Plant Sciences

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Open Access
A taxonomic study of the genus cryptolepis (periplocoideae: apocynaceae)
(University of the Free State, 2013) Joubert, Lize; Venter, A. M.; Venter, H. J. T.; Bruyns, P. V.
Cryptolepis R.Br. (Apocynaceae, Periplocoideae) was taxonomically revised. Detailed descriptions of macro and micro-morphology, palynology, geographic distribution and ecological characteristics were presented. An identification key to the species was compiled and the nomenclature of all species was revised while all available type material was studied and lectotypes and neotypes were designated where necessary. Molecular phylogenetic analyses, based on the gene regions ITS, trnD–T and trnT–F, of representative species of 28 periplocoid genera and 22 Cryptolepis species were presented and the monophyly of Cryptolepis was evaluated. Historically a total of 81 species names and four subspecies names were published for Cryptolepis. However, a large number of species names were later placed in synonymy or transferred to other genera, while several new combinations were published. This resulted in a total of 29 accepted Cryptolepis species at the commencement of this study. Three new species, C. ibayana, C. thulinii and C. villosa, resulted from this study and the latter two were described in this thesis. One species, C. producta, was synonymised with C. oblongifolia. Cryptolepis, therefore, comprises a total of 31 species at present. In terms of species diversity, distribution and potential pharmaceutical and economic value, Cryptolepis is one of the most significant genera in the Periplocoideae. Cryptolepis grows throughout sub-Saharan Africa, the southern parts of Yemen, the island archipelago of Socotra, and southern Asia ranging from India to southern China, Taiwan, the Philippines and Indonesia. Most of the species grow in tropical forests or savannah, but 13 species are also adapted to arid environments. The majority of Cryptolepis species are concentrated in four centres of diversity along the east coast of Africa and on Socotra. These hotspots are associated with both arid and forest refugia in areas which have been regarded as local centres of endemism for a number of other plant taxa. The phylogenetic analysis of Cryptolepis indicates that most of these hotspots were colonized repeatedly by different Cryptolepis groups. In addition to the influence of climate shifts, edaphic conditions and also fire had a significant influence on species diversity and distribution in Cryptolepis. Macro and micro-morphological investigations indicated that numerous characters, including growth form, leaf shape and size, leaf epidermal characters, venation, inflorescence structure, floral structure and seed coat surface characters, are of diagnostic value at species level in Cryptolepis. However, the species can only be accurately identified by using a combination of these characters. The molecular phylogenetic analyses revealed that Cryptolepis is paraphyletic and, in order to establish a monophyletic genus, it was proposed that the circumscription of the genus be broadened to include Parquetina as a synonym of Cryptolepis. Several vegetative and reproductive characters showed a high degree of homoplasy, suggesting a high degree of morphological plasticity. This plasticity was also found at species level in C. oblongifolia, which showed significant variation in vegetative and reproductive features. This, together with a high tolerance for disturbance, has resulted in C. oblongifolia becoming the most widely distributed of all Cryptolepis species.
Open Access
The ability of a novel compound to enhance the effect of urea on nitrogen deficient tomatoes
(University of the Free State, 2012-03-22) Pretorius, Hendri; Potgieter, G. P.
English: A company, Elementol (Pty) Ltd, requested the evaluation of their novel product, Pheroids. Pheroids can apparently facilitate the transport of phytological beneficial substances over membranes. Information regarding the chemical attributes was withheld as patent registration is still pending. Pheroids is apparently a microemulsion containing free fatty acids (FFA’s) and or fatty acid derivatives. It apparently encapsulates a substance and facilitates its transport over the membrane. The exact mechanism involving encapsulation, transport and release of the substances inside the cells is still vague due to little information available on it. The aim of this study was to evaluate the ability of Pheroids to facilitate the transport of additional nitrogen, urea in this case, in tomatoes grown under nitrogen limiting conditions. Tomatoes (Lycopersicon esculentum cv. Rodade Star) were cultivated in a greenhouse using a circulating ebb and flow hydroponic setup, which supplied the plants with either a control- or nitrogen limiting nutrient solutions. The plants cultivated in the nitrogen limiting conditions showed a remarkable reduction in vegetative development and yield. To alleviate the effect of nitrogen limiting conditions on yield, the plants were foliarly sprayed with 0.5% and 1% urea solutions, singly or mixed with Pheroids, once every two weeks. The purpose of these foliar treatments was to determine whether Pheroids can further enhance the absorption and transport of urea across membranes of the leaves to alleviate the effect of limiting nitrogen supply. Plants grown under nitrogen adequate conditions (control) were also foliarly treated with a 0.5% urea solution, singly and mixed with Pheroids, to determine to which extent control plants react to the additional nitrogen supplied. The reduction in yield, as a result of limited nitrogen supply, was partially alleviated by spraying nitrogen deficient plants with the 0.5% and 1% urea solutions. However, mixing the 0.5% and 1% urea solutions with Pheroids, not only improved vegetative growth and generative development, but also improved yield, suggesting that Pheroids indeed has the ability to improve the uptake of urea. The 0.5% urea / Pheroids solution specifically proved to have the best ability in alleviating the effect of nitrogen limiting conditions on yield without compromising fruit quality. Although the reducing effect was not completely alleviated, the yield and loss in income as a result of nitrogen limiting conditions was prevented to a large extent. Spraying control plants with 0.5% urea, singly or mixed with Pheroids, also improved yield, without compromising fruit quality. In addition, Pheroids itself, without mixing it with any substance, also resulted in increased yields in both control- and plants grown under nitrogen limiting conditions. In summary, it appeared that Pheroids has the ability to facilitate the transport of phytological beneficial substances, in this case urea, over plant membranes and enhances cellular nitrogen content, but this needs further detailed analyses. This phenomenon was more evident in plants grown under nitrogen limiting conditions than in plants grown under control conditions. Taking into consideration that most crops frequently may suffer from nitrogen limiting conditions in standard agricultural practices, Pheroids may have numerous potential applications in the agricultural industry.
Open Access
Abiotic stress tolerance and nutritional traits of newly developed quality protein maize hybrids in sub-Saharan Africa
(University of the Free State, 2022) Engida, Bitew Tilahun; Labuschagne, M. T.; Terekegn, A.; Van Biljon, A.; Wegary, D.
