Masters Degrees (Plant Sciences)
Permanent URI for this collection
Browse
Browsing Masters Degrees (Plant Sciences) by Subject "AFLP"
Now showing 1 - 3 of 3
Results Per Page
Sort Options
Item Open Access Genetic variation in Clivia miniata var. citrina(University of the Free State, 2006-06) Gagiano, Anthia; Spies, J. J.; Herselman, L.; Herselman, L.English: The genus Clivia is from the African tribe Haemanthaceae and a member of the family Amaryllidaceae. Clivia is endemic to southern Africa. Yellow Clivia are mutations of the orange-red standard forms that have appeared spontaneously in both wild and garden populations. Yellow Clivia plants are rare and desirable and were described as Clivia miniata var. citrina. Hobbyists from around the world trade in these ornamental plants initiating entire enterprises. Although the yellow form occurs naturally, many yellow clones have arisen through cultivation. Clones passed on from breeder to breeder have acquired different names. For directed breeding purposes in a thriving industry it is important to identify genetically similar plants. The aims of this study were to evaluate existing microsatellites for Clivia miniata var. citrina, to determine if AFLP analysis can distinguish among different plants within the genus Clivia and to determine genetic relatedness between different plants of ‘Vico’, ‘Giddy’ and ‘Natal Yellow’ cultivars. Previous studies done on Clivia include RAPD analysis and SSR analysis for Clivia. Work done in this study presents a first report of AFLP and SSR fingerprint analyses on C. miniata var. citrina. SSR fingerprint analysis revealed that the existing four SSR primer combinations were not applicable for studies on C. miniata var. citrina. AFLP analysis was optimised using a total of 28 EcoRI / MseI primer combinations. Primer combinations were evaluated using six randomly selected Clivia plants based on number of generated fragments, ability to score generated fragments, ability to detect polymorphism and level of polymorphic fragments. Fragments generated using EcoRI+3 primers in combination with Mse+4 primer combinations conformed to the chosen criteria. Primer combinations E-ACC with M-CATC, E-AGC with M-CATC and E-AGC with M-CTGG were selected for further studies on Clivia. AFLP analysis using three preselected primer combinations on 72 Clivia plants was successful in detecting genetic diversity and determining genetic relationships within closely related cultivated Clivia plants. Relatively high levels of genetic diversity (35%), as expected from known pedigree and species data, existed among Clivia plants. Genetic diversity within C. miniata and C. miniata var. citrina plants was high at 27%. Plants available for scrutiny were all genetically distinct. However, based on known pedigree data, names allocated to plants might not be truly representative of the true origin of the plants (e.g. Vico Meristem plants). Material obtained from different breeders could be distinguished at DNA level (e.g. ‘Giddy’ and ‘Natal Yellow’ cultivars). AFLP analysis revealed that different flower coloured plants (Apricot, Blush, Peach, Orange and Yellow) as well as plants from the same geographic areas were distributed together throughout the dendrogram with only a few of a certain colour grouping together. Known Group 1 Yellow and Group 2 Yellow were also present throughout the entire dendrogram, although the majority of known Group 1 Yellow plants grouped together. Clustering of the different species of the genus Clivia agreed with known pedigree data and hybrids included with their parents clustered according to known pedigree data. The phylogenetic relationships of natural populations of C. miniata indicated that all C. miniata plants shared a common ancestor. Clivia miniata from the same geographical area grouped together in the cladogram. More data would be required to prove these observations for all Clivia. Taxonomic status of the C. miniata var. citrina would depend on the monophyly of yellow Clivia plants. Orange flowered forms should be included to determine the validity of the current taxonomic status of these groups.Item Open Access The improvement of leaf rust resistance in selected bread wheat lines(University of the Free State, 2002-11) Craven, Maryke; Pretorius, Z. A.; Labuschagne, M. T.; Prins, R.English: The objective of this study was not only to improve leaf rust (caused by Puccinia triticina) resistance in selected wheats (Triticum aestivum L.), but to focus on durability as well as agronomic acceptability of resistant lines. This was achieved by traditional breeding techniques as well as with the use of AFLP analysis. Seven bread wheat lines were obtained from ARC-Small Grain Institute (SGI) where they were developed. Six leaf