Thesis
Effects of flooding on survival of Sclerotinia and Verticillium in potato field soils of western Washington
Washington State University
Master of Science (MS), Washington State University
2011
Handle:
https://hdl.handle.net/2376/100673
Abstract
Soilborne potato pathogens respond differently to soil flooding. Studies on survival of the sclerotia and microsclerotia of two potato pathogens, Sclerotinia and Verticillium, under greenhouse and field conditions, demonstrated that flooding as a disease management strategy is promising for Sclerotinia but not for Verticillium. Under greenhouse conditions, exposing sclerotia of S. sclerotiorum to constant flooding for three weeks resulted in reduction in germination, ranging from 15 to 88%, although the sclerotia remained intact. At three months, the sclerotia disintegrated but 0 to 18% of the sclerotial fragments retained their viability. No sclerotia were recovered after six months and they completely decomposed. Germination of sclerotia was higher in water only, dried field soil and soil near field capacity treatments, and the sclerotia remained intact after six months. Flooding sclerotia for six weeks at different soil temperatures (4°, 11°, and 20 °C) showed partial disintegration of sclerotia at 11 °C and only 2% germination. At 20 °C, there was complete or near complete decomposition of sclerotia and zero germination. There was apparent reduction of germination at 4 °C although to a lesser extent and at slower rate; germination after six weeks at 4 °C was 30 to 42% while at 18 weeks, there was 0 to 6% germination. In contrast, V. dahliae appeared to be more resistant to flooding when initial inoculum density was >7 CFU/g of soil. V. dahliae was recovered from the soil even after six months flooding. This result was also reflected in field microplot experiment where V. dahliae and total population estimates of Verticillium species were higher in flooded compared to fallowed microplots after 12 months. One year after planting potatoes into microplots either previously flooded or fallowed, progress of early dying symptoms as measured by AUDPC, final percent foliar wilt, recovery of V. dahliae from sampled potato stems, and potato tuber yield were not significantly different between flooded and fallowed microplots. Flooding to eliminate S. sclerotiorum is a potential method of controlling the primary inoculum of white mold in potato fields of western Washington but not for fields with high incidence of Verticillium wilt.
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Details
- Title
- Effects of flooding on survival of Sclerotinia and Verticillium in potato field soils of western Washington
- Creators
- Jennifer Millera Niem
- Contributors
- Debbie Inglis (Degree Supervisor)
- Awarding Institution
- Washington State University
- Academic Unit
- Plant Pathology, Department of
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University; Pullman, Wash. :
- Identifiers
- 99900525012601842
- Language
- English
- Resource Type
- Thesis