Drought and poor soil fertility are some of the most serious maize production challenges in sub-Saharan Africa (SSA). Identification and development of quality protein maize (QPM) cultivars that have high yield potential and tolerance to these stresses is a reliable and affordable option to improve food security and malnutrition problems in the region, especially for small scale farming communities. Although several stress tolerant maize varieties have been released and disseminated for commercial production in SSA so far, limited development and release of stress tolerant and high yielding QPM varieties compared to normal maize varieties is evident. Limited attention has also been given to the development of nutritionally enriched varieties compared to grain yield improvement. Therefore, the main goal of this study was to study 40 newly developed QPM hybrids obtained from the International Maize and Wheat Improvement Center (CIMMYT) – Zimbabwe, under stressed and non-stressed environments to allow selection of QPM hybrids that could outperform the existing commercial QPM and normal maize cultivars with respect to grain yield and concentrations of tryptophan, iron (Fe), zinc (Zn) and molar ratios of Fe and Zn to phytic acid. The specific objectives were: (1) to determine variability and performance of QPM hybrids for grain yield and agronomic traits under stressed and non-stressed environments, (2) to determine tryptophan, Zn and Fe concentrations, and molar ratios of Zn and Fe to phytic acid in QPM hybrids grown under stressed and non-stressed environments, (3) to analyse genotype by environment interaction and grain yield stability of QPM hybrids and (4) to determine correlations among grain yield, agronomic and nutritional traits in QPM hybrids evaluated under stressed and non-stressed environments. Significant variation was seen for grain yield, and almost all studied agronomic and nutritional traits under stressed and non-stressed environments. Phenotypic coefficient of variation (PCV) was higher than genotypic coefficient of variation (GCV) for grain yield and all other agronomic and nutritional traits under all conditions, indicating that environment effect was higher than genotype effect on the expression of the traits under stressed and non-stressed environments. Broad sense heritability of grain yield was higher than 0.6 across all environments, with the exception of managed drought conditions. Anthesis silking interval (ASI) had relatively high GCV estimates and genetic advance, as a percentage of the mean, across all conditions. This indicated that the presence of sufficient genetic variability among genotypes can improve synchronization under different management conditions through selection. Grain yield was reduced by 47% under random stress, 68% under managed drought and 71% under low N conditions. Protein and tryptophan concentrations in the grain were decreased by 36.0% and 21% respectively under low N conditions and Fe and Zn concentration also decreased by 48% and 36% under low N stress and 63% and 9% under random stress, respectively. Some QPM hybrids showed better or comparable performance in terms of grain yield potential and nutritional quality traits compared with the best QPM and normal maize checks under different management conditions, indicating the genetic gain that has been made in the QPM breeding programme. Based on Additive Main effect and Multiplicative Interaction (AMMI) analysis and Genotype and Genotype by Environment interaction (GGE) biplot analysis entries 10 (CZH142238Q) and 14 (CZH15142Q) under optimum; 23 (CZH17192Q) under random stress; 19 (CZH17188Q) and 40 (CZH17209Q) under managed drought and 14 (CZH15142Q) under low N were the most stable and the highest yielding hybrids. Environments Kwekwe (KW), Bindura (BIN), Chokwe (CHO) and Bako (BK2) were identified as discriminating and representative sites for optimum conditions, random stress, managed drought and low N stress conditions, respectively, therefore these environments are promising for selecting well adapted genotypes in the respective management conditions. Grain yield was significant and positive correlated with number of ears per plant and negatively with days to anthesis and silking under low N stress. This confirmed the importance of these secondary traits in developing high yielding and early maturing genotypes. Grain yield was not significantly correlated with most of the nutritional quality traits under all management conditions, indicating a lack of common genes for simultaneous improvement of grain yield and these nutritional traits. Significant and positive correlations were observed between Fe and Zn under low N and random stress conditions.
Open Access
Adult-plant resistance to Puccinia recondita f. sp. tritici in a collection of wild Triticum species
(University of the Free State, 1999-05) Barnard, Johanna Elizabeth; Pretorius, Z. A.; Kloppers, F. J.
English: The ability of rust pathogens to mutate and form new and virulent races, necessitates the broadening of the genetic base of resistance in common wheat to rust diseases. The wild relatives offer a rich reservoir of resistance genes. In an attempt to identify new sources of resistance to Puccinia recondita f. sp. tritici, 353 Triticum accessions, comprising diploid, tetraploid and hexaploid species were evaluated for seedling and adult-plant resistance to a mixture of pathotypes UVPrt2, 3, 9, and 13. In addition to infection type studies, plant height, growth habit and head type of adult plants were also recorded. One hundred and twenty six of the accessions were resistant to moderately resistant as seedlings to the pathotype mixture, whereas 180 were resistant or moderately resistant as adult plants. The number of days from planting to flag leaf stage varied from 54 to 187. High levels of resistance were observed in adult plants of T. longissimum, T. sharonense, T. searsii and T. turgidum ssp. compactum. Triticum kotschyi and T. ventricosum expressed hypersensitive infection types. Partial resistance (small pustules without any apparent chlorosis), was observed in T. turgidum ssp. durum, T. turgidum ssp. pyramidale and T. tauschii. In T. turgidum, which comprised 14 subspecies and 272 accessions, approximately 44% of the adult plants were resistant to moderately resistant compared to 24% of the seedlings. According to these results 13 accessions, producing smaller or fewer leaf rust pustules, without the characteristic chlorosis and necrosis associated with hypersensitive resistance, were selected. Adult plants were quantitatively inoculated with pathotype UVPrt13 of P. recondita f. sp. tritici. Palmiet, a bread wheat cultivar susceptible to UVPrt13, was included as a control. Latent period of leaf rust, uredium size and density, and infection type were determined in two experiments. In the first experiment latent period ranged from 309 h to 401 h compared to 258 h in the susceptible control, Palmiet. In the second experiment Palmiet had a latent period of 244 h whereas those in the Triticum accessions ranged between 175 hand 372 h. Most accessions supported more uredia per ern" flag leaf surface than Palmiet in the first, but not in the second experiment. However, pustules were significantly smaller on most of the lines. Based on these components, T. timopheevii ssp. araraticum v. tumanianii, T. turgidum ssp. durum v. obscurum, and T. turgidum ssp. persicum v. stramineum, showed high levels of partial resistance. Triticum turgidum and T. timopheevii accessions rated as potentially valuable sources of resistance were selected for histological studies on mechanisms of resistance. Penetration and establishment of the leaf rust pathogen were studied in flag leaves of T. timopheevii, T. turgidum ssp. dicoccum, T. turgidum ssp. durum and T. turgidum ssp. compactum. The T. aestivum wheats Thatcher (Tc) (susceptible common wheat control) and TcLr19 (resistant common wheat control) were included in the experiment. Using fluorescence microscopy, infection sites of pathotype UVPrt13 were examined for the percentage prestomatal exclusion (germtubes not forming appressoria and appressoria not forming over stomata), abortive penetration (non penetrating appressoria and aborted substomatal vesicles), early abortion (six or less haustorium mother cells per infection site) and infection sites successfully culminating in colonies. Flag leaf sections were prepared for phase-contrast microscopy by staining with either Trypan blue alone or in combination with a solution of picric acid in methyl salicylate. To confirm and expand light microscopy observations, upper and inner surfaces of epidermal tissue of T. timopheevii and T. turgidum ssp. dicoccum were fixed and prepared for scanning electron microscopy. Observations showed that resistance in T. timopheevii was typically hypersensitive and may thus not be durable. The prehaustorial resistance exhibited in T. turgidum ssp. durum and T. turgidum ssp. compactum, may be valuable sources of nonhypersensitive resistance when transferred to cultivated wheat.
