Forum—Microbial Genomes: Unraveling Their Potential
The lead article in this issue of Agricultural
Research reports on the surprising genetic diversity of pathogens that
cause Fusarium head blight of wheat and barley, a disease that is now a
major threat to agriculture worldwide. Rather than being caused by a single
species, the disease is now known to be caused by at least eight closely
In many ways, the study of these pathogens represents a coming of age for plant
pathology, mycology, and use of microbial germplasm collections to solve
pressing problems in agriculture. The work uses state-of-the-art gene sequence
analyses to understand the genetic diversity of the pathogens. It also serves
to alert cereal breeders that multiple strains of the pathogenic lineages
should be tested to ensure durable disease resistance in new varieties of wheat
The success achieved with Fusarium is one of many examples of the
remarkable advances occurring in molecular biologyadvances that serve
agriculture as well as medicine. The genetic diversity of Fusarium could
be demonstrated only by analysis of gene sequences made possible by
technologies like chemiluminescent tagging of DNA and polymerase chain
reaction. The success was also achieved because of the availability of a
worldwide collection of Fusarium, which was needed to detect the genetic
diversity associated with pathogens that have widespread geographic
Biological resource centers, such as the ARS Culture Collection (NRRL), which
maintains 80,000 strains of agriculturally and industrially important
microorganisms, are essential for solving many problems in agriculture because
they provide access to an enormous number of genetic resources. The
availability of so many useful strains in culture collections is also a tribute
to those scientists worldwide who have made the effort to deposit strains in a
publicly accessible culture collection, with the expectation that some of these
strains would one day have further significant value.
Culture collections are a long-term investment that gives a high rate of return
because they provide germplasm for many uses. With the advent of rapid
gene-sequencing technologies, strains maintained in culture collections are
being more accurately identified and their properties predicted. So the
molecular age has increased the importance of culture collections.
Agencies such as ARS have taken the long view and supported germplasm
collections as an integral part of their commitment to agriculture. Now that
investment is paying off. Where are molecular studies taking us?
The study of Fusarium head blight is just one example of using molecular
genetic analyses to solve problems in agriculture. Gene sequencing is routinely
used to detect plant pathogens. This activity may become ever more important in
an age in which growing global travel and international trade increase
vulnerability of crops to exotic pests. These same technologies are also being
used to detect food spoilage organisms and those that cause foodborne diseases.
USDA is helping to ensure human health at home and abroad by concerning itself
with plant and animal health. The research on Fusarium fungi that reduce
crop yield and contaminate grains with toxins is helping to build a knowledge
base needed to prevent devastating crop failures and to ensure a safe and
abundant food supply.
The job is not completed. In 1994, hunger and disease associated with
malnutrition claimed the lives 10 to 12 million of the world's children under
age 5. This happened at a time when emerging plant diseases led to abandonment
of more than 2 million acres previously planted to traditional crops in Latin
Other areas ripe for progress in applied microbial research include biological
control of plant diseases, fruit rots, and insect pests. Many potential
biological control organisms are available in culture collections. But before
these organismsespecially those newly isolated from naturecan be
used they must be accurately identified by molecular techniques to help assess
Using microorganisms for bioconversion of agricultural commodities to
high-value products offers the potential for increased income to farmers. New
microorganisms are often needed in such research, and now they may be found
more readily than ever before.
An illustrative example is the recent molecular-based discovery by Stephen W.
Peterson and colleagues of 40 new species of the pharmacologically and
industrially important genus Penicillium from isolates maintained in the
ARS Culture Collection. (See "In Search of
Useful Fungi," Agricultural Research, November 1999, pp.
18-19.) This case in point further demonstrates the power of molecular
identification techniques and the importance of maintaining worldwide
collections of microbial germplasm.
Cletus P. Kurtzman
Head, Microbial Properties
"Forum" was published in the
issue of Agricultural Research magazine.