Expression of Anti-Microbial Genes in Transgenic Grapevines for Enhanced Disease Resistance
Grapevines are susceptible to numerous diseases that devour both plants and profits. Trangenic grapevines that resist disease would provide better disease control as well as economic benefits from the reduction in spray applications. Our overall goal has been to research and develop methods to create transgenic selections of elite cultivars with improved resistance to diseases. The transgenic stragegy is especially appropriate for clonally-propagated crops, such as grapevines, where the wine industry is rooted in tradtional European Grapes with strong name recognition and very high disease susceptibility. This project has focused on cultivars Chardonnay and Merlot. Two classes of anti-microbial genes (endochitinase adn magainin-types) have been inserted into these varieties. Initial tests indicate varying degrees of improvement in resistance to powdery mildew, Botrytis bunch rot, and Crown gall disease. During two years of field testing, 3 of 4 high endochitinase expressing Chardonnay lines have exhibited resistance to Botrytis bunch rot. In addition, preliminary tests in 2003 showed reduced Botrytis infection in 3 of 5 endochitinase expressing lines of Merlot. A total of 21 lines of Chardonnay tranformed with magainin-type genes showed improved resistance to crown gall disease when inoculated with two strains of the casual bacterium. Five magainin-transgenic lines showed moderate resistance to powdery mildew disease following artificial application of a highly concentrated inoculum. A relationship was observed between magainin gene transcription and disease resistance in this group of transformed lines. Further tests are needed to ascertain the relationship between gene expression and disease resistance.