Open Access
Agronomic performance, consumer acceptability and nutrient content of new sweet potato varieties in South Africa
(University of the Free State, 2010-05) Laurie, Sunette Marlize; Labuschagne, M. T.; Faber, Mieke; Van Jaarsveld, Paul
English: Malnutrition, including vitamin A deficiency, and food insecurity are national priorities in South Africa. Sweet potato has several agronomic advantages giving it potential to address both priorities. The crop is popular amongst resource-poor farmers as it is easy-to-grow and hardy. Orange-fleshed genotypes (β-carotene-rich) are used internationally in crop-based approaches to address vitamin A deficiency. Due to a shortage of varieties with desirable traits for resourcepoor farmers, several new varieties have been developed. The overall objective of this study was to evaluate the agronomic performance, sensory quality and nutrient content of new South African varieties. The ANOVA of new varieties in MET, indicated significant differences in dry matter content, marketable yield, number of marketable roots and total yield. AMMI and GGE biplot analysis showed that cream-fleshed varieties Ndou and Lethlabula produced yields comparable to the commercial variety Blesbok. Ndou (unstable high yield), Mokone and Monate (stable, average yields) and Amasi (moderately unstable, average yield) had dry matter content similar to the control variety Mafutha (known for sweet and dry taste). Recommending these new varieties will have a considerable yield advantage over Mafutha, with a possible impact on food security. From MET with nine orange-fleshed varieties the ANOVA and GGE SREG analysis indicated that Impilo produced stable, high yield and 2001-5-2 unstable, high yield. Both had average dry matter content. The two varieties offer a significant yield advantage above USA imports, previously recommended to address vitamin A deficiency. Orange-fleshed varieties produced significantly lower yield than cream-fleshed ones. Raw roots of nine orange-fleshed varieties, harvested from MET at four agro-geographical production sites, had an overall mean trans-β-carotene content of 5091 to 16456 μg/100 g. Resisto, Khano, 2001-5-2, W-119, Beauregard and 1999-1-7 exceeded 5500 μg/100 g β-carotene (breeding target). Dry matter content ranged from 23.1% (Impilo) to 28.7% (W-119). The content of six minerals was determined. Consumption of a boiled portion of 100 g raw root of all nine varieties can potentially contribute to ≥100% of the recommended intake for vitamin A, 21% of magnesium, 12% of zinc and 9% of iron for 4 to 8 year old children. CIE L* and a* color measurement of nine varieties with varying orange flesh color had the best correlations with total β-carotene content, and is a faster selection method. A mathematical function with natural logarithm (ln) transformation derived to predict total β-carotene content from color L*, predicted 91% of the values with >75% accuracy. The color and taste acceptability of boiled sweet potato of new varieties were evaluated in two experiments by grade 1 – 7 learners and adults in a BIBD using a 5-point hedonic scale. A trained panel found clear differences in the sensory attributes of the varieties. Cream to yelloworange varieties, Mafutha, Lethlabula and Phala had the highest consumer panel (n=190) scores, associated most with wateriness, discolor, graininess, gumminess, sweet potato-like flavor and instronforce. Orange-fleshed varieties Impilo, Excel, Resisto, 2001-5-2, Serolane and W-119, and cream-fleshed varieties Monate and Ndou were acceptable to the second consumer panel (n=216), mostly related to dry matter content, maltose content, sweet flavor, wateriness, discoloration and dark edges. High maltose and starch content were found in Ndou, Serolane, Resisto and Monate; while Blesbok, Impilo and 2001-5-2 had high fructose and glucose content. Orange-fleshed varieties were as acceptable as cream-fleshed varieties. The present study provides novel results on G x E analysis, comprehensive and systematic determination of nutrient content, consumer and sensory assessment of a considerable number of new cream to orange-flesh sweet potato varieties promoted in South Africa. Varieties Ndou, Mokone, Monate and Amasi were recommended to address food security; and Impilo and 2001- 5-2 to address vitamin A deficiency.
Open Access
Analyses of drought tolerance in durum wheat (Triticum turgidum var. durum) genotypes
(University of the Free State, 2003-03) Fekybelu, Solomon Kebede; Labuschagne, M. T.; Viljoen, C. D.
English: In order to identify yield components associated with drought tolerance in durum wheat and evaluate the performace of Ethiopian durum wheat genotypes, 26 durum wheat genotypes, from different agro-ecologies of Ethiopia were evaluated under simulated moisture stress conditions. Stress caused dramatic reductions in grain yield and harvest index. Yield was significantly correlated primarily with number of kernels per spike and 100 kernel weight. Further decomposition of simple correlation coefficients into direct and indirect effects showed that number of kernels per spike and 100 kernel weight had the largest direct effects on grain yield, under both stressed and non-stressed conditions' The expression of drought tolerance in the F1generation obtained from all possible combinations among genotypes differing in their responses to moisture deficit stress was studied. Analysis of variance revealed significantly high variability among genotypes for yield, yield components and drought tolerance measurements due to the effects of treatments. Drought tolerance was expressed in the crosses involving tolerant parents. The diallel analysis showed that mean squares for both GCA and SCA were significantly high at both moisture regimes. GCA:SCA ratios indicated predominance of additive gene action for all characteristics positively correlated with grain yield under stress or negatively correlated with drought susceptibility index. Differences in water use and transpiration efficiencies and interrelationships among water use and transpiration efficiencies and associated traits were investigated among durum wheat genotypes with differing responses to moisture stress. Significantly high genotypic variability in the amount of cumulative water used before (ETba) and after (ETpa) anthesis was observed. Susceptible genotypes used higher amounts of water before anthesis and lower amounts after anthesis. In contrast, tolerant genotypes used a higher proportion of water during the post-anthesis period. Significantly high variability among the genotypes was observed for various measures of water use and transpiration efficiencies, total dry matter and harvest index. Ranking of cultivars for water use efficiency based on grain yield (WUEG) and transpiration efficiency based on grain yield, was consistent with ranking of cultivars for drought susceptibility indices. Drought susceptibility index was significantly but negatively correlated with harvest index, WUEG and grain yield. However, it was positively and significantly correlated with the ETba:ETpa ratio. A high positive correlation of WUEG with harvest index and grain yield with harvest index was found. Differences in flag leaf water potential were significant only for genotypes under stress treatments. Water potential declined with age under both treatment conditions, however, the fall was faster in stress sensitive types than in tolerant types in more advanced growth stages. Inheritance of water use and transpiration efficiencies was studied in a hybrid population obtained from six parents, selected for their different responses to moisture stress. GCA and SCA effects were significant at both the moisture levels. The interactions of GCA and SCA with moisture levels were also highly significant. Analysis of the genetic components of variation demonstrated that WU E and T were under the control of additive and dominance type of genes. Narrow sense heritability estimates for water use and transpiration efficiencies based on grain yield (WUEG) were higher at the moisture stress level. Measures of water use and transpiration efficiencies showed significantly high and positive genotypic and phenotypic correlations among them as well as with grain yield and harvest index. The impact of the effect of moisture stress on growth and phenological development was examined among durum wheat genotypes differing in their tolerance to moisture stress. Drought stress was found to delay major growth stages and shorten the grain filling period. Drought tolerant genotypes had fast early growth, whereas susceptible ones had slow RGR initially. Variation in RGR was associated with NAR and LAR. Differences in hybrid performance were due to significant GCA and SCA effects. Interactions of GCA and SCA with moisture level were also highly significant. Moderate to high levels of broad sense heritability estimates were found for most of the traits. Significantly high genetic and phenotypic correlations between NAR and RGR, and LAR and RGR were found. The genetic and phenotypic correlations of grain yield with total dry matter, harvest index, RGR and LAR were significant. The effect of moisture stress on the content of water soluble carbohydrate (sucrose and D-glucose) was investigated in durum wheat (Triticum turgidum L. var. durum) above ground organs to assess and characterise the responses of genotypes with differing responses to drought stress. In all organs examined, drought tolerant genotypes accumulated more glucose and sucrose, particularly, at an early age. Stress caused an overall increase in the level of these carbohydrates, but the levels were highest in the stems compared to other organs. Level of drought (drought susceptibility index, 'S') was strongly related with the level of carbohydrates in the various plant organs Genetic differences among genotypes with differing responses to drought stress and their progenies obtained from all possible cross combinations were assessed using AFLP markers. Moderate to high level polymorph isms were obtained with the primer combinations evaluated. Euclidean genetic distance estimates showed that there was considerable genetic diversity among the materials studied. The correlation coefficient for pair wise genetic distance estimates based on AFLP data and yield, yield components, and morphophysiological traits was significant and positive. Cluster analysis showed that grouping of genotypes on the basis of AFLP data and agro-morphological data fairly agreed. A number of AFLP fragments were significantly correlated with the various traits evaluated under stress conditions. AFLP fragments were observed to affect a number of traits that were strongly correlated with drought susceptibility index.
Open Access
Analysis of genetic variability of grain mould resistance in grain sorghum
(University of the Free State, 2009-09) Mpofu, Leo Thokoza; McLaren, N. W.; Van Deventer, C. S.
