the fungus relies on the host year-round, and has exposed adaptations of
the fungus to agricultural practices.
Keywords: perithecia, ascospores, chlamydospores
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