Pseudomonas syringae pathovar phaseolicola (Pph) is the seed borne causative agent of halo blight disease in the common bean, Phaseolus vulgaris. Gene-for-gene interactions are widespread and a very important aspect of plant disease resistance. Pph race 6 strain 1448A contains no known avirulence genes and can cause disease on all bean cultivars in the differential series; however, Pph race 4 strain 1302A contains the avirulence gene avrPphB, and causes a rapid hypersensitive response (HR) in bean cultivar Tendergreen. Screening transposon (Tn) mutant libraries may allow discovery of many known and novel genes necessary for many characteristics such as adaptations to the environment, to colonise and to cause disease. Two random Tn mutant libraries, Pph 1302A::Tn and Pph 1448A::Tn were created using Tn IS-Ω-Km/hah. Pph mutants were successfully produced using the optimized conditions. A total of 960 mutants in Pph strains 1302A and 1448A were tested for their phenotypic characterisation and for identification of genome mobility in Pph 1302A and competence genes in Pph 1448A. To investigate genes involved in Pph colonisation of plants and evolution of Pph pathogenesis by HGT, the Tn mutant libraries were screened for changes in bacterial phenotypic characteristics such as colony morphology, motility, biofilm formation, growth rate in bean apoplastic fluid and conjugation. Selected mutants were assessed for in vitro and in planta growth rate and pathogenicity. Results showed that number of Pph mutants with different phenotypes caused restriction of growth in plants and/or reduced symptoms. In colony morphology screening, 28 small (11 Pph 1302A and 17 Pph 1448A) and 29 big (four Pph 1302A and 25 Pph 1448A) colony variant mutants were obtained. Eight Pph mutants showed highly reduced colony size and were also affected in both swarming and swimming motility. One very small colony mutant had a Tn insertion in the gene for HdtS protein which is involved in quorum sensing of bacteria. Among 29 big colony mutants, a Tn insertion in the gene for outer membrane protein A (OmpA) affected colony morphology, motility and highly impaired in planta growth and pathogenicity symptoms. Other phenotypic screening methods included motility tests, where several Pph mutants showed highly reduced swarming and swimming motility. Six Pph 1302A::Tn mutants showed some reduction in biofilm formation/attachment. Three Pph 1302A::Tn mutants had a higher growth rate in minimal media supplemented with apoplastic fluid. Two Pph 1448A::Tn mutants showed significantly reduced growth rate in vitro in Luria Bertani liquid media. Finally, eight Pph 1448A::Tn mutants showed complete absence of disease in bean pods. These results demonstrate the identification of many genes involved in key bacterial behaviour and are important for plant colonisation and therefore disease in bean plants. Screening for genome mobility by Pph 1302A::Tn mutant library showed three Pph 1302A::Tn mutants which may have the ability to transfer from Pph 1302A to Pph 1448A. These mutations were in areas of the genome associated with antibiotic resistance and genes for the Omp family, mobile genetic elements and type III effector protein and conserved hypothetical and adhesion protein. All three mutants may be involved in HGT and contribute to the evolution of Pph pathogenesis. Thirty five Pseudomonas strains were examined for their conjugation and transformation ability. Results showed two Pph strains Pph 882 (race 2) and Pph 1375A (race 5) have transformation ability and 28 Pseudomonas strains have conjugation ability. However, during this study transformation ability of Pph 1448A appeared to be lost. Examination of the loss of competence in Pph 1448A showed two changes i.e. growth rate reduction in vitro in LB liquid media and plasmid genome alteration by bean pod passage. Plants and bacteria can interact with one another in a variety of different ways. The interaction may be beneficial, harmful or neutral for the plant. This work has contributed to the understanding of these interactions between Pph 1302A and Pph 1448A in their host plants. These may allow subsequent development of sustainable disease control strategies.