English: In an effort to characterize the relationship between fungal pathogenicity and host genetic resistance, sorghum panicles of 11 genotypes were inoculated with five fungi frequently isolated from sorghum grain. Panicles were inoculated at anthesis with Fusarium graminearum, Fusarium thapsinum, Curvularia lunata, Phoma sorghina and Alternaria alternata spores. There were highly significant differences in the levels of fungal pathogenicity on different sorghum genotypes. These differences accounted for 58.4% of observed variation in ergosterol concentration. Genotype by pathogen (G x P) interactions accounted for 33.5% of the observed ergosterol concentration variation. The implication is that different genotypes reacted differently to different fungi. The genotypic reactions of the hosts accounted for 8.1% of the observed ergosterol concentration variation. Overall, fungal pathogenicity is the most important factor to consider in the evaluation of germplasm for grain mould resistance. Possible sources of resistance could be identified by use of biplot analysis of G x P interactions. Visual scoring for grain mould has limited value without identifying causal fungi. Fusarium thapsinum and Phoma sorghina were the most abundant fungi across all genotypes. Gene action and heritability for grain mould resistance in sorghum were investigated using a selection of 9 random pollen parents with varying levels of grain mould resistance to a different set of three random seed parents. Differences in ergosterol concentration were used as a measure of level of grain mould resistance among all genotypes. Use of ergosterol concentration as a measure of grain mould severity did not correlate with visual field scoring. Other traits measured include plant yield, plant height, kernel hardness, field grade score, days to flowering, glume color and seed color. The combined analysis of variance showed no genotypic variance for grain mould resistance. The expression of grain mould resistance was also not stable with significant genotype x location interaction. The analysis from Potchefstroom showed significant differences among genotypes whereas Cedara-1 and 2 showed no differences. Additive genetic variance was greater than dominance variance for all traits except grain mould resistance. A significant heterosis of -20.15% was observed for grain mould resistance indicating the importance of use of hybrid seed. LM124 (white seeded female) and LM130 (brown seeded female) produced resistant hybrids. Due to very high environmental variance, grain mould heritability could not be detected. Yield indicated the highest heritability of 0.41 at Cedara-1, plant height 0.39 at Cedara-2 and kernel hardness 0.38 at Potchefstroom. The significance of genotype by environment interaction was assessed over three environments. Differences in ergosterol concentration were used as a measure of level of grain mould resistance among all genotypes. Significant G x E interaction was detected after analysis of variance across all three locations. Single site analysis was then done to better explain the nature of the G x E interaction. Potchefstroom is the only location that showed significant genotypic responses to grain mould infection. Low grain mould pressure at Cedara-1 and Cedara-2 caused very low genotypic responses. A biplot was then used to indicate all genotypic performances across the three locations in a graphical design. Fungal species infecting sorghum kernels were isolated, counted and identified. Low genotypic responses at the Cedara locations seems to have been caused by prevalence of a less aggressive fungal species, Mucor spp. Weather variables did not correlate significantly with ergosterol concentration. Mycotoxin levels of aflatoxin, deoxyvalenol (DON), and zearalenone together with ergosterol concentration levels across 39 sorghum genotypes were measured. Varying levels of ergosterol and mycotoxins were observed across the three locations. There was no correlation between ergosterol concentration and any of the mycotoxins which indicates that mycotoxins concentration is not related to total fungal biomass. Mycotoxin concentration must therefore be related only to the biomass of the fungal species that is producing the mycotoxin among all fungal species infesting the grain. Farmers in Potchefstroom should be wary of aflatoxins and zearalenone while farmers in Cedara should choose varieties that tend to be low in DON and aflatoxins while not ignoring zearalenone.
Open Access
The analysis of the national wetlands vegetation database: freshwater lowland palustrine wetlands
(University of the Free State, 2015-12) Mtshali, Hlengiwe; Sieben, E. J. J.
The South African wetlands vegetation is not well known. Number studies were conducted to classify vegetation focusing mostly in small areas throughout the country. Data from all studies were collated and used to build the National Wetlands Vegetation database. This study was aimed at grouping the similar vegetation plots in the NWVD into plant communities, to find what extent environmental factors can explain patterns in plant species composition, to find which species can be used as environmental indicators in wetlands and to determine how the species respond to the environmental variables that drive the ecosystem. The database contains eight Main Clusters that are further subdivided into communities. Each of these Main Clusters is used as a starting point for further, more detailed analysis. Two of the Main Clusters, Sclerophyllous Wetlands Vegetation and Temperate Grassy Wetland vegetation w~re used for the purpose of the study. In order to understand the various types of wetlands and their environmental drivers, data analytical data analytical techniques were used to reveal patterns in species composition and their correlation with environmental factors. The multivariate methods used for the analysis of the database were cluster analysis, indicator species analysis, ordination, group testing, and species response curves. All of the above-mentioned methods make use of similarity measures among sample units. S0renson similarity measure was the measure of choice. Analysis was performed using the two data analytical I packages PC-Ord 6 and HyperNiche 2. The most contrasting influential environmental variables for South African wetlands are Soil texture, Hydrogeomorphic type and the Wetness index. This study also contributes to the management and conservation of water resources. Recommendations are made as to how the vegetation can be used in the assessment of wetlands health/quality and monitoring of wetlands, as well as management.
Open Access
Antimycobacterial activities of selected plants used in the management of tuberculosis in Sekhukhune (Limpopo Province), South Africa
(University of the Free State (Qwaqwa Campus), 2017) Madisha, Jacobus Kori; Ashafa, A. O. T.; Aiyegoro, A. O.
Tuberculosis (TB) continues to be a devastating disease of the world affecting more than two million people annually with one-third of the world’s populations suffering from the menace. The management of TB was in the use of orthodox medicines which are not only expensive but presents severe side effects. Thus, efforts are recently geared towards the use of alternative therapy from natural sources which could offer a lasting solution to the treatment of the diseases with little or no side effects. The study investigated the antimicrobial potentials of four medicinal plants used by Bapedi tribe of Sekhukhune area, Limpopo Province of South Africa. The antimycobaceterial efficacy of Aloe marlothii, Maerua angolensis, Drimia elata and Elephantina elephantorrhiza which were selected based on ethnobotanical study carried-out in the study was tested in four solvents such as ethanol, methanol, hydroethanol and dichlrormethane against four mycobacterium species such as M. tuberculosis, M. smegmatis, M. peregrinum, M. haemophilus and other gram positive and gram negative bacteria isolates using agar well dilution method and streak plate disc diffusion assay as a way of validating the anti-tuberculosis potentials of the plants. The results revealed the anti TB activity of the four plants particularly M. angolensis, D. elata and E. elephantorrhiza which were reported for the first time in this study. Similarly, the results revealed varied degrees of antimycobacterial activities of most of the screened extracts (particularly ethanolic and methanol) going by the zone of inhibition values (10 – 32 mm) as well as minimum inhibitory concentration (MIC) values that fell within the range of 0.098 - 1.56 μg/mL and as such, could be adjudged to possess anti TB potentials. Conclusively, the anti TB activity witnessed by the four plants could be attributed to the presence of the secondary metabolites which are responsible for the elicited effect. The study also validates the use of these plants in the management of tuberculosis by the Sekhukhune people of Limpopo Province, South Africa.
Open Access
Antioxidant activity and hepatoprotective potential of leaf extracts from Morella serrata (Lam.) Killick (Myricaceae).
(University of the Free State (Qwaqwa Campus), 2016-12) Mbhele, Nobuhle; Ashafa, Anofi O. T.; Abdelgadir, Hafiz A.; Ndhlala, Ashwell R.
