Relationship between chile peppers' heat level and plant disease resistance studied
LAS CRUCES, NM—Phytophthora blight, caused by
is a major plant disease that affects many crop species worldwide,
including chile peppers in New Mexico. Farmers' observations suggested
Phytophthora capsici caused less damage in pepper crops of the hot pepper varieties than low-heat pepper varieties.
A study published in the October 2008 issue of
by the research team of Mohammed B. Tahboub (postdoctoral researcher),
Soumaila Sanogo (plant pathologist and team leader), Paul W. Bosland
(chile pepper breeder), and Leigh Murray (statistician) set out to
determine whether or not the severity of Phytophthora blight would be
greater in low-heat than in hot chile peppers.
effective means for controlling Phytophthora blight are chile pepper
cultivars that are genetically resistant to the disease. Some resistant
lines have been identified, but currently there are no cultivars that
are resistant to the blight in all environments.
fruit become infected during prolonged periods of heavy rain and high
humidity in flooded and poorly drained fields. Prior to this study,
there had been no systematic assessment of the relationship of chile
pepper heat level to chile pepper response to
If such a connection could be found, information might have been
revealed that would assist breeding programs intended for developing
disease-resistant cultivars of pepper.
Based on documented
field observations in New Mexico, Arizona, and South Carolina, the
researchers hypothesized that peppers that produce high-heat fruits
would be more resistant to Phytophthora blight than low-heat varieties.
The study was conducted by observing infection on both the root and
fruit of different varieties of peppers included.
results of the study concluded, however, that there was no relationship
between the heat level of the pepper and the plant's resistance to
Phytophthora blight. For example, while the disease was slowest to
develop on the roots of one variety of jalapeño, it was quickest to
develop on the fruit of the same plant.
disease was faster to develop on roots and slower on fruit of all other
cultivars. As the root of the plant contains no heat-inducing agents
but the fruit does, the slow development on the root and rapid
development on the fruit of the jalapeño indicates that heat level is
not a factor.
The results of this study indicate that factors other than heat level may be involved in fruit response to
Genetic differences and cuticle thickness of the plants and fruits are
among other issues that could be relevant, but further study is
The complete study is available on the ASHS
HortScience electronic journal web site: http://hortsci.ashspublications.org/cgi/content/abstract/43/6/1846
in 1903, the American Society for Horticultural Science (ASHS) is the
largest organization dedicated to advancing all facets of horticultural
research, education and application. More information at: ashs.org