Mixed perennial ryegrass white clover (WC) swards (GWc) provide a sustainable nitrogen source for grazing systems and improve herbage quality, but sward WC content and nitrogen fixation can be suppressed by fertiliser nitrogen application. Differences in structural characteristics between the species can affect dairy cow digestion process and performance. In this thesis aspects related to the effect of nitrogen fertilizer application on intensively grazed GWc and grass only swards (GO) and the effects of grazing both swards on dairy cow feeding behaviour, herbage depletion rate, rumen function, methane emissions and milk production were investigated. Regardless of nitrogen rate applied (rates up to 240 kg N/ha we applied), WC inclusion into grass wards increased herbage production, quality and nitrogen yield. These effects declined as nitrogen rate increased, due to a reduction in WC content and fixation, but less so below 120 kg N/ha. When cows rotationally grazed either a GO or GWc, both swards had similar herbage production, but GWc had slightly greater herbage quality. Sward WC contents were approximately 20%, yet cows had similar milk production and composition. Cow daily and per unit of output methane emissions were similar, but cows grazing GWc had lower methane emissions per unit of feed intake. Although cows in both groups grazed for similar times, the cows on GWc spent less time ruminating, especially in summer and autumn. Rumen volatile fatty acids were similar on both swards but isoacids and D-lactic acid percentages, ammonia content and rumen pH were higher in autumn for cows grazing GWc. Similar sward depletion rates were observed. Overall, WC related effects were more likely to occur from June onwards, when sward WC content was greatest.

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Climate change has been projected to significantly affect agricultural productivity and hence food availability during the 21st century, with particularly negative effects across the global tropics. However, the uncertainty associated with projecting climate change impacts is a barrier to agricultural adaptation. The work reported in this thesis is a contribution to the understanding of genotypic adaptation to near-term (i.e. 2030s) climate change and many of the associated uncertainties, using model ensembles. This work focuses on Indian groundnut and uses the General Large Area Model for annual crops (GLAM) and the EcoCrop niche model to investigate the response of groundnut under future climate scenarios, and to develop a genotypic adaptation strategy. Under the future representative concentrations pathway (RCP) 4.5, robust positive climate change impacts on crop productivity were found in 3 (western, northern and south-eastern) out of 5 groundnut growing regions. From the remainder of regions, one presented robust negative impacts and in the other uncertainties precluded a robust statement being made about productivity changes. Yield gains were associated with seasonal precipitation increases, a lower frequency of occurrence of terminal drought and its effect on cropping season length. Yield loss in central India was associated with less radiation interception and reductions in crop duration, whereas in the south there was large uncertainty due to temperature biases in GCMs triggering (or not) heat stress during anthesis. The latter result suggests that decisions of whether to correct or not GCM biases and the method of correction may be at least as important as the choice of climate scenario, or the choice of crop model parameters. Adaptation simulations indicated that the most critical traits for groundnut adaptation under future scenarios are increases in maximum photosynthetic rates, greater partitioning to seeds and, where enough soil moisture is available, also increases in the maximum transpiration rate. Changes to crop duration were beneficial if durations did not exceed those of the baseline, and hence allowed for enough water uptake at the end of the cropping season. Yield gains in adaptation scenarios were particularly large in eastern and northern India, and more moderate across the rest of the country.

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Callosobruchus maculatus (Fab.) is a beetle belonging to the family Bruchidae. The beetle is a serious economic pest of stored legumes in the tropics and subtropics. C. maculatus has been chosen for this study because it shows contrasting larval competition and oviposition strategies. Competition has been described in terms of the Avoid-Attack dichotomy (Smith and Lessells 1985). Research has been carried out to determine the Mendelian inheritance of larval competition and oviposition in the black Brazil and Yemen strains of Callosobruchus maculatus. The initial results were inconclusive because there was no significant (p 0.05) difference in the pattern of emergence between the Yemen and Brazil stains. Therefore, the experiments were repeated using the South India and Brazil strains. The results of the F1 generation were similar to results obtained by other workers (Messina 1991 and Toquenaga et al 1994), but the results of the F2 generation resembled the expected results for a single gene model in which Avoid behaviour was dominant, though the results were not clear cut. It was desirable to determine the inheritance of competition and oviposition to determine if evolution was acting on autosomal loci or a suite of genes. The cost of exploitation competition (E) was also estimated, using a method described by Colegrave (1995). The cost of passive exploitation has been described by Smith and Lessells (1985) and Smith (1990) and is a major determinant of the evolution of competition strategies in Callosobruchus maculatus. The Yemen, Brazil and South India strains were used in these experiments and experiments were conducted on three seed types. E 0.5 for all stains on the cowpea and adzuki beans but for the South India strain on mung E 0.5 and this may explain why Attack behaviour exists in the South India strain Finally the theoretical prediction of Smith and Lessells (1985), that competition evolves under frequency dependent selection, was tested by ratio experiments. These experiments demonstrated that selection was dependent upon the initial frequencies of the phenotypes in the population because populations that had an initial frequency of 30% Brazil or greater appeared to moving towards fixation of Avoid.

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