Wednesday, August 14, 2002

Phylloxera II
I swear, this is the last Nature article.
The introduction of the glassy winged sharpshooter (Homalodisca coagulata) into California, most likely from Florida, has the potential to destroy large portions of California vineyards. This insect is an effective vector of Pierce's disease, a bacterial disease spread by xylem-feeding insects and native to the southern United States.... However, given that this insect is now established in southern California, its eventual movement throughout much of the state seems inevitable. In addition, the causal agent, the bacterium Xylella fastidiosa, is widely spread in a broad range of native and weedy plants, although limited in terms of its ability to cause disease by relatively inefficient native vectors. This combination of a new vector and common disease agent has heightened the need for new disease-resistant grape cultivars.

Resistance to a wide range of diseases is needed, but the production of wine is almost exclusively based on V. vinifera cultivars and even new hybrids within V. vinifera are poorly accepted owing to the industry's reliance on traditional and easily marketed classic wine grape cultivars. Classical breeding efforts to control Pierce's disease in table grapes are underway through introgression of resistance genes from southern US grape species into large-berried seedless V. vinifera table grapes. However, the production of wine grapes resistant to Pierce's disease will require the incorporation of resistance gene(s) via genetic engineering, owing to the reliance on classic V. vinifera wine grapes. There is an ongoing debate in the industry and by regulatory agencies as to the impact of a change in the genetic constitution of a grape cultivar and the ability to still refer to it as that cultivar. Varietal labelling is an important factor in wine marketing, and it is unclear how this will be impacted by the generation of genetically modified plants.

cf. CDFA.


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