Dissertation
HARNESSING THE BENEFICIAL ATTRIBUTES OF SOIL MICROORGANISMS FOR SUSTAINABLE WEED MANAGEMENT AND SOIL FERTILITY
Doctor of Philosophy (PhD), Washington State University
01/2019
Handle:
https://hdl.handle.net/2376/118450
Abstract
Weed management and soil fertility are of paramount importance in agricultural systems. In conventional agroecosystems, they are managed almost exclusively using synthetic chemical applications, but continued reliance on these methods is neither economically nor environmentally sustainable. Utilization of soil microorganisms to promote weed control and enhance soil fertility is a promising alternative strategy. Depleting the weed seedbank in soil via microbial seed decay is an ecological approach to long-term weed management. However, prolonged dormancy and defense mechanisms enable seeds to resist pathogen attack. A soil microcosm method was developed to assess the potential of soil fungi to decay dormant weed seeds. Whole seeds and caryopses of the globally prevalent weed wild oat (Avena fatua L.) were challenged with the pathogenic fungal isolate Fusarium avenaceum F.a.1 in soil. Caryopsis decay and viability were assessed at regular intervals for up to 9 weeks. Activities of chitinase, peroxidase, and polyphenol oxidase defense enzymes were assayed in caryopses and hulls (lemma and palea). Real-time PCR primers highly specific for F. avenaceum were designed and applied to quantify F.a.1 in soil, caryopsis, and hulls. Decay was significantly greater in + F.a.1 than - F.a.1 soil and it increased over time. Caryopsis viability in + F.a.1 soil was greater than in - F.a.1 soil and it decreased over time. Defense enzymes were induced in hulls and caryopses with F.a.1 challenge, and the response varied by enzyme. These results indicate that dormant wild oat seeds are capable of mounting a complex biochemical defense response to pathogen attack and that F.a.1 is a potential organism for depleting the weed seedbank. Over 50% of ‘Concord’ grape vineyards in Washington suffer from iron (Fe) chlorosis, threatening the state’s $60 million industry. Long-term chlorosis affects vine size, uniformity, productivity, and ultimately causes vine death. Application of synthetic Fe fertilizers is not environmentally sustainable or cost-effective. Alternatively, soil microbial communities that produce Fe-solubilizing compounds may naturally increase plant-available Fe. Rooting zone soil microbial communities associated with chlorotic and healthy ‘Concord’ vines were “fingerprinted” using terminal restriction fragment length polymorphism. Bacterial and fungal isolates capable of organic acid and siderophore production were identified.
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Details
- Title
- HARNESSING THE BENEFICIAL ATTRIBUTES OF SOIL MICROORGANISMS FOR SUSTAINABLE WEED MANAGEMENT AND SOIL FERTILITY
- Creators
- Anne Terese Pollard
- Contributors
- Eugene P Fuerst (Advisor)Patricia A Okubara (Advisor)Lynne A Carpenter-Boggs (Committee Member)James Harsh (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Department of Crop and Soil Sciences
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Number of pages
- 288
- Identifiers
- 99900581420101842
- Language
- English
- Resource Type
- Dissertation