Typescript (photocopy) / iv, 130 leaves, [6] leaves of plates : ill., maps ; 30 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, 1978?

Call number: LD2668 .T4 1933 B41 / Master of Science

Call number: LD2668 .T4 1959 E41

Call number: LD2668 .T4 1960 D73

Call number: LD2668 .T4 1963 A55 / Master of Science

Call number: LD2668 .T4 1979 M62 / Master of Science

Call number: LD2668 .T4 1966 P122 / Master of Science

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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.

Bibliography: leaves 137-163. his is a comprehensive study of induced homoeologous recombination along most of the complete genetic length of two homoeologous chromosomes in the Triticeae (7A of common wheat and 7Ai of Agropyron intermedium), using co-dominant DNA markers. Chromosome 7Ai was chosen as a model alien chromosome because is has been reported to carry agronomically important genes conferring resistance to stem rust and barley yellow dwarf virus on its short and long arms, respectively.