Graduate Thesis Or Dissertation


Differential Effects of First Year Wheat Genotype on the Suppression of Take-All Disease and the Establishment of Suppressive Microbial Agents in the Rhizosphere Public Deposited

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  • Recent research in the UK has found that the wheat cultivar grown in the first year can have a significant impact on the amount of take-all that develops in the second year, regardless of the cultivar planted in year two. ‘Einstein’ is one such cultivar that reduces take-all disease (reduced take-all buildup or TAB) and may possess a gene that encourages favorable populations of Pseudomonas to colonize the rhizosphere. Cultivar Einstein is a parent to the wheat cultivar ‘Bobtail’ that was released by Oregon State University in 2012. This study aims to determine if the low TAB trait has been inherited by Bobtail, if the trait is robust across the UK and US field environments, and how first year Bobtail compares to other cultivars commonly grown in the PNW in regard to take-all development. The secondary objective was to determine if DAPG-producing pseudomonad prevalence is associated with reduced take-all disease, and whether these pseudomonads might play a role in establishing a priority effect by the first year cultivar. Field experiments were conducted to determine the influence of different first year wheat cultivars on take-all levels in subsequent field and greenhouse studies. PCR targeting an essential gene in the biosynthetic pathway of the antibiotic 2,4‐diacetlyphloroglucinon (DAPG) was run on serial dilutions of Pseudomonas fluorescens populations derived from rhizosphere washes of wheat planted in soil previously exposed to different wheat cultivars. We successfully identified that soil from first year Bobtail wheat consistently resulted in less take-all and accumulated significantly more 2,4-DAPG producing P. fluorescens than soil from other cultivars (p<0.001), and that the two effects were correlated (r = - 0.25, p<0.001), suggesting that Bobtail may have inherited one or more genes associated with take-all resistance and Pseudomonas accumulation from its parents. An intermediate level of take-all suppression in some other cultivars may be regulated by a different mechanism. The first-year cultivar effect dominated the response in subsequent plantings (p<0.001), and its impact was not specific to the first year cultivar. These results suggest that wheat genetics may be used to produce an environment favorable to soil microbiome components that suppress take-all, an approach that is cost effective and sustainable over conventional chemical control. This microbiome effect may be determined, in part, by populations of 2,4 DAPG-producing pseudomonads, which have also been shown to induce resistance to a diversity of other important wheat diseases.
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