Morella serrata L. Killick (Myricaceae) - is a South African plant finding therapeutic applications in oxidative stress related disorders including asthma, diabetes and male sexual dysfunction. The plant has not been scientifically investigated for its antioxidant and hepatoprotective activity. Thus the present study was aimed at determining the chemical constituents, antioxidant activity of M. serrata leaf extracts (ethanol, hydroalcohol and water) and hepatoprotective potential of aqueous-ethanol extract against carbon tetrachloride-induced liver injury in Wistar rats. Phytochemical screening coupled with quantification of phenolic compounds was performed in extracts using standard methods. The preliminary screening of M. serrata leaf extracts revealed the presence of flavonoids, tannins, phenols, saponins, steroids, terpenoids and resins whilst alkaloids, phlabotannins as well as cardiac glycosides were not detected. The total phenolic, flavonoid and flavonol content of the extracts ranged from 0.06± 0.01 to 0.24±0.02 mg GAE/g; 1.25± 0.01 to 2.04± 0.03 mg QE/g; and 0.35± 0.01 to 0.50± 0.01 mg QE/g respectively. The antioxidant activity of the extracts was assessed using DPPH, ABTS, nitric oxide, hydroxyl radical, reducing power, hydrogen peroxide and metal chelating assays using ascorbic acid as reference. Of all the tested extracts, the ethanol extract showed maximum free radical scavenging activity in the DPPH and nitric oxide scavenging activity assays while water extract showed maximum free radical scavenging activity in the ABTS, hydroxyl radical, hydrogen peroxide and metal chelating assay. Hydroalcohol extract showed maximum scavenging activity in the reducing power assay as compared to other extracts. A 21-day daily double dose protective effect of the graded doses (100, 200, 400 mg/kg body weight) of M. serrata hydro-alcohol extract was tested against CCl4-induced hepatotoxicity in Wistar rats using silymarin as a positive control. The effect of CCl4 was investigated on liver and body weight, feed and water intake, haematological parameters, serum biochemical functions, liver marker enzymes and liver histology. Findings revealed a significant increase in liver weight in CCl4-alone intoxicated rats compared to normal control. All groups intoxicated with CCl4 displayed a loss in appetite after CCl4 administration as compared to normal control. A decrease in body weight was observed in rats treated with CCl4-alone which was reversed following treatment with extract and silymarin. CCl4 intoxicated rats showed severe liver damage which was indicated by altered haematological parameters and elevated serum activity of ALP, ALT and AST. This was accompanied by a reduction in activity of marker enzyme CAT and a significant rise in TBARS concentration. This was however ameliorated in MSLAEE and silymarin treatments groups. Histopathological micrographs of hepatotoxic group revealed extensive liver damage characterised by severe necrosis, however, such damage was prevented in MSLAEE and silymarin pre-treated groups. The degree of damage in liver tissues was in the order CCl4- alone treated rats > 200 mg/kg b.w MSLAEE treated rats > 400 mg/kg b.w treated rats > 100 mg/kg b.w treated rats > Silyamrin treated rats > Normal control. Our findings from the research work provide support and evidence on the folkloric use Morella serrata as a potential natural antioxidant in treating oxidative stress induced ailments. The study also diverts from the perception that only the roots can be used to treat such ailments as the leaf extracts also showed effective antioxidant activity, thus contributing to the conservation of the plant. Data emanating from the further indicate that M. serrata was able to protect the liver against CCl4-induced oxidative damage in rats which may be attributed to its antioxidant and free radical scavenging activities.
Open Access
Antioxidant and antidiabetic potentials of Medicago laciniata (L) Mill root extracts: in vitro investigations
(University of the Free State (Qwaqwa Campus), 2017) Tshabalala, B. D.; Ashafa, A. O. T.; Balogun, F. O.; Sabiu, S.
Diabetes mellitus (DM) is one of the chronic ailments that contribute to high mortality rate worldwide. Synthetic drugs used to control and manage this disease have several constrictions like prohibitive price to the unemployed class and or low-income earners, disturbing side effects such as use during pregnancy. Due to these constraints and others, an alternative approach to control and manage DM is highly required. The aim of the current study was to investigate the in vitro antioxidant and antidiabetic potentials of Medicago laciniata (L) Mill root extracts. Solvents used for extraction of the plant material were hydro-ethanol, ethanol, water and acetone. Assays carried out in this investigation were phyto-chemical screening (qualitative and quantitative methods), antioxidant assays (DPPH radicals, reducing power, metal chelating, hydrogen peroxide, hydroxyl radicals and nitric oxide assays), and antidiabetic assays (alpha amylase and alpha glucosidase inhibition). Results showed that M. laciniata root possesses several medicinal phyto-chemicals like alkaloids, flavonoids, flavonols, saponins, tannins, cardiac glycosides and phenols. Quantification of phyto-chemicals showed 0.632 (μg/mL), 0.151(mg/g), 0.035 (mg/g) and 0.032 (mg/g) contents of total flavonoids, total flavonols, total phenols and total tannins respectively, while alkaloids and saponins showed 27 and 78% respectively. Antioxidant results revealed varied IC50 values of extracts in different assays performed. The lowest IC50 values recorded were 0.602±0.034 mg/mL, 0.712±0.072 mg/mL, 0.512±0.002 mg/mL, 0.306±0.021 mg/mL, 0.513±0.041 mg/mL and 0.455±0.164 mg/mL in DPPH radicals, reducing power, metal chelating, hydrogen peroxide, hydroxyl radicals and nitric oxide assay respectively. Hydro-ethanol extract showed the strongest alpha glucosidase inhibition with the lowest IC50 value of0.07±0.014 mg/mL while acarbose (standard) showed 0.24±0.17 mg/mL. All extracts showed poor alpha amylase inhibitory potential as compared to acarbose which was recorded to have the lowest IC50 value of 0.60±0.191 mg/mL. Among other extracts, ethanol extracts showed better alpha amylase inhibition with an IC50 value of 2.11±0.026mg/mL. Results obtained from different assays in this study suggest that Medigaco laciniata (L) Mill have antioxidant and antidiabetic potentials; may also possess other medicinal properties due to the variety of phyto-chemical discovered in this plant. Hence the study justified the folkloric use of this plant.
Open Access
Antioxidant, antidiabetic and cardioprotective activities of Dicoma anomala (sond.) used in the Basotho traditional medicine
(University of the Free State, 2016) Balogun, Fatai Oladunni; Ashafa, A. O. T.
