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  • Author or Editor: M. Ravelonandro x
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Tobacco (Nicotiana tabacum cv Wisconsin 38) leaf discs were transformed with the disarmed Agrobacterium tumefaciens strain EHA101 carrying the Rol C gene from A. rhizogenes (Oono et al., Jpn. J. Genet. 62:501-505, 1987), NPT II and GUS. Shoots that regenerated on kanamycin-containing medium were confirmed transgenic through GUS assays, Southern analyses and transmission of foreign genes through the sexual cycle. Transgenic plants were as short as half the height of control plants, earlier flowering by up to 35 days, had smaller leaves, smaller seed capsules, fewer seeds, smaller flowers and reduced pollen viability. The number of seed capsules, leaf number and root density were similar between transgenic and control plants. Transgenic clones varied in the expression of the Rol C gene and transgenic plants similar or only slightly different from controls were identified. Transformation with the Rol C gene presents a potentially useful method of genetically modifying horticultural crops, particularly for flowering date, height, and leaf and flower size.

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`Wisconsin 38' tobacco (Nicotiana tabacum L.) leaf discs were transformed with the disarmed Agrobacterium tumefaciens strain EHA101 carrying the rolC gene from A. rhizogenes (Oono et al., 1987) and NPT II and GUS genes. Shoots that regenerated on kanamycin-containing medium were confirmed as transgenic through GUS assays, polymerase chain reaction (PCR), Southern blot analyses, and transmission of the foreign genes through the sexual cycle. Transgenic plants were as short as half the height of control plants; were earlier flowering by up to 35 days; and had smaller leaves, shorter internodes, smaller seed capsules, fewer seeds, smaller flowers, and reduced pollen viability. The number of seed capsules, leaf number, and specific root length were similar between transgenic and control plants. Transgenic clones varied in the expression of the rolC-induced growth alterations as did the first generation of seedlings from these clones. Such differences suggested the potential for selecting for different levels of expression. Transformation with the rolC gene presents a potentially useful method of genetically modifying horticultural crops, particularly for flowering date, height, and leaf and flower size. Chemical names used: neomycin phosphotransferase (NPTII), β-glucuronidase (GUS).

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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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