Research in Pacific and
Caribbean Basins
on Corynespora cassiicola
The plant pathogenic fungus Corynespora
cassiicola, which causes the vegetable disease
Target Leaf Spot, has been reported on at
least 145 genera (group of similar species)
in 53 plant families and in at least 15 different
tropical or subtropical countries. Crops
that suffer the greatest yield loss due to
the fungus include cowpea, cucumber, papaya,
pepper, rubber, soybean and tomato. In Florida
alone, tomato losses caused by C. cassiicola
are over $3,000/acre, and the pathogen is
responsible for major crop losses around
the world.
Though the species has a wide range of host
plants, individual isolated strands vary
greatly in virulence and host specificity.
For the past three years, C. cassiicola has
been isolated from various hosts by researchers
at the University
of Guam (UG) as part of a CSREES Pacific
Tropical and Subtropical Agriculture Research
(T-STAR) grant: “The Impact of Invasive
Weeds on the Occurrence of the Target Leaf
Spot Pathogen.” As a result, dozens
of new hosts have been identified, including
several ornamentals and native plants.
A second related project began in October 2005,
also funded by a T-STAR grant: “Characterization
of the Species Corynespora cassiicola and
its Impact on Quarantine Regulations.” It
is a collaborative effort between the UG
and the University
of Florida.
Over the next 3 years, isolates of
C. cassiicola collected from American Samoa,
Guam, Hawaii, Palau, Saipan, and Yap in the
Pacific basin and from Florida, the Virgin
Islands, and Puerto Rico in the Caribbean
basin, will be thoroughly characterized based
on genetic data, host range, and form and
structure.
As a final project activity, researchers
are seeking C. cassiicola found on different
hosts around the world to compare with the
Pacific and Caribbean isolates. Isolates
will be examined according to sequence data,
ability to cause disease on six index hosts,
form and structure, and location. This information
will be used to clarify the occurrence of
various subspecies groupings; provide a better
understanding of the diversity within the
species; enable virulent races of C. cassiicola
to be tracked within the region; and, provide
a means to evaluate isolates for quarantine,
plant breeding, and bioherbicide considerations.
If you possess C. cassiicola isolates and
are interested in participating in the study,
contact Linley
Smith at the University of Florida or Robert
Schlub at the University of Guam.
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