| Přispěvatelé: |
Siebert, S.J., Cilliers, D.P., Van den Berg, J., 12204145 - Siebert, Stefan John (Supervisor), 12319724 - Van den Berg, Johann (Supervisor), 13077767 - Cilliers, Dirk Petrus (Supervisor), 12204145 - Siebert, Stefan John (Supervisor)||13077767 - Cilliers, Dirk Petrus (Supervisor)||12319724 - Van den Berg, Johann (Supervisor) |
| Popis: |
MSc (EnvironmentalSciences), North-West University, Potchefstroom Campus Sugarcane (Saccharum hybrids) belongs to the Andropogoneae in the Poaceae. The grass family is known to have provided the world’s most economically important crops. In assessing the risk of cultivating genetically modified (GM) grass crops in South Africa, gene flow studies have to be conducted prior to the approval or release of such crops into the environment as hybridisation may occur between crop plants and wild relatives if certain barriers to gene flow are crossed. The aim of the study was to conduct a spatial assessment of Saccharum and its relatives in eastern South Africa and to assess potential gene flow, which in turn will inform the way forward for risk assessments. Eleven Saccharum wild relative species were selected for analyses based on their presence in the sugar producing region of South Africa: four species in the Saccharinae and seven in the Sorghinae. Spatial, temporal and gene flow assessments of wild relatives were conducted: prevalence, spatial overlap, proximity, dispersal potential, flowering times, hybridisation potential and relatedness. Field surveys, herbarium distribution records and literature were used to assess these factors and to determine the gene flow likelihood. A total of 815 herbarium specimens were sourced from 11 suitable herbaria and they were supplemented by 34 observations during field visits to sugarcane cultivation areas. The presence of all target species was confirmed in sugarcane areas. Imperata cylindrica (L.) Raeusch., Sorghum arundinaceum (Desv.) Stapf and Miscanthidium capense (Nees) Mabb. scored the highest likelihood for prevalence, flowering time and spatial overlap with sugarcane. Although I. cylindrica and S. arundinaceum generally ranked the highest for spatial and temporal assessments, they were not important candidates for gene flow potential from sugarcane, since they were not considered as reproductively compatible due to their low scoring on the relatedness assessment. Cleistachne sorghoides Benth., Miscanthidium capense, Miscanthidium junceum (Stapf) Pilg.and Sarga versicolor (Andersson) Spangler scored higher as close relatives of sugarcane in the study area. Miscanthidium species ranked highest for gene flow potential and were the only target species that were flagged by this study as having a high likelihood for gene flow with sugarcane. This is supported by the more recent divergent age from sugarcane that falls within the period considered to be optimal for hybridisation within Saccharinae species. When considering the likelihood scores of all species, the regions with the highest likelihood for gene flow were associated with coastal and southern-inland KwaZulu-Natal. These areas should be avoided when cultivating GM sugarcane should it be approved in the future, or in-depth risk assessments should be conducted before release. This study recommends that future studies be done to assess pollen compatibility and viability for sugarcane and related species (Miscanthidium capense and M. junceum) as part of a risk assessment, as some gene flow barriers, such as proximity and flowering time, was shown to be crossed in this study. Masters |
