- Fall 1999 "Update" Newsletter Article -
DNA: Studies begin in lab
Search is on at molecular level for sources of plant disease, markers, and characteristics
Copyright © 1999. All rights reserved.
The first polymerase chain reactions for grape disease detection were conducted this summer at the new Molecular Marker Laboratory at Fresno State’s Viticulture and Enology Research Center.
The reactions were created in an effort to detect incidence of Eutypa dieback in grapevine, as part of initial research conducted at the lab by biology assistant professor James Prince. Two other projects have been undertaken this year – one an effort to develop a new DNA fingerprinting technique for grapevine, the other a project to detect the presence of phytoplasms that can cause grapevine yellows disease.
The Molecular Marker Laboratory was established earlier this year to serve as a research resource for faculty and students from the Viticulture and Enology Research Center (VERC), from the broader university community, and from the supporting agricultural industry. Funding was provided by the California Agricultural Technology Institute (CATI).
The original objective of Prince’s research work was to use DNA markers to help detect the presence of grapevine yellows (GY) disease, which has caused significant yield loss in Europe, Israel, Australia, and Virginia in the United States. GY can cause veinal yellowing, margin curling, berry abortion, and shoot dieback.
Through discussions with colleagues, Prince determined that applied research at the molecular level could be conducted on behalf of large segment of the agricultural industry in the central San Joaquin Valley.
"We decided to broaden the scope of the project to include the general use of molecular markers for grapevine pathology and improvement," Prince said. Detection of disease at the molecular level involves amplification of pathogen DNA from infected tissue through a cycling process called polymerase chain reaction (PCR).
The PCR technique proved difficult in initial attempts to detect Eutypa from samples of grapevine wood, Prince reported. After several modifications of methodology, positive detection of Eutypa was seen in some samples. Once this detection process is proven effective, the disease can be detected immediately from tissue samples rather than a grower having to wait up to several years before visually detecting the problem, Prince said.
In the second project, a graduate student is attempting to establish a new DNA fingerprinting technique for grapevine using ribosomal RNA genes.
"Our hope is that we may develop cultivar-specific PCR amplification," Prince said. So far, samples have been extracted from 40 grape cultivars, including Sauvignon Blanc, Cabernet Sauvignon, Pinot Noir , Merlot, Zinfandel, Chardonney and Syrah. Analysis of the PCR products indicates that there is a sequence variability that could aid in eventual detection of specific grapevine cultivars at the molecular level.
As part of the grapevine yellows project, which is being conducted in collaboration with Dr. Tony Wolf of the Virginia Polytechnic Institute, lab researchers at Fresno State are seeking to detect the presence of disease-causing elements in leafhoppers, which have been determined to be GY carriers in Europe. Detection of the pathogen in insect vectors could become another important technique for identifying the presence of GY in a vineyard.
For more information about the lab and research opportunities, for both university and private industry, contact Prince at (559) 278-2559 or through email at jamespr@csufresno.edu.
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