Assessing The Impact of Floral Crop Species and Control Strategies on TSWV/INSV in Commercial Production Progress Reports - June 2002
ANNUAL PROGRESS REPORT
JUNE 2002
Project Title:
Assessing the Impact of Floral Crop
Species and Control Strategies on TSWV/INSV in Commercial Production
Researcher/Institution Information:
James
Moyer, North Carolina State University, Department of Plant Pathology, Box 7616,
Raleigh, North Carolina 27695 Phone: 919-515-7984 Fax: 919-515-7716 E-mail:
james_moyer@ncsu.edu
Industry Needs:
Tospoviruses remain a significant problem to agriculture in
the United States. Tomato spotted wilt virus (TSWV) and Impatiens necrotic spot
virus (INSV) have been recurring problems in the floriculture industry for over
15 years. They continue to impact a number of bedding plants and cut flowers
grown in greenhouses as well as field grown flowers in selected locations. The
widespread use of indexed planting material generated from propagators that
follow stringent clean stock programs has reduced the problem from acute to
chronic. TSWV and INSV can enter the production system by introducing vegetative
propagation material infected with the virus or by the introduction of
viruliferous thrips on plant material or from local sources of the thrips. Now
that improved diagnostics are available the virus can be accurately diagnosed,
however, controls for TSWV/INSV would be greatly aided if some knowledge of the
origin of the viruses could be ascertained and also how current practices
(crops, vector controls) affect the virus and thus, the probability of
subsequent virus epidemics in a greenhouse system. In addition, the efficacy of
the controls on the vectors and changes in cropping strategy can also influence
or even cause changes in the virus population similar to fungicide induced
changes in fungal pathogens. TSWV and INSV are sufficiently variable that we
believe that it is possible to determine the origin of the virus based on the
characteristic nucleotide sequence of the virus isolate as well as how various
factors influence the virus. Thus being able to determine if the virus were
introduced locally or brought into a new location from an exotic site is one
example of the practical value of this information. This knowledge would allow
growers to focus on plant sources introduced from other regions of the country
(world) or sources of infection around the greenhouses where the plants are
being produced. The overall goal of research on tospoviruses in my research
group is the study of viral genetics is influenced by changes in hosts, vectors
and control strategies. The USDA SCA funding is allowing us to examine TSWV and
INSV at the global level. This (AFE funded project) project is specifically
designed to examine how changes in the crop and other control strategies affect
the virus and thus can potentially influence future epidemics. We have already
shown that this virus can readily adapt to new genotypes in tobacco and tomato.
Thus, the goal of this research is to assess the impact of various control
strategies on virus populations so as to minimize adaptation to new or alternate
crops.
We continue to receive reports of TSWV and or INSV epidemics
in floral crop production from Europe, Japan and the US. This year (2002) we
have already also observed TSWV to reach epidemic proportions in field crops in
the Southeastern United States. This is the first TSWV epidemic in potato in
North America; incidence of the virus in excess of 30% is not uncommon. Tobacco,
pepper and tomato have also been hit hard with incidence averaging in excess of
25% and fields with 75 to 90% also observed. Infected plants frequently die and
fruit, leaves and tubers, if produced, are seldom acceptable. In 2001 peanuts
were also severely affected. With the increasing incidence in field crops, we
anticipate that local sources will become of increasing importance to the floral
crop industry.
Research Summary:
The objectives of this research are 1) to develop molecular
signatures that can be used to follow virus populations and then 2) to test how
these populations change due to crops or other control strategies. TSWV and INSV,
unlike some other viruses exist in nature as a heterogeneous mixture and thus it
will be possible to monitor changes in the population. In the first year we
recruited a graduate student, trained her in standard virological techniques and
she began characterization of representatives of distinct virus populations.
This research was complementary to the USDA grant as personnel worked together
in developing these strategies for sequencing large numbers of isolates. During
the past year they have completed working out the techniques for genomic
sequencing of TSWV and have completed the sequencing of the complete genome of
seven TSWV isolates from different locations and hosts in CA (4), CO (1), NC
(1), and Spain (1). Previous to this effort only one isolate had been completely
sequenced by anyone. We have partial sequence on several other isolates that
will be completed as part of the USDA grant. The USDA research and the research
funded by AFE will now diverge with this student working on the affects of
control strategies and crop on the populations.
This graduate student was recognized for the best research at
the departmental symposium for MS students during the last academic year. In
addition, she will be presenting this research at the annual meeting of the
American Society of Virology in July. Her committee recommended that she be
changed from the MS to the PhD program based on the outstanding progress she has
made. The specific aspects of her work that have lead to special recognition is
that while she is working on an applied problem that has high potential to
improve management strategies, she is also making significant contributions to
the level of understanding of the evolutionary biology of Tospoviruses as well
as viruses in general.
