Thesis (M.Ag.Sc.)--University of Adelaide, Dept. of Plant Science, 1997. / Bibliography: leaves 82-89.

Presented as Thesis (Ph. D.)--University of Wisconsin--Madison, 1924. / Cover title. Reprinted from Journal of agricultural research, vol. XXXI, no. 9 (1 Nov. 1925). Includes bibliographical references (p. 825).

Take-all of wheat, caused by Gaeumannomyces graminis var. tritici (Ggt ) is a problem wherever wheat is grown. Crop rotation is currently the only method for control. Our objectives were to develop a greenhouse bioassay and to evaluate the efficacy of mineral, chemical, and or biological agents for control, test promising agents in the field, and characterize Ggt isolates collected in Virginia. 'Jackson' soft red winter wheat seeds were planted in a Kempsville loam containing millet seed infested with Ggt or sterile millet seed in the greenhouse. Root necrosis ratings, and root and shoot weight were determined as a measure of disease severity. In the field, plots were set up with or without addition of Ggt inoculum. Effectiveness of nitrogen source, reduced manganese, and fungicide seed treatments to control take-all was determined. In greenhouse tests and in field trials plants did not yield better, significantly gain root and shoot weight due to either ammonium ions or reduced manganese, and the severity of root necrosis was not affected. Fungicide seed treatments did not significantly control take-all in the field. MON 65500, an experimental chemical, fungicides, and biological agents were tested either alone or in combination in the presence and absence of Ggt. Plants from seeds treated with MON 65500 alone or in combination with difenoconazole gained significantly greater root and shoot weight and in field trials had significantly greater grain yield over control plots. In greenhouse tests, two Bacillus spp. and a fluorescent pseudomonad were tested. Plants from bacteria-treated seeds gained root and shoot weight in only one of several tests. USDA-maintained bacterial isolates did not perform well in greenhouse bioassays or in the field, and plants from Gustafson-product-treated seed, including biological agents yielded poorly over two seasons in field trials. Little information is available on the variability of Ggt, with most information coming from Britain and Australia. Virginia and Montana Ggt, and Gga and Ggg (British isolates) were tested for virulence against 'Jackson' wheat in the greenhouse. Seeds were planted with two Ggt mycelial plugs or two sterile PDA plugs. Colony morphology, growth rates, and vegetative compatibility groups were determined. Growth rate per day and total growth was related to disease severity in greenhouse assays. For the first time, bacterial Rep primers were used to amplify Ggt DNA. Molecular techniques as well as chemical markers were used to study anastomosis between "incompatible" strains. A useful technique was developed to quickly induce perithecial formation on soybean pods which lead to ecological and agricultural concerns. / Ph. D.

Typescript (photocopy) / viii, 212 leaves, [31] leaves of plates : ill. ; 31 cm / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Plant Pathology, 1983

Typescript (photocopy) / viii, 212 leaves, [31] leaves of plates : ill. ; 31 cm / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Plant Pathology, 1983

Thesis (Ph. D.)--University of Adelaide, Dept. of Plant Science, 1995? / Includes bibliographical references.

Thesis (Ph. D.)--University of Adelaide, Dept. of Crop Protection, 1998. / Includes bibliographical references (leaves 134-151).

Thesis (Ph.D.) -- University of Adelaide, Dept. of Plant Pathology, 1983. / Typescript (photocopy).

Thesis (Ph. D.) -- Lincoln University, 2009. / Also available via the World Wide Web.

Take - all disease ( caused by Gaeumannomyces graminis var tritici, Ggt ) can be suppressed by soil microorganisms after continuous monoculture of wheat ( take - all decline, TAD ). Fluorescent pseudomonads have been implicated in this suppression. Two strategies for controlling take - ail are the in situ development of disease suppressive soil, and / or the application of a biocontrol agent. However, TAD takes up to 10 years to develop after initially high levels of disease, and the performance of bacterial biocontrol agents has been inconsistent. It is not known what environmental factors select for disease antagonists. In this work the role of diseased root lesions in directing the evolution of a native pseudomonad community, and a model disease antagonist, Pseudomonas corrugate strain 2140 ( Pc2140 ) for increased disease suppression was investigated. This work shows that root lesions are a distinct niche, supporting increased populations of total aerobic bacteria ( TAB ), pseudomonads and Pc2140 ( compared to non - lesioned sections of diseased roots and healthy roots ). Lesions selected for fluorescent pseudomonads and pseudomonads which increase take - all severity. In. contrast, lesions selected for non - pseudomonads which decrease take - all, and healthy roots selected for non - fluorescent pseudomonads which decrease take - all. It was concluded that non - fluorescent pseudomonads and non - pseudomonads were important in reducing take - all, but not fluorescent pseudomonads. Pc2140 produced multiple variant phenotypes in vitro and on wheat roots which were altered in ( 1 ) their ability to inhibit pathogens in vitro and control take - all, and ( 2 ) GC - FAME and BIOLOG profiles to the extent that some variants were identified as different species. Different sets of phenotypes were produced in vitro and on roots. After 108 weeks culture of Pc2140 on root lesions and healthy wheat roots, variant colony types were generally slightly decreased in ability to reduce take - all, and reisolates with the wild type colony morphology were generally slightly increased in ability to reduce take - all compared to the ancestral Pc2140. This is the first report on the diversification of a pseudomonad biocontrol agent on roots, and has implications for the taxonomic identification and grouping of isolates based on phenotypic characteristics. / Thesis (Ph.D.)--Department of Crop Protection, 1998.