PhD (2017) and B.Ag.Sci. Honours (2011)
PhD Research Overview
Aspects of soil ecology of rhizobia affecting nodule occupancy on lucerne and white clover (PDF 18.2 MB)
Successful establishment of white clover (Trifolium repens) and lucerne (Medicago sativa) in the field depends on the formation of effective symbioses with Rhizobium leguminosarum and Sinorhizobium meliloti, respectively. High numbers of naturalised rhizobia and the poor persistence of commercial inoculants has cast doubt on the need for commercial inoculation in New Zealand. Kathryn’s thesis investigated aspects of the soil ecology of R. leguminosarum and S. meliloti that affected the persistence and success of applied strains. Overall, this research has highlighted differences in the success of the commercial inoculants R. leguminosarum and S. meliloti, as measured by nodule occupancy. For R. leguminosarum, strains better able to utilise common rhizosphere exudates were competitive for nodule occupancy. For S. meliloti, results showed that there was potential to select strains better able to drive nodulation of lucerne in the harsh New Zealand high country soils. Thus, the new tools and knowledge generated in this thesis have identified key traits for better selection of commercial inoculants.
Prof. Derrick Moot and Dr Hayley Ridgway with Dr Steve Wakelin (AgResearch) supervised Kathryn’s PhD project.
B.Ag.Sci. Honours Research Overview
Lucerne (Medicago sativa L.) establishment after inoculation with different carriers of Ensifer meliloti on five sowing dates (PDF 1.6 MB)
Kathryn worked on lucerne inoculation with Masters student Qakathekile Khumalo. At Ashley Dene she established a range of lucerne stands at different sowing dates to modified soil moisture conditions at sowing. Lucerne was then established with one of three different rhizobia carriers to see if crop growth and development and/or rhizobia efficacy was affected. DNA was extracted from lucerne nodules of the field grown plants to identify and characterise the bacteria and rhizobia inhabiting the nodules. Kathryn was supervised by Prof. Derrick Moot.