by Dr. David Ingram
Participate in an
Plant Pathogen Conservation
Value the Biodiversity
of the Earth
A Study of Two
Oak Species and
Potato Late Blight and
Link to the site of the
Congress of Plant
3340 Pilot Knob Road
St. Paul, MN
Biodiversity and Plant Pathogens
President of the 7th International Congress of Plant Pathology,
President of the British Society for Plant Pathology, and Regius Keeper of the Royal
Botanic Garden Edinburgh
Plant Pathologists have traditionally been concerned
with the control or elimination of plant pathogens on crops, rather than with their
conservation or with studies of their role and significance in natural ecosystems.
David S. Ingram
With the publication by the World Conservation Monitoring Centre of the
first IUCN Red List of Threatened Plants (edited by Kerry S. Walter and Harriet J.
Gillett, 1998) the plant scientific community has recently been made aware that some
34,000 species (12.5% of the world's flora) are facing extinction. Because plants are the
primary producers in most natural ecosystems, each plant species has dependent upon it
approximately 30 other species of organism. It follows that for every plant species that
becomes extinct, 30 other species go with it - many of these will be plant pathogens. But
this is only part of the problem. With the continuing rapid loss of habitats and
ecosystems world-wide, the increased use of fungicides, pesticides and herbicides in
agriculture, and the release of genetically modified organisms (GMOs), the threats to
pathogen diversity in the wild are immense.
A second, equally important threat concerns the pathogens of cultivated
plants, especially those of major crop species. Such pathogens, which are usually held ex
situ either in official culture and DNA collections or, very frequently, in personal
collections have a central role in revealing genetic diversity in potential breeding
material and provide vital screens for the development of new culivars. They are, in
addition, the raw material for much of the basic scientific research on life cycles and
genetics that generate an understanding of pathogen variation, evolution (in the short
term on crops and in the long term in natural plant populations) and population dynamics.
Finally, they constitute a potentially significant biotechnological resource of particular
importance to the genetic engineer.
This diversity is also under threat. National and international
collections are placed at risk by short term funding by governments and agencies and
reliance on commercial sources of income. A steady decline in the numbers of pathogen
systematists, brought about by ignorance of the importance of systematics and changes in
scientific fashion, will undermine the curation of those collections that survive. And
finally, a lack of awareness on the part of funders and institution managers of the
importance of unique collections built up over a long career by individual plant
pathologists and breeders, will lead to significant losses of these irreplaceable
resources, especially at a time when institutions must work to short planning horizons, or
have limited life.
It is my view that there is an urgent need for plant pathologists to
address the following issues.
1. Do we know enough about the diversity and significance of plant
pathogen populations in natural ecosystems?
I suggest that we do not. The decline of the "naturalist
tradition" in Europe, the increasing concern of governments to fund research that has
economic significance rather than being curiosity led and a preoccupation with cells and
molecules rather than whole organisms and populations has resulted in a decline rather
than an increase in our knowledge of plant diseases among wild populations of plants. In
the tropics and subtropics efforts have largely focused on studies of the diversity and
ecology of higher plants and animals, with scant attention being paid to pathogens except
where they pose a threat to adjacent crop plants. We remain woefully ignorant of the huge
diversity of pathogens that affect the algae, the wild plants of the oceans and lakes,
despite the fact that c. 50% of all photosynthetic productivity on earth takes place in
It is high time that a significant international effort was made
Catalogue the diversity of plant pathogens in natural ecosystems,
with particular emphasis being placed upon species-rich ecosystems such as rainforests,
grasslands and the oceans. Why is there no "Red Data Book" for pathogens? Do we
have enough pathogen systematists?
Build on the already excellent work on the population genetics of
key pathogens in natural ecosystems, including the oceans and lakes, to greatly extend our
knowledge in this sphere. Intensify research on the ecology and physiology of the
interaction between pathogens and their hosts in wild ecosystems, focusing especially on
reproduction and population dynamics.
Initiate studies on the effects, real or potential, of the
release of fungicides, pesticides and GMOs into the environment.
Consider how studies of pathogens in natural ecosystems may
contribute to a better understanding of how plant disease may be controlled in sustainable
agricultural systems or may be used in the development of entirely new control strategies
for diseases, pests and weeds.
Consider whether pathogens of wild species should be conserved in
situ or ex situ in collections.
2. Are adequate systems in place to ensure the survival, growth and
adequate curation of ex situ collections of crop pathogens or their DNA? And is sufficient
research effort being directed towards crop pathogen systematics, evolution, genetics and
I suggest that the answers to both questions is "no". The
economic, social and political climate in which most of us operate is such that
short-termism, cost-cutting and scientific fashion all militate against a "yes"
answer to either question.
It is time for a concerted effort to: Assess the true "value",
not "cost" of collections of pathogens of crops. Assess the threats to the
survival of collections, large and small and work for their preservation, curation and
development . Identify the lacunae in our knowledge of crop pathogen biology and genetics,
particularly details of life cycles, and give appropriate acknowledgement and funding to
research that addresses such issues. Recognise the importance of fungal and microbial
systematics and seek funds to support this aspect of research and the training of new
systematists (see also 1 above).
3. Is there a need for a policy on the conservation of plant
I suggest that among the issues that require discussion are the
following: If a conservation policy is developed, how could it operate and what should its
limits be? What can be learned from the conservation policies of other societies, such as
the British Mycological Society? Are ex situ collections enough, or should the
policy embrace in situ conservation? Would pathogens conserved in natural
ecosystems be seen as a threat to crop production? . In the conservation of natural
ecosystems, should efforts be focused on those in which important crop relatives continue
to co-evolve with important pathogens? Or should a wider view of conservation be taken?
What might be the costs and the benefits of national and international conservation
policies for plant pathogens? How many pathogen species and how much biodiversity is it
necessary to conserve? And what do we mean by "biodiversity" of pathogens?
© Copyright 1998 by The American
© Copyright 1998 by The British Society for Plant Pathology