𝑬𝒏𝒈𝒍𝒊𝒔𝒉 Dicoma anomala (Sond.) belongs to the Asteraceae family and locally called Hloenya (South Sotho), fever or stomach bush (Afrikaans). The plant is used in the management of various diseases, particularly diabetes mellitus among the Basotho tribe of eastern Free State Province, South Africa. The study evaluates the antioxidant, antidiabetic and cardioprotective potentials of the plant as a way of validating the folkloric usage. The result of in vitro antioxidant assays [2, 2- azino-bis (3-ethylbenzothiazoline-6-) sulfonic acid (ABTS), reducing power, superoxide anion, hydroxyl radicals, 1,1-diphenyl-2-picryl hydrazyl (DPPH) radicals, etc.] as well as phytochemicals (such as total phenol, total flavonoids and total antioxidant capacity) in various concentrations (1.56-25 µg/ml) tested using water, ethanol, hydro-ethanol and methanol extracts of the plant’s root revealed that the water extract exhibited the best activity with half maximal inhibitory concentration (IC50: 15.20, 11.70, and 0.84 µg/mL) in DPPH, hydroxyl radical, and superoxide anion radicals respectively. The four extracts also possessed high phenolic contents, total antioxidant capacity with lower total flavonoids content. The effect of treatment with 125, 250 and 250 mg/kg body weight (b.w.) aqueous roots extract of Dicoma anomala (AQRED) was investigated in vivo in CCl4- induced hepatotoxic rats in a 15-day curative and prophylactic study. The result revealed that pre-treatment and treatment with AQRED lowers the elevated serum activities of aspartate transaminase (AST), alanine aminotransferase (ALT) and the level of thiobarbituric acid reactive species (TBARS) while restoring the activities of liver antioxidant enzymes such as catalase (CAT), glutathione peroxidase (GPx) and superoxide dismutase (SOD) towards normal control in a dose-dependent manner. This result proved the antioxidant and hepatoprotective activity of the plant The in vitro antidiabetic potential of D. anomala was investigated via the inhibition of αamylase and α-glucosidase using same extracts (as above) at the range of 1.56 - 25.00 µg/mL concentrations. All the tested extracts of the plant were active against both enzymes, although, the most potent against α-amylase and α -glucosidase was hydro-ethanol (IC50: 9.00 µg/mL) and water (IC50: 27.41 µg/mL) respectively. Similarly, aqueous extract of the D. anomala displayed competitive and non-competitive inhibition of α -amylase and α - glucosidase respectively using Lineweaver-Burk plot. Treatment with AQRED at concentration 125, 250 and 500 mg/kg b.w. in Wistar rats reversed towards control the elevated blood glucose levels, lipid peroxidation, lipid profile, glycosylated haemoglobin and activities of gluconeogenesis enzymes, with concomitant reduction in the activities of enzymatic antioxidants, glycolytic enzymes as well as the high-density lipoprotein – cholesterol (HDL-c) brought about by streptozotocin induction. Thus, the study proved the antihyperglycaemic activity of the plant. Additionally, AQRED at 125, 250 and 500 mg/kg b.w. was evaluated for its ameliorative activity against isoproterenol (ISP) –induced cardiotoxicity in an animal model. The results from the evaluated biochemical parameters revealed significant (p< 0.05) in these parameters was observed. The data obtained indicate that the lethal dose (LD50) of AQRED is in excess of 2000 mg/kg and its oral administration for 90 days is unlikely to cause any toxic effects. In conclusion, the results from this study proved the antioxidant, antihyperglycaemic and cardioprotective potentials of AQRED. The results further validate the folkloric usage of the plant in the management of diabetes mellitus among the Basotho tribe of Eastern Free State Province, South Africa. ___________________________________________________________________
Open Access
The application of fossil grass-phytolith analysis in the reconstruction of cainozoic environments in the South African interior
(University of the Free State, 2009-05) Rossouw, Lloyd; Scott, L.
Grass-dominated ecosystems occupy a primary position with regard to current debates concerning key events in faunal turnover and human evolution in Africa. Our knowledge of how grass-dominated ecosystems in southern Africa have reacted to periods of global warming and cooling in the past is provided by a broad range of proxy data sources, most notably pollen and stable isotope records. Phytolith analyses provide an alternative fossil record of environmental change and are now progressively becoming a conventional analytical approach in palaeoenvironmental research.The grass family (Poaceae) produces abundant silica bodies, especially within specific and specialized silica cells located in costal zones of the leaf epidermis. In addition to being highly resistant to decomposition, grass phytoliths show markedly varied and distinct morphologies. In this study a central hypothesis, namely that the morphology of grass short-cell phytoliths consistently follows meaningful environmental traits that are rooted in the relationship between phytolith shape and the ecological niche of grasses, was investigated by interpreting morphologically diagnostic grass phytolith assemblages according to their association with the ecological requirements of the grass species that produces them, irrespective of taxonomic affiliation.An effort was therefore made to assign ecological meaning to short-cell phytoliths by comparing a range of ecological preferences in modern grasses with the phytoliths that they produce, rather than just using phytoliths to discriminate between grass subfamilies, tribes or genera. This entailed a systematic investigation of grass leaf epidermis from a collection of 309 species, followed by an assessment of the ecological significance of grass-short-cell phytoliths within a quantitative model. The model allowed for comparison of geographically diverse grass phytolith assemblages by converting them into one homogenous group represented by ecological categories. Several meaningful ecological trends were demonstrated by results in this study, and it is suggested that short cell phytolith association in grasses is primarily driven by a temperature gradient, marked by cool versus warm growing temperatures and reflected by grasses utilizing the C3 and C4 photosynthetic pathway. The study gives emphasis to the importance of investigating phytolith systematics with the aid of adequate comparative reference collections.
Open Access
Aspects of ß-1,3-glucanase expression in wheat associated with Russian wheat aphid resistance
(University of the Free State, 2003-11) Wilding, Willem Jacobus Marthinus; Van der Westhuizen, A. J.; Visser, B.
The aim of the study was to learn more about the expression of b-1,3-glucanase during the resistance response of wheat to the RWA (Diuraphis noxia)(Mordvilko). The different resistance genes (Dn1, Dn2 and Dn5) used in the study would shed more light on the possibility that b-1,3-glucanase expression is a universal biochemical resistance mechanism with regard to RWA. Tugela DN (Dn1) and Dn2 plants resulted in a similar expression pattern of b-1,3-glucanases after RWA infestation. The Dn1 and Dn2 cultivars had very high differential b-1,3-glucanase activity induction, which occurred much sooner compared to the infested susceptible plants. Wheat plants with the Dn5 resistance gene induced b-1,3-glucanase activity to a much lower level compared to the other two resistant lines. Northern blot analyses confirmed that the increase in b-1,3-glucanase activity and peptide levels in the Western blot analyses was due to increased transcription of b-1,3-glucanase genes. The induced b-1,3-glucanases were located intercellularly in the vascular bundle and mesophyll cell walls of wheat leaves. Intracellular the b-1,3-glucanases were primarily located in the chloroplast grana with low labelling found in the cytoplasm. Chloroplasts were isolated and fractionated to scrutinize results obtained with the localisation study. b-1,3-glucanase activity and Western blot analysis of chloroplast fractions verified these results with a 35 kDa b-1,3-glucanase residing in the chloroplast membrane bound fraction. These b-1,3-glucanases could play a role in the protection of the chloroplast of infested resistant plants.
Open Access
Assessing genetic diversity and identification of Microcystis aeruginosa strains through AFLP and peRRFLP analyses.
(University of the Free State, 2003-12) Oberholster, Paul Johan; Grobbelaar, J. U.; Botha-Oberholster, A. M.
