Doctoral Degrees (Plant Sciences)

Permanent URI for this collection

http://hdl.handle.net/11660/458

Browse

Browsing Doctoral Degrees (Plant Sciences) by Subject "AFLP"

Now showing 1 - 4 of 4
  • Thumbnail Image
    ItemOpen Access
    Biodiversity in plant, grain and nutritional characteristics of sorghum [Sorghum bicolor (L.) Moench] accessions from Ethiopia and South Africa
    (University of the Free State, 2010-11) Gerrano, Abe Shegro; Labuschagne, M. T.; Geleta, N.; Van Biljon, A.
    This study was conducted with the objectives of assessing the genetic diversity of sorghum accessions that were obtained from different geographical locations in Ethiopia, as well as South Africa, using phenotypic traits, AFLP markers, minerals, starch and protein. Twenty phenotypic traits were subjected to ANOVA and highly significant differences were observed for all traits among accessions. Some important characteristics were found to be significantly correlated, which could allow for selection of related secondary characteristics to improve primary characteristics. Cluster analysis grouped accessions into five clusters based on similarity. These results would be useful in a breeding programme for selecting sorghum accessions to improve production. Nine qualitative morphological traits were also analysed using the Shannon Weaver diversity index (H’). The results showed that the average H’ was 0.59. The highest polymorphism was recorded for the glume colour (0.84), while the lowest was recorded in panicle compactness and shape (0.31). This indicated that there was wide variability among accessions studied. The cluster analysis for the qualitative traits also identified accessions based on their similarity and differences based on their genetic distances. Hence, visual selection and measurements of the sorghum attributes in field trials could be used to select the desirable traits and improving yield and stability of the accessions in breeding programmes. AFLP analysis showed high genetic similarity of Ethiopian landraces, as well as breeding material from the Ethiopian and South African sorghum breeding programmes, even though the phenotypical characterisation showed high variability. This indicated the possibility that South African and Ethiopian breeding material may have a common ancestry. The morphological, AFLP and combined morphological and AFLP cluster analysis clearly distinguished between all accessions, even though they were genetically similar. Sorghum kernels were used to determine the mineral, starch and protein composition of the sorghum accessions. The ANOVA of the traits revealed highly significant variation among the accessions studied. Furthermore, PCA grouped accessions according to their similarity/differences in the four quadrants which confirmed that there was variation among them for these nutritional traits. Therefore, there would be potential for selecting accessions for specific mineral and protein content for human consumption, and specific starch and amylose content for industrial use. The sugar content of the stalks also indicated the potential to develop dual sorghum cultivars where both the seed and sugar can be produced from the same plants.
  • Thumbnail Image
    ItemOpen Access
    Breeding potential of cassava (Manihot esculenta Crantz) in Mozambique
    (University of the Free State, 2008-05) Da Silva, Anabela Matangue Zacarias; Koen, Elizma; Kanju, Edward Eneah
    English: This study represents the first comprehensive genetic study based on local cultivars of Mozambique. Five cassava (Manihot esculenta Crantz) parents were crossed in a full diallel. The parents and F1 progeny were evaluated for eight agronomical and 17 morphological traits in two consecutive seasons. General combining ability (GCA) was higher than specific combining ability (SCA) for number of roots, root taste, fresh root yield, root pulp hardness and harvest index. Positive heterosis was seen for number of roots, fresh root weight and harvest index. Negative heterosis was present for cassava brown streak virus disease. Harvest index showed high broad sense heritability, which indicated that phenotypic variance was additive. The predictability ratio was close to unity, which confirmed that this trait is highly heritable, and determined by additive gene action. Cassava brown streak root necrosis had SCA effects significantly higher than GCA effects indicating the presence of non-additive genetic effects. A selection index comprised of the most relevant characters was compiled. Amplified fragment length polymorphism (AFLP) analysis showed high genetic similarity among 17 accessions. A total of 425 fragments were produced by eight primer combinations. Mocuba and Nikwaha were the most distinct among the accession and two heterotic groups were suggested. Morphological analysis showed genetic distance ranging from 0.105 to 0.833. The correlation coefficient between AFLP and agronomic clustering was not significant. The AFLP and morphological analysis did not group the accessions according to geographical origin. The principal component analysis provided diversity structure, suggesting the effectiveness of this analysis in genetic diversity studies. The narrow genetic similarity observed, indicates the need to introduce new cassava germplasm.
  • Thumbnail Image
    ItemOpen Access
    Characterisation and diallel analysis of commercially planted cotton (Gossypium hirsutum L.) germplasm in Tanzania
    (University of the Free State, 2005-11) Lukonge, Everina Paul; Labuschagne, M. T.; Herselman, L.
