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  • Author or Editor: L. Levy x
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To improve the success of vegetative propagation of Sciadopitys verticillata, stem cuttings were subjected to three treatments designed to minimize the accumulation of a latex-like sap at the cut ends of stems. A 24-hour soak in water before a hormone dip significantly enhanced rooting success and root mass. The water soak pretreatment was more beneficial to hardwood cuttings compared with softwood cuttings. Cuttings from shade-grown source trees showed the highest rooting success, but source tree age, height, and place of origin were not important factors. The water-insoluble latex-like sap had strong antibacterial activity against 3 of 11 bacterial species tested, but activity was not related to bacterial Gram reaction or the bacterial natural environment. In contrast, pine resins and latexes from selected angiosperms showed no antibacterial activity. The antibacterial component of the Sciadopitys latex-like sap was heat stable and therefore probably not protein based.

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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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