English: There are 150 cyanobacterial genera and approximately 2 000 species known in the world. More than 40 of these have toxin producing strains. Cyanobacteria, commonly known as blue-green algae, are often present in small numbers together with a diverse assemblage of other photosynthetic algae that naturally occur in surface water worldwide. However, under conditions of warm temperatures, minimal water movement and elevated concentrations of phosphorus in a water body, cyanobacteria may frequently become dominant and form thick scums of floating algal cells. These dense aggregations of floating cells, termed 'blooms', presents a number of water quality problems; most often offensive odours and tastes, and sometimes biotoxins that can be divided into alkaloid neurotoxins and cyclic peptide hepatotoxins, commonly from the genus Microcystis and released in waterbodies. The neurotoxins act chiefly at neuromuscular junctions and cause rapid death because of respiratory paralysis. The hepatotoxins act on the hepatocyte cytoskeleton and cause intrahepatic haemorrhage and centrilobular necrosis. Clinically the hepatotoxin most often causes peracute or acute death, or subacute poisoning with signs such as icterus and hepatogenous photosensitivity. Currently cyanobacterial taxonomy does not provide an unequivocal system for the identification of toxigenic and bloom-forming genus Microcystis. The ambiguities that exist in the cyanobacterial taxonomy are due to the expressed variability, minor morphological and developmental characteristics that are used for identification. In this study geographically unrelated axenic strains of Microcystis aeruginosa were obtained from the Pasteur Institute, France (PCC); the National Institute for Environmental Studies, Japan (NIES); the Institute of Freshwater Ecology, UK (CCAP); the Pflanzen Physiologisches Institut, Universitat Gottingen, Germany (SAG) and the University of the Free State, South Africa (UV) culture collections. Nonaxenic strains were collected from Hartbeespoort, Rietvlei and Roodeplaat Dams in South Africa. After screening 20 primer combinations on a subset of strains eight IRDye700™-labeled EcoR1 primer pairs were selected for amplified fragment length polymorphism (AFLP) analysis to determine the genetic relationship of these geographically unrelated strains. A total of 909 bands were amplified from the eight primer combinations, of which 665 were informative, 207 non-informative and 37 monomorphic, with an average of 83.12 polymorphic bands per primer combination. The genetic relationship among all the Microcystis aeruginosa strains based on the combination of data obtained with the eight primer combinations was analysed employing the Unweighted Pair Group Method using Arithmetic Means (UPGMA) algorithm and presented as a dendrogram. In the dendrogram, the strains from Rietvlei (UP01) and Hartbeespoort Dams (UP04) grouped together and were thus genetically closer to each other, than to the strain from the Rhoodeplaat Dam (UP03). The Japanese strains (NIES88, NIES89, NIES90, NIES99, NIES299) also grouped separate from the other strains, with NIES90 and NIES299, genetically closest to each other. Interestingly, Microcystis aeruginosa strain PC7806 that originated from The Netherlands, also grouped within this group. Microcystis aeruginosa strains CCAP1450/1 (UK), UV027 (South Africa) and PC7813 grouped together, and are genetically closer to the UP-strains, than any of the other strains. In the present study, AFLP analysis proved useful for the identification of genetic diversity and analysis of population structure within Microcystis aeruginosa. In order to link the identification of strains with toxicity, the utility of the mcyB gene sequence for identification of strains was tested. Based on conserved motifs present in known sequences of mcyB four primer pairs were designed. Using the primer pairs Tax 3P/2M, Tax 1P/1M, Tax 7P/3M and Tax 10P/4M, the mcyB gene from PCC7813 and UV027 were sequenced, resulting in fragments of 2174 and 2170 base pairs in size, respectively. The obtained sequences were analyzed using nucleotide BLASTN annotation of the Basic Local Alignment Search Tool (BLAST). The sequence alignment indicated high homology to other published sequences in GenBank (AY034601 for pee7813 and AY034602 for UV027; e-value = 0.0). Upon further analysis of the sequences it was obvious that there are several base differences between the sequences of the two strains, which led us to investigate the potential of using differences in restriction sites, and thus insertions/deletions (indels) in nucleotide sequence to discriminate between the other M. aeruginosa strains, as well as using the mcyB gene to discern between M. aeruginosa and M. wesenbergii in raw water samples. A vast number of restriction sites were identified with differences followed by restriction digest of the specific polymerase chain reaction (PCR) mcyB gene fragment. This work demonstrates that PCR assays provide a useful indicator of toxicity as well as the identification of taxonomical characteristics between laboratory cultures and environmental isolates. A number of questions arise from the present study and future research therefore needs to address the following issues: • Are there more than one Microeystis aeruginosa strain / "population" present at a given time in a specific water reservoir? Do these populations change through the season? What role does the individual populations play in a cyanobacterial bloom? Thus, the dynamics and structure of populations need to be clarified. • Which mcy gene in the cluster is mostly responsible for toxin production? Does the expression of the genes correlate with gene structure/sequence? What role does the environment play in determining the level of expression, and thus toxin production?
Open Access
Assessment and genetic improvement of aluminium tolerance in South African winter bread wheat cultivars
(University of the Free State, 2010-05) Motupa, Mamotlole Patricia; Labuschagne, M. T.; Malan, A. F.
English: This study was undertaken to evaluate 11 wheat genotypes for aluminium tolerance using three laboratory based evaluation methods. Four parameters namely the root length before aluminium treatment, the root re-growth after aluminium treatment, the portion of the root affected by aluminium treatment, stained with hematoxylin and root tolerance index were measured on the two longest (primary and secondary) roots of each seedling to determine the effect of aluminium toxicity on the physiological development of the seedling roots. With the root re-growth method it was possible to distinguish between three categories of tolerance (moderate, intermediate and tolerant) that will be very helpful in future resistance breeding for aluminium tolerance. With this method it is possible to discriminate between individuals in a population for aluminium tolerance. Similar data was obtained for the primary and secondary roots, which indicated that the age of the roots are not a limiting factor for aluminium tolerance screening with the nutrient bioassay. Although the root re-growth method discriminated between the different aluminium tolerance categories, a better indication of aluminium tolerance categories was achieved with the root tolerance index method. With the above methodology in place it was possible to observe an increase in aluminium tolerance in some progeny after gene recombination and it was possible to discriminate between good aluminium tolerant progeny and progeny showing no genetic gain from the hybridisation. It was also shown that there were no reciprocal effects for aluminium tolerance in wheat. There were genetic differences for aluminium tolerance between the genotypes used in this study and this methodology can be successfully implemented in an aluminium tolerance-breeding programme for wheat. This study indicated that there is useful methodology to effectively follow the genetic gains during gene-recombination for aluminium tolerance and, secondly that there are different genetic resources available in wheat that can be utilised to increase aluminium tolerance.
Open Access
Assessment of adult plant resistance to stripe rust in wheat
(University of the Free State, 2004-05) Pienaar, Lizaan; Pretorius, Z. A.
English: The objective of this study was to develop and optimise methods to detect adult-plant resistance (APR) in wheat to stripe rust caused by Puccinia striiformis f.sp. tritici. A collection of spring wheats was tested at the seedling stage with different temperature and light regimes to test the hypothesis that environmental variation can induce APR expression in primary leaves. Treatments included pre-inoculation conditioning of seedlings at either 18° or 25°C, followed by post-inoculation temperature and light treatments. In some treatments intermittent low and high temperatures (18° or 25°C) were used as well as a treatment with continuous low temperature (10°C). The highest infection types were encountered with a pre-inoculation treatment of 18°C combined with a 24 h light cycle, and a post-inoculation treatment of 18°C combined with a 18 h light and 6h darkness cycle. Day length influenced infection types more than temperature. All treatments subjected to less than 14 h light per day showed a reduction in infection levels. Dark periods experienced prior to inoculation were not conducive to infection type development. Clear banding of infection zones and reduced sporulation occurred. Based on the lack of correlation between seedling infection types and adult responses observed in the field, no environment was conducive to expression of APR to stripe rust in seedlings. Rating of adult plants for stripe rust resistance has traditionally been problematic in terms of infection levels and repeatability. Furthermore, several attempts to investigate the reaction of normally grown adult plants in the glasshouse failed due to leaf damage. To improve these methods, an accelerated system of producing adult wheat plants in a controlled environment was tested. By manipulating plant density, pot size, light and temperature, wheat plants reached maturity quicker than normally grown adult plants and were referred to as mini-adult plants. In terms of leaf damage the mini-adults were better suited for flag (terminal) leaf evaluation. For optimum results, the mini-adult plants should be grown in a glasshouse rather than growth chamber and inoculated between heading and flowering. According to flag leaf infection type and whole plant reactions observed, the mini-adults provided an acceptable system for comparing adult plants to different isolates of P. striiformis. This system accurately detected APR in most winter wheats tested and was reliable for a collection of CIMMYT spring type wheats. Disease ratings of 98 CIMMYT lines tested with this accelerated system showed a correlation of 88% with field ratings. The mini-adult plant system was also tested with populations segregating for APR. Because of the likely application of genetic studies to resistance breeding, it is essential to correlate glasshouse tests with field assessments. The approach followed in the present study conformed to guidelines in terms of selecting cultivars with high levels of APR not previously analysed, as well as comparing glasshouse and field data. Segregation ratios indicated the presence of two resistance genes in the F3 of a Baviaans x Avocet S cross (χ²7:8:1 = 0.1029), but were inconclusive for a Sunmist x Avocet S cross where Mendelian ratios could not be confirmed. The accelerated screening system was less successful than the screening of pure lines. Based on the fact that the reaction of Avocet S was not completely susceptible in the glasshouse, and most likely influenced ratios, the lower success rate appeared to be a function of the parental genotypes rather than in the system in general. Compared to the normal glasshouse procedure, the improved APR system took significantly less time and physical resources to achieve ratings.
