Development of Resistance to Tomato Spotted Wilt and Similar Viruses inFloral Crops Progress Report — September1994
Date August 30, 1994
Title of Project Development of Resistance to Tomato Spotted Wilt and Similar Viruses in Floral Crops
Institution where work is being conducted North Carolina State University
Amount of Endowment Grant $ 15,000
Covering Period 1/1/94 to 8/30/94
Anticipated Date of Project Completion/Final Report 12/31/95
Individual(s) Conducting Project:
(List Project Leader First)
James W. Moyer - Title Professor
Telephone Number 919/515-5802
Margaret E. Daub - Title Professor
Development of Resistance to Tomato Spotted Wilt and Similar Viruses in Floral Crops
James W. Moyer and Margaret E. Daub
North Carolina State University
- A. Project Objectives:
- To use chrysanthemum as a model system to test the efficacy of geneticallyengineering floral crops for resistance to tomato spotted wilt-like viruses.
- B. Summary of Work Conducted:
- Over the past five years we have been engaged in researchdesigned to characterize the tomato spotted wilt-like viruses which infect floral crops. This
research led to the discovery that more than one virus is responsible for this disease in floral
crops and to the development of a serological assay for accurate diagnosis which is now the
industry standard. Although accurate diagnosis has helped reduce the viruses from planting
stock, they will probably never be eliminated from the production cycle and thus other measures
are necessary to provide adequate levels of control. During the last two years we have focused
our research on the development of techniques for genetic engineering of resistant plants. We
began our investigation with chrysanthemum, since this crop is economically important, is highly
susceptible to TSWV, and extensive information is available on techniques for growing these
plants in tissue culture. We are thus using chrysanthemum as the experimental model for
transformation of floral crops.
- C. Results to Date:
- Disease-resistant plants are being developed by ‘genetically-engineered crossprotection”, a process which involves transfer of a virus gene into host plants. Although the
mechanism is not understood, presence of the gene imparts virus resistance to the plant carrying
the gene. In our previous work we successfully developed, for three varieties of
chrysanthemum, protocols for regenerating plants from single cells, a necessary first step for
gene transfer. During the last year we have developed an efficient procedure for moving foreign
genes into these varieties. This procedure has proved effective for gene transfer into both pot
and cut flower mum varieties. We have recently successfully transferred a gene from TSWV
into both a cut flower and pot mum variety. Using both mechanical and thrips inoculation with
a highly virulent chrysanthemum isolate of TSWV, we have identified plants which show a high
level of virus resistance.
- D. Future Plans Covered by the Endowment Grant:
- Our goals for the coming year are focused in two major areas. First, weare working to make alterations in the virus gene. Information from other systems have
identified gene alterations which can increase the effectiveness of resistance imparted by that
gene. These altered genes are being transferred into the mum varieties and the level of
resistance tested. Second, we are testing our genetically engineered mums for resistance to
diverse isolates of TSWV. As with all disease resistance, virus isolates may exist which are able
to overcome the resistance. One of the factors which we will be investigating is how the
different altered genes affect how the plants respond to diverse isolates. Our inoculation studies
utilize both artificial mechanical inoculation and more natural inoculation using thrips. These
studies will determine the potential usefulness of the resistant varieties for commercial use.
Benefits to the Industry: The overall goal of our work is to define the potential of genetic
engineering for the development of virus resistance in floral crops. Genetic engineering is a
promising strategy for crop improvement, but has yet to be exploited by the floral crops
industry. Through our studies we are producing virus-resistant plants in one crop,
chrysanthemum, and these can be used as breeding stock for the floral industry. The
development of gene transfer protocols developed through this work can also be used for transfer
of other horticulturally relevant genes such as ones affecting flower color or senescence.
