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  • Author or Editor: V. Damsteegt x
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Mashua, closely related to the garden nasturtium, has been cultivated by people of the Andean highlands since Incan time; however, it is disappearing from Ecuadorean markets due to decreasing yields. The main objectives of this research were to compare 1) in vitro proliferation and rooting, and reestablishment, and 2) field plant qualities such as vigor and yield between virus-infected and virus-free plant material. Virus-free material was obtained from shoot apices about 0.2 mm in size isolated from virus-infected, in vitro maintained, microcuttings of a number of mashua lines. Mashua line had an effect on proliferation, reestablishment and tuber yield. Virus infection appeared to have a detrimental effect on the general in vitro performance of all lines. There were no differences in reestablishment between the virus-infected and virus-free plants. Although there were no overall yield differences between the virus-infected and virus-free lines, virus-infected lines produced significantly more large tubers.

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Plants transgenic for potyvirus coat protein (cp) genes have been shown to be resistant to viruses homologous and heterologous to the cp source virus. We have produced plum plants transgenic for the papaya ringspot virus (PRSV) cp gene. PRSV is a potyvirus related to plum pox virus (PPV). PRSVcp transgenic plants have been inoculated with PPV under containment conditions at the USDA Foreign Diseases-Weed Science Research Facility, Frederick, MD, and evaluated for two years. At least one plant is apparently resistant or tolerant to PPV based on symptomology, ELISA and RT-PCR assays. This suggests the potential utility of cp-mediated virus protection in tree fruits. To further test this potential, both short and long-term studies are in progress to evaluate resistance and cp expression in various organs, throughout the year and over the commercial life of individual trees. Plum plants have also been transformed with the PPVcp gene. Studies are underway to evaluate the protection derived from this cp gene.

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