Thesis
Relative roles of tuber- and soilborne inoculum in verticillium wilt of potato and quantification of resistance in mint
Washington State University
Master of Science (MS), Washington State University
2009
Handle:
https://hdl.handle.net/2376/103356
Abstract
Inoculum of Verticillium dahliae, causal agent of Verticillium wilt (VW) of potato, exists as soilborne microsclerotia, however, it can also be found in vascular tissue of seed tubers. The effects of intratuber inoculum on VW symptoms were measured in the greenhouse and in fields with and without prior potato rotations. Vascular infection of seed tubers did not result in significant disease symptoms, stem colonization, microsclerotia production or progeny tuber infection in the greenhouse. The incidence of V. dahliae infection in seed lots was not related to differences in yield, symptom severity or progeny tuber infection in field experiments, however, disease incidence and severity were higher in common potato rotation fields compared to long rotation fields. Results indicate that efforts to reduce primary inoculum should focus on reducing pathogen populations in the soil. Verticillium wilt is also a major constraint to mint (Mentha) production. The use of resistant cultivars is an important component of VW management and Agrobacterium-mediated transformation provides the opportunity to improve existing mint cultivars. Several M. arvensis and M. longifolia selections were evaluated for resistance to V. dahliae isolates from different hosts and vegetative compatibility groups (VCGs) in the greenhouse. Transgenic peppermint (M. x piperita) plants containing VW resistance-like sequences cloned from M. longifolia were also evaluated for resistance. V. dahliae isolates from peppermint caused significantly higher disease severity, yield reductions and plant mortality than isolates from other hosts, regardless of VCG. These data supports previous studies indicating host specificity in mint isolates of V. dahliae and suggest host origin may be a better indicator of isolate aggressiveness than VCG. Inoculations of M. arvensis and M. longifolia resulted in necrosis of the inoculated stems, however both species displayed the ability to recover from rhizomes. Both M. arvensis cultivars exhibited relatively low disease symptoms, aboveground stem colonization, yield reductions and plant mortality over repeated periods of cutback and regrowth. Transgenic peppermints containing VW resistance-like sequences did not display resistance to V. dahliae. Results indicate that the restriction of pathogen movement in aboveground stems and the ability to recover from infection may be important characteristics of VW resistance in mint.
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Details
- Title
- Relative roles of tuber- and soilborne inoculum in verticillium wilt of potato and quantification of resistance in mint
- Creators
- Jeremiah Kam Sung Dung
- Contributors
- Dennis A. Johnson (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
- 99900525078601842
- Language
- English
- Resource Type
- Thesis