ENVIRONMENTAL FATE OF A GENETICALLY MARKED ENDOPHYTE IN GRAPEVINES

• Author(s): Bextine, Blake; Miller, Thomas; Hayward, C.; Lampe, David; Richards, Frank;
• Abstract: Symbiotic control employs symbiotic bacteria to deliver anti-pathogen compounds to disrupt transmission of the pathogen to new hosts. Alcaligenes xylosoxidans denitrificans (Axd), an insect and plant symbiotic bacterium, occupies same niche as the plant pathogen Xylella fastidiosa (Xf) which causes Pierces disease. We determined the fate of genetically altered Axd (RAxd) after introduction into grapevines to assess its feasibility as a symbiotic control organism to control Xf. RAxd, which expresses a fluorescent protein (DsRed), was applied to grapevines by needle inoculation, foliar spray application, or soil drench. The plants were covered with insect-resistant screening, to exclude arthropods from test plants. RAxd were detected in stems of several grapevines 2 weeks post-inoculation from each inoculation type. The amount detected at 4 weeks postinoculation declined, and RAxd was absent 6 weeks post-inoculation. RAxd was not detected in grape berries or soil samples collected around RAxd positive grapevines. This work demonstrated that transgenic Axd became established in grapevines in the field but did not thrive there. A limited lifespan of transformed Axd in grapevines would keep its population increase in check in that host plant. Re-inoculation of grapevines at 6 wk intervals would be sufficient to keep anti-pathogen products present. RAxd thrives in GWSS and citrus. Therefore, there is a good chance that GWSS would pick up the RAxd as an antimicrobial symbiont from nearby sources to render GWSS vector-incompetent.
• Publication Date: Dec 2004
• Journal: 2004 Pierce's Disease Research Symposium