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Problem Addressed Washington State onion production is a $50 million crop annually, 50 percent of which is exported to the Pacific Rim. Dependency on the export market requires the production of high quality, disease-free onions and onion seed to maintain and increase international opportunities. Controversy over the significance of seedborne Botrytis as a source of inoculum for neck rot in bulb onion crops has resulted in legal suits, highlighting the need to determine the importance of seedborne inoculum causing neck rot. The lack of a certified seed assay for detection of seedborne Botrytis spp. of onion, combined with the current availability of a variety of time-consuming agar plate assays, demonstrates the need for a rapid and sensitive seed assay for neck rot fungi. Goal The goal of the project is to design an affordable, accurate test for Botrytis ssp in Washington State and to make this test available to the onion seed industry. Preliminary results indicate infected seed as the primary cause of epidemics of neck rot, making this project vitally important to the seed industry. Implications PNW states produce up to 25% of the US and world supply of onion seed. Ongoing investigations into the significance and management (using cultural practices and fungicides) of Botrytis spp. causing neck rot and scape/umbel blight in onion bulb and seed crops is helping bulb and seed growers produce healthier crops. The real-time PCR seed assay, once completed, will enable seed assays to be completed within 2 to 3 days, compared with traditional agar assays that require 2 to 3 weeks for completion. The PCR assay will allow seed companies and growers to make appropriate and timely decisions regarding the need for seed treatments (hot water, chlorine, and/or fungicide seed treatments). Furthermore, the quick turnaround of PCR seed assays will facilitate phytosanitary certification requirements of seed companies for seed lots to be shipped to various export markets. Procedures
Field trials were established in the Columbia Basin over the past three years to assess seed transmission of B. aclada. Seed lots of a commercial onion cultivar infected with B. aclada were planted each year in a randomized/replicated design near Quincy. Plants were sampled and assayed for latent infection by B. aclada. In 2004, the trial was repeated in NY and MI to examine the influence of environment on seed transmission. The PCR primers that have been developed have practical application as they enable rapid completion of seed assays within 2 to 3 days compared with traditional agar assays requiring 2 to 3 weeks for completion. Publications/Journal Articles From Project Chilvers, M.I., L.J. du Toit, and T.L. Peever. 2005. “RFLP Differentiation Of Neck Rot Botrytis spp. Present In Onion Seed Crops In Washington State, And Development Of A Real-Time PCR Assay For Detection Of These Fungi In Onion Seed. 23rd Fung. Gen. Conf., 15-20 March 2005, Pacific Grove, CA. du Toit, L.J., M.L. Derie, and G.Q. Pelter. 2004.
“Eficacy Of Fungicide Seed Treatments And Foliar Applications
For Management Of Botrytis Aclada In Onion Bulb And Seed Crops In
Washington.” Pages 93 & 185-194, In: Proc. 2004 Nat. Allium
Res. Conf., 9-10 December 2004, Grand Junction, CO. du Toit, L.J., M.L. Derie, and G.Q. Pelter, 2004. “Botrytis Species In Onion Seed Crops In Washington.” Plant Disease 88:1061-1068. du Toit, L.J., M.L. Derie, M.I. Chilvers, and G.Q. Pelter. 2004. “Evaluation Of The Significance And Management Of Seedborne Botrytis spp. Associated With Neck Rot Of Onion” Progress report. Pages 21-29, In: Proc. Pacific Northwest Vegetable Assoc. Ann. Conv. Trade Show, 17-18 November 2004, Pasco, WA. Name of Graduate Student Involved With Project Marco Costanigro Intended Graduation Date Spring 2002 |
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