rust resistance sources were obtained from the University of the Free State. The breeding strategy focused on creating lines that contained both seedling and adult plant resistance genes. Lr34 was chosen as the adult plant resistance source as it is an important gene due to its durability and interaction with other leaf rust resistance genes. It is also an easy gene to follow as it is associated with leaf tip necrosis. In an attempt to create genotypes that will remain durable, four seedling leaf rust resistance genes (Lr21, Lr32, Lr36 and Lr41) were each combined with Lr34 in the seven SGI backgrounds. By combining seedling and adult plant genes, and selecting only the lowest infection types throughout all phases of testing, a significant shift in the leaf rust resistance of the population occurred. Greenhouse evaluations of plant architecture and agronomic performance of lines containing both a seedling gene and Lr34, indicated that individual plants, similar or better than the original SGI parent, had been selected. Several of these selections can therefore be incorporated in larger, mainstream breeding programmes. It is, however, imperative that the agronomic and quality value of selections be determined under field conditions. More efficient manipulation of an undesignated Lr gene was also attempted. This gene, which originates from T. monococcum, was incorporated in certain bread wheat lines and cultivars. Since the gene is characterized by an immune response to South African pathotypes of leaf rust, it is considered valuable in terms of rust resistance. However, its single gene nature implies it will not remain durable and that it has to be protected in complex resistance gene combinations. To achieve this, linked molecular markers are needed. In this study a putative AFLP marker for leaf rust resistance was generated by S12/M14 and S12/M44 using pooled DNA. Analysis of individual plants from which the DNA bulks were constructed indicated that the marker might not be closely linked to the Lr gene of interest. Validation in three additional backgrounds revealed several instances of recombination between the marker and the gene, emphasising the need to do a proper linkage study. Should the linkage distance be acceptable, the marker might still be useful as it proved to be polymorphic in five different wheat backgrounds. The linkage distance is also needed before the intensive effort to clone and convert the AFLP band to a more user-friendly STS marker will be considered.Item Open Access Morphological and genetic characterisation of mango (Mangifera indica L.) varieties in Mozambique(University of the Free State, 2010-05) Mussane, Cecilia Ruth Bila; Van Biljon, A.; Herselman, L.English: Mango (Mangifera indica L.) belongs to the Anacardiaceae family. Consumption is increasing worldwide due its their nutritional value that is rich in vitamins A and C, potassium, β-carotene, fibre as well as proteins. Mangoes are economically important for Mozambique because of suitable climatic conditions and international market opportunities. This study compared morphological and AFLP characterisation of 30 mango varieties from the Umbeluzi research station, including some commercial varieties: “Keitt”, “Kent”, “Haden”, “Sensation” and “Ruby”. Morphological characterisation using IPGRI descriptors were divided into quantitative (23 characteristics) and qualitative (58 characteristics) data. The total variation was lower using quantitative (89.4% similarity) than qualitative data (60% similarity). The combined quantitative and qualitative dendrogram had 63% similarity and clustered varieties in three subgroups based on high fruit weight, high Brix content and low fruit weight. AFLP characterisation used seven primer combinations, generating 207 data points and detecting 74.9% polymorphism with an average of 30 fragments per primer combination. The total variation was low (72.49% similarity) and the dendrogram showed two main groups subdivided in five subgroups based on low fruit weight, dwarfness and low Brix content, high fruit weight and roundish fruit shape. The combined morphological and AFLP dendrogram was more accurate in clustering varieties based on geographic origin within the country and from outside. The dendrograms presented in the study will help breeders to select parents for crosses. PCA results confirmed the pattern of clustering of varieties based on fruit weight and Brix/acidity ratio. It is recommended to extend the study to include, the entire collection at Umbeluzi and to include morphological data, considering pest and diseases resistance characterisation, as well as genetic and cytological analysis. A study of genotype x environment interactions done over years should be undertaken in future.