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United States Department of Agriculture

Agricultural Research Service

Related Topics

Research Project: Anaerobic Soil Disinfestion Against Soilborne Phytopathogenic Agents

Location: Crops Pathology and Genetics Research

Project Number: 5306-22000-015-39
Project Type: Reimbursable

Start Date: Jul 01, 2014
End Date: Jun 30, 2015

Objective:
1) Determine the effect of four key variables on Anaerobic Soil Disinfestation (ASD) efficiency: temperature, soil type, carbon source, and plastic mulch type on suppression of Agrobacterium tumefaciens, weeds, nematodes and key fungal pathogens under commercial nursery conditions. 2) Determine the effect of ASD treatment and post-ASD treatment application of vermicompost on pathogen control during germination of walnut hybrid rootstocks. 3) Provide nursery operators with specific ASD and/or vermicompost management programs based on their location.

Approach:
1) Field trials will be established and conducted in locations representing two different soil types and environments with differing solar radiation patterns and temperature regimes. Treatments will consist of a combinaton of 3 different carbon sources and 2 plastic mulch types and a no-treatment control. In addition, each location will have a fumigtion trial to compare the results of ASD treatments with conventional treatments. To examine the efficacy of ASD and fumigation on the target plant pathogens, nylon mesh bags containing soil amended with the pathogens will be buried in the plots prior to ASD initiation or fumigation. Pathogen abundance will be assessed at time zero, mid-way through ASD treatment, and immediately following ASD treatment. Pathogen abundance will only be assessed at time zero and following the venting period for the fumigation trials. 2) Upon completion of ASD treatments or fumigation, two furrows will be pulled within each treatment plot. Vermicompost will be added directly to one furrow per plot. For all furrows, walnut seeds will be dipped in suspensions of rifampicin-resistant A. tumefaciens and planted in the furrow. Soil surrounding seeds will be used to determine A. tumefaciens population every 2 weeks for the first two weeks and then monthly until germination. Once germinating, the walnut seeds will be harvested once a month and their roots agressively rinsed in sterile water. The rinse solution will be dilution plated on selective media to enumerate A. tumefaciens. Seedlings will be evaluated for crown gall. 3) Data from field trials will be compiled and analyzed to determine the optimum carbon source and plastic tarp for a given soil type and climate. Information from the studies will be provided to growers through annual Field days held at all field trial sites; UCCE Walnut newsletters, The UC-IPM website, and the Fruit and Nut Research Information Center website. In addition, we will present our findings at grower meetings held by farm advisors.

Last Modified: 9/23/2014
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