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COPYRIGHT 2001 Hiaring Company
Part II: Problems facing California's growers
The advent of using rootstocks... has been both a blessing and a curse. Truly the danger of vine extinction from the attacks of root phylloxera has been nullified, but the curse of introducing virus infections by either rootstock or fruiting variety has at least doubled the chances of introducing transmissible diseases in the one plant" (H.P. Olmo, 1951).
It is quite probable that many viruses commonly seen in California vineyards today came on the earliest of vinifera vines from Europe in the 1800s. But because those vines were planted on their own roots, virus disease was often latent or symptomless and passed unrecognized in California's vineyards. Only with the advent of planting on rootstock, the result of the phylloxera outbreak, and frequent grafting from one variety to another, were virus diseases spread and then recognized on a large scale. Instead of just one system, growers now had two potential sources of infection to worry about (Goheen, 1989).
Recognition Of Virus And Bacteria Diseases
Virus and virus-like diseases have probably existed in California's vineyards from the earliest years, but were poorly understood at the time and often went unrecognized or misdiagnosed. Diseases caused by virus or bacteria-related problems were often attributed instead to unsound viticultural practices. In a 1931 book proposal, Frederic T. Bioletti, first head of the University of California Department of Viticulture, addressed the issue of vine problems in a chapter entitled, "Vine Trouble Attributed to Climatic, Soil and Cultural Conditions". The chapter outline included "California vine disease" (later known as Pierce's Disease [P.D.], a bacterial infection), "red leaf" (later termed leafroll virus), and "shot berries" and "couloure" (both symptomatic of fanleaf virus, as well as other possible conditions) (Bioletti, unpublished notes).
In the mid-1930s, plant pathologists began to better understand the role of virus and virus-like diseases and their effects on plants. Pathologists began to associate vineyard problems observed over the years with this intractable group of diseases, characterizing the serious symptoms and losses that can occur with virus infection (Matthews, 1991). The progress made in identification and understanding of viruses during the '30s and '40s was applied during the ensuing years by viticulture pioneers in California's vineyards.
Work On P.D. Gives Way To Virus Investigations
Pierce's Disease of grapevines was first observed in 1884 in Anaheim and Pomona, and described by USDA plant pathologist, Newton B. Pierce. Pierce called it "California Vine Disease", and it later became known as "Anaheim disease" because of the geographic area in which it was first observed. By 1895, P.D. had destroyed 30,000 to 40,000 acres of previously thriving vineyards. It was not until the 1920s that the disease was first recorded in the San Joaquin Valley (Hewitt, 1942).
In the 1930s Harold Olmo began working on breeding P.D.-resistant grapevines. They were planted at the Agricultural Experiment Station at UCLA. Olmo found this site to be exceptionally receptive to P.D. When project funding ran out in 1938, Olmo took promising selections from the UCLA site...
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