Development of Control Methods for Eutypa Dieback Disease
OBJECTIVE 1: IMPROVED DISEASE DIAGNOSTICS AND FORECASTING.
Work has progressed on establishing sensitivity thresholds for the PCR-based diagnostic tools. Detection thresholds are being established for Eutypa DNA, mycelia and wood samples. Research has indicated that both mycelia and wood contain PCR-inhibitory substances. Current focus is on optimizing extraction procedures and sample size for effective and accurate test results. Molecular tools are currently being applied to genetically compare Eutypa isolates from different countries. Research is also underway to determine the key factors that influence spore germination. Thus far, there is good correlation of Eutypa sporulation with rain and temperature criteria.
OBJECTIVE 2: EVALUATE VITICULTURAL PRACTICES FOR IMPROVED CONTROL OF EUTYPA DISEASE.
Preliminary vineyard trial analyses indicate that higher soil fertility may lead to higher incidence of Eutypa disease. Hand cane pruning and mechanical pruning treatments are displaying lower disease incidence; as opposed to the hand spur pruning treatment which showing a higher incidence of Eutypa. The minimal pruning treatment is currently showing no signs of the disease.
OBJECTIVE 3: EVALUATION AND IMPROVEMENT OF CHEMICAL AND BIOLOGICAL CONTROL AGENTS.
Progress has been made in determining how Fusarium lateritium controls Eutypa growth. Research has confirmed that F. lateritium produces “Enniatins” which are a class of proven anti-fungal agents. Work is underway to assess the impact of these compounds on Eutypa growth and development.
OBJECTIVE 4: MECHANISMS OF HOST SUSCEPTIBILITY AND RESISTANCE.
Techniques for analysis of lignin, pectin, cellulose, and hemicellulose content were established for grape wood. Wood composition of 2 susceptible (Sauvignon Blanc and Cabernet Sauvignon) and 2 tolerant (Semillon and Merlot) were determined. Two phenolic compounds (cinnamic acid and benzoic acid) were shown to have an inhibitory effect on ascospore germination and mycelial growth of Eutypa in vitro.
OBJECTIVE 5: MECHANISMS OF FUNGAL PATHOGENICITY AND VIRULENCE.
Research has been focused on finding perithecia and on isolating axenic colonies from individual ascospores. Finding Eutypa perithecia was more difficult than anticipated. None were found in the San Joaquin Valley. Perithecia were found in a few grape vineyards in Sonoma County, and a relatively extensive collection of perithecia was made from one of these vineyards. Eutypa perithecia were not found in great quantity on native hosts (e.g. Ceanothus and Toyon) in the coastal mountains. Current efforts are on axenic isolation of ascospores, and on selection of clean, clonal progeny from the ascospores. Progress was also made in identifying new bioactive compounds from Eutypa. These potential toxins are currently being examined for possible roles in pathogenicity and virulence.
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