    English: 1. Thirty cotton varieties were studied. Seven parents generated 21 F1 diallel progenies. The main objective was to evaluate genotypes through oil content, fatty acids, morphological and molecular characteristics. Statistical procedures were performed with Agrobase, NCSS and NTYSS computer programmes. Correlation, heterosis, heritability, G x E interaction and stability values were obtained. Stability across four environments was analysed by five stability measures, that of Shukla, Wricke, Lin and Binns, Eberhart and Russell and the AMMI analysis. 2. Significant differences were observed for oil and fatty acids content. Oil content results revealed an average of 20.23%. The ratio for polyunsaturated:saturated fatty acid was 2:1 and for unsaturated:saturated 3:1. The predominant fatty acids were linoleic, palmitic, oleic, stearic, myristic, palmitoleic, arachidic and behenic. Palmitic fatty acid was high while oleic and stearic fatty acids were low for almost all varieties studied. Oil and fatty acid content were significantly influenced by the environment. CIM 70 and Cyto 12/74 can be selected as parents for increased oleic and stearic fatty acid and Stoneville 506 as a parent for reduced palmitic fatty acid, increased oleic, stearic and linolenic fatty acids in hybridisation. 3. ANOVA results indicated significant differences between varieties for all agronomical characteristics studied, where NTA 93-21 and NTA 93-15 were the best performers almost for all characteristics. Genetic distances for morphological (qualitative characteristics) analysis ranged from 0.18 to 0.80. Two major groups, one including many varieties from Africa and the other including varieties from the USA, were revealed. 4. AFLP analysis showed high genetic similarities (0.85 to 0.98). Varieties were distinguished according to pedigree and origin. The increased genetic similarity observed, indicates the need for the introduction of more diverse cotton material. Comparison of agronomical and AFLP markers for determining genetic diversity indicated that genetic similarities between varieties were low for agronomical compared to AFLP markers. The correlation coefficient between AFLP analysis and agronomical genetic similarities was not significant, 5. Highly significant differences between genotypes over environments were observed and NTA 93-21 crosses outperformed the seven parents for almost all characteristics. The parent Okra leaf performed poorly for many characteristics. Trial sites Ukiriguru followed by Kanziga were high yielding environments. 6. Combining ability analysis results indicated significant variation in GCA estimates among parents for different characteristics. Genotypes having high positive GCA estimates for yield components exhibited negative GCA estimates for fibre quality, excluding NTA 93-21. Some combinations indicated positive and significant SCA effects for seedcotton, boll weight, GOT and lint yield. The GCA/SCA ratios for most of the studied characteristics were larger than one. 7. Correlation among characteristics indicated highly significant positive and negative correlations. The observed high and significant GCA and SCA effects for those characteristics are promising for cotton population improvement. Positive heterosis for boll weight was observed for more than 90% of the combinations. Hybrids with high SCA values presented high values of heterosis. Heritability values for the studied characteristics were moderate to high. 8. The combined ANOVA over four environments indicated significant differences between genotypes and locations for all characteristics. The percentage contribution of location to total variation was high compared to genotype variation except for a few characteristics. Highly significant differences of G x E for lint yield and fibre strength were observed. 9. Three stability procedures (Wricke, Shukla and ASV) identified similar stable genotypes. Eberhart and Russell’s procedure, was in harmony with the above three methods but with some divergence. Cultivar superiority measure deviated from the other four measures. Therefore the procedures of Wricke, Shukla and AMMI can be applied for cotton stability studies.
  • Thumbnail Image
    ItemOpen Access
    Characterization of cactus pear germplasm in South Africa
    (University of the Free State, 2007-05) Mashope, Barbara Keitumetse; Labuschagne, M. T.; Swart, W. J.; Herselman, L.
    English: South Africa hosts one of the largest cactus pear germplasm collections in the world. However, not all the varieties have been fully characterised, and evaluated for fruit quality, nutritional quality for use as fodder, and disease resistance. In this study, 38 South African cactus pear (Opuntia ssp.) varieties were characterised using AFLP markers to circumvent G X E effect on phenotypic characterisation. With the use of nine primer combinations, the varieties were grouped into four main clusters based on 346 fragments (per sample) of which 48% were polymorphic between samples. The dendrograms generated indicated that commercially cultivated varieties were dispersed amongst the different clusters indicating that they represent the genetic diversity within the germplasm. Genotype specific fragments were generated using six primer combinations, allowing the unique identification of nine varieties, three of which are commercially cultivated (Meyers, Roedtan, and Santa Rosa). Varieties that are recommended for commercial cultivation in the Mokopane district of the Limpopo Province, based on fruit quality and yield are Gymno Carpo, Malta, Algerian, Morado, Meyers, and Roedtan. These varieties meet the minimum requirements for cactus pear fruit production in South Africa. Nutritional quality evaluation of pruned cladodes from a commercial orchard in the Free State Province indicated that the varieties, Malta, Gymno Carpo, and American Giant ranked the highest in terms of CP content. Varieties that yielded the highest DM content were Messina, Nepgen, and Cross X. Varieties that ranked the highest for OM content were Cross X, Nepgen, and Sicilian Indian Fig. Gymno Carpo and Malta are amongst the varieties recommended for cultivation for fruit, as such they can be used as dual purpose crops for the production of both fodder and fruit. Evaluation for disease resistance indicated a quantitative mode of resistance across all varieties for all three fungal pathogens tested. The most resistant varieties surveyed in this study across all three fungal pathogens were Amersfoort, Meyers, and Algerian. Roly Poly, Direkteur, and Zastron were the more susceptible varieties. Of the three fungal pathogens tested, P. virens was the least affected by the antagonistic activity of the yeast isolates. Isolate 25 (Rhodotorula mucilaginosa) performed well against all three pathogens, whilst the remainder of the isolates displayed inhibition at varying degrees.