Thesis (D. Sc.)--University of Adelaide, Dept. of Botany, 1996? / Includes bibliographical references.

In a series of greenhouse experiments, isolates representing serotypically distinct subpopulations of Rhizobium leguminosarum bv. trifolii recovered from root nodules of field-grown subclover Trifolium subterraneum cv. "Nangeela"), were evaluated for their symbiotic effectiveness potential, their effect on regrowth potential of subclover, and for their competitive abilities to form nodules. Isolates from the nodule dominant serotypes AS6, AS6-21, and AS21 were shown to be suboptimally effective at fixing nitrogen gas (N₂) relative to RT162X95, a highly effective commercial inoculant strain. Although the majority of isolates representing the minor nodule occupying serotypes AS27, AG4, and AP17 were also shown to be of moderate effectiveness, isolates ADS14 and RW11 of serotype AS27 were equally as effective as RT162X95. Subclover regrowth was influenced by the severity of the first harvest. Plant-isolate combinations possessing superior N₂-fixing capabilities were more adversely affected by severe clipping than were the less effective combinations. Isolate 88FL3,5, a mediocre N₂-fixing member of the nodule dominant serotype AS6, was not universally more competitive at forming nodules than other isolates. Although 88FL3,5 formed more nodules than many of the other isolates when mixed in equal numbers with each of them separately, isolates ADS14 and ADS16 significantly outcompeted 88FL3,5 even though they represented a minor nodule occupying serotype, AS27. The nodule occupying successes of 88FL3,5 or ADS16 could be overcome if their respective competitor had a numerical advantage ranging between 10:1 and 25:1. Since the soil-borne population of 88FL3,5 has been shown to outnumber other subpopulations of rhizobia in the same soil by at least 10:1, it is not surprising that it can occupy the majority of nodules on field-grown plants even in the presence of more competitive types. Why the highly effective and highly competitive members of serotype AS27 are rarely recovered from nodules of field-grown Trifolium subterraneum L. is a question that merits further study. / Graduation date: 1992

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

Thesis (Ph. D.)--University of Adelaide, 1985. / Includes bibliographical references (last 24 unnumbered leaves ).

[Truncated abstract] Evolution in two genetically diverse sown populations of subterranean clover (Trifolium subterraneum L.) was examined over 16 years at Mt Barker, a long growing season site, and at Nabawa, a short growing season site, in south-west Western Australia. One population consisted of a mixture of 40 strains sown in equal proportions, while the other was a bulk-hybrid population consisting of F2 seed from 253 crosses. Seed harvested annually and kept in cold storage was grown in an irrigated common garden at the University of Western Australia Field Station at Shenton Park, along with samples of the ancestral mixtures, to examine changes within these populations. Evolution in the strain mixture populations was measured by changes in strain frequency; strains were considered ecologically successful if their relative contribution was maintained or increased from that at sowing. Mixtures containing an additional 12 cultivars were also sown at each site to examine short-term population changes. The relative importance of 38 attributes measured in single-strain swards and spaced plants at Nabawa and Mt Barker was then related to strain success in mixtures at each site. Evolution in the bulk hybrid populations was measured in spaced plants at Shenton Park by changes in mean values and variability of 26 attributes. The ancestral populations evolved into markedly different populations at each site. Most evolution occurred within three years of sowing, due to elimination of poorly adapted genotypes. Within sites, the direction of selection was similar for both mixtures. In the strain mixture populations, different strains became dominant at each site. Divergent strains, those not identical to the sown strains, were significant components of the populations, particularly at Mt Barker, but their frequency did not increase. In the bulk hybrid populations, changes occurred in the means of 20 characters and variability declined in 11 characters at one or both sites. Appropriate flowering time was fundamental for success in both environments. At Nabawa, early flowering was crucial, while successful genotypes at Mt Barker were midseason and late flowering. Flowering time in both environments was a compromise between sufficient earliness for adequate seed production prior to the onset of summer drought, and deferment for as long as possible to allow plants to develop maximum size to compete for light in spring. The balance between these two competing forces differed in response to length of the growing season at each site

Thesis (B. Sc. Hons)--University of Adelaide, 1984. / Mounted photographs. Includes bibliographical references (leaves [62-73]).

Bibliography: leaves 144-163. / xv, 163 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / This thesis examines genetic variation in growth rate and growth form among subterranean clover cultivars in winter. The effect of plant density and sowing time on growth rate and sward structure of subterranean clover in winter and the impact of grazing intensity on morphology and nutritive value of subterranean clover is studied. It explores also genetic variation in the nutritive value of subterranean clover. / Thesis (Ph.D.)--University of Adelaide, Dept. of Agronomy and Farming Systems, 1997

Graduation date: 1993

Thesis (Ph. D.)--Dept. of Soil and Water, Waite Agricultural Research Institute, University of Adelaide, 1994. / Includes bibliographical references (leaves 146-170).

Thesis (M. Ag. Sci.)--University of Adelaide, 1956. / Typewritten copy. Includes bibliographical references.