Open Access
Assessment of cup quality, morphological, biochemical and molecular diversity of Coffea arabica L. genotypes of Ethiopia
(University of the Free State, 2005-09) Bekele, Yigzaw Dessalegn; Labuschagne, M. T.; Herselman, L.; Osthoff, G.
The genetic diversity of C. arabica genotypes collected from the northwestern and southwestern parts of Ethiopia was evaluated using morphological, biochemical and molecular (AFLP and SSR) markers. The objectives of the study were to (1) estimate the level of genetic variation among currently grown C. arabica genotypes, (2) estimate the level of associations among agro-morphological characters, coffee quality traits and green bean biochemical compounds, (3) compare the level of genetic variation between coffee genotypes collected from the northwestern and southwestern parts of Ethiopia and (4) compare the efficiency of AFLP and SSR markers in detecting genetic variation in C. arabica. Results of diversity analysis using nine qualitative and 18 quantitative morphological characters indicated the presence of substantial variability among evaluated coffee genotypes. Genotypes were significantly different for all 18 quantitative morphological characters. Higher Shannon-Weaver diversity indices ranging from 0.401 to 0.989 were recorded for nine qualitative morphological characters. Cluster analysis using qualitative, quantitative and a combination of qualitative and quantitative characters classified genotypes into two groups. Qualitative characters failed to independently distinguish seven of the genotypes. Principal component analysis grouped 18 quantitative characters into 15 principal components and the first four explained 82.3% of the entire variability among genotypes. Average green bean yield per tree and bean length were important for the variation explained in three of the first four principal components. Correlation analysis performed among 18 agro-morphological characters indicated positive associations between average green bean yield per tree and all other characters. Average green bean yield per tree had statistically significant correlations with percentage of bearing primary branches per tree, bean weight, canopy and trunk diameters, tree height, bean length and thickness, internode lengths of orthotropic and primary branches and fruit and petiole lengths. Broad sense heritability varied from 38% for bean thickness to 94% for bean weight and number of secondary branches per tree. Average green bean yield per tree, canopy diameter, tree height and bean weight had higher genetic coefficients of variation and broad sense heritabilities. These characters were positively and significantly correlated, allowing simultaneous improvement of these traits. Genotypes were evaluated for variability in four cup quality traits (acidity, body, flavour and overall standard) and four green bean physical characters (bean shape, size, uniformity and weight). Considerable variation was observed among genotypes both for cup quality as well as green bean physical characters. Of all the genotypes, AD0691 and AD1691 had both desirable cup quality and green bean physical characters. Cluster analysis performed using cup quality and green bean physical characters, classified genotypes into two groups. Genotypes were not clustered according to collection regions. All cup quality traits were positively and significantly correlated and correlation coefficients ranged from 0.69 to 0.93. Positive correlations were observed among desirable cup quality and green bean physical characters indicating that cup quality and green bean physical characters can be improved simultaneously. Genotypes were evaluated for green bean caffeine, chlorogenic acids, sucrose and trigonelline content variability. Analysis of variance indicated significant differences among genotypes for all biochemical compounds. Green bean caffeine, chlorogenic acids, sucrose and trigonelline contents ranged between 0.91-1.32%, 2.34-4.67%, 5.30-8.98% and 1.04-1.71%, respectively on dry matter basis. Cluster analysis classified coffee genotypes into eight groups and genotypes were not clustered according to collection regions. Coffee genotypes collected from northwestern Ethiopia were more diverse in green bean caffeine, chlorogenic acids and sucrose contents compared to southwestern Ethiopia genotypes. On average, southwestern Ethiopia coffee genotypes had higher green bean caffeine, chlorogenic acids, sucrose and trigonelline contents compared to northwestern Ethiopia genotypes. Green bean caffeine content showed negative and statistically significant associations with all desirable cup quality attributes and correlation coefficients ranged from -0.305 to -0.407. Desirable cup quality traits and low green bean caffeine content can be selected simultaneously. Green bean sucrose content showed positive associations with all desirable cup quality and green bean physical characters. Higher green bean sucrose content, desirable cup quality as well as green bean physical characters can be improved together. The genetic diversity of coffee genotypes was investigated using 10 AFLP primer combinations. Results revealed differences among AFLP primer combinations in detecting genetic variation among genotypes. Of the 10 primer combinations EcoRI-ACA/MseI-CAA, EcoRI-ACC/MseI-CAG, EcoRI-ACT/MseI-CAG and EcoRI-AAC/ MseI-CAA were superior in detecting genetic variation. Almost all primer combinations were positively correlated in estimating pair-wise genetic similarity coefficients, indicating the similarity of primer combinations in detecting genetic variation among genotypes. All genotypes were independently distinguished and pair-wise genetic similarity coefficients ranged from 0.851 to 0.982 with an average of 0.915. Ten genotypes had 18 specific AFLP markers which could be utilised for genotype fingerprinting. AD1291 and AD1491 were the most dissimilar while AD3591 and AD3991 were the most similar genotypes. Genotypes were classified into two groups using UPGMA method of cluster analysis. Genotypes did not cluster according to collection regions. Results unveiled the presence of genetic variation among genotypes collected in each region and the presence of close genetic similarity among some coffee genotypes collected from different regions. The genetic diversity among coffee genotypes from southwestern Ethiopia was higher compared to those from northwestern Ethiopia. Genetic diversity analysis performed using six SSR primer pairs indicated the presence of considerable genetic variation among some of the genotypes collected from northwestern and southwestern Ethiopia. Twenty polymorphic SSR markers were amplified of which two were specific to genotypes AD1491 and AD2991. Using 20 polymorphic SSR markers, 64.3% of the genotypes were independently distinguished. Pair-wise genetic distances ranged from 0.286 to 1.000. The lowest pair-wise genetic similarity coefficient was recorded between AD0591 and AD1491 as well as AD1491 and AD4591. Genotypes from southwestern Ethiopia were more diverse compared to those from northwestern Ethiopia. Molecular markers differ in the amount of information generated per PCR reaction. The efficiency of 10 AFLP primer combinations and six SSR primer pairs in detecting genetic variation was compared using 28 C. arabica genotypes. AFLP primer combinations amplified 220 and SSR primer pairs 20 polymorphic alleles among evaluated genotypes. AFLP markers independently distinguished all evaluated coffee genotypes whereas SSR markers distinguished 64.3% of the genotypes. Moreover, 18 genotype specific AFLP markers compared to two SSR genotype specific markers were identified. The assay efficiency index of AFLP markers (22) was far superior to that of SSR markers (3.3). AFLP markers surpassed SSR markers in detecting genetic variation among evaluated arabica coffee genotypes. Results of this study indicated the presence of good congruence between the two genetic markers in estimating pair-wise genetic similarity coefficients among genotypes.
Open Access
An assessment of endophytic fungi in needles of three pinus spp. cultivated in South Africa
(University of the Free State, 1999-11) Kriel, Wilma-Marie; Swart, Wijnand J.; Crous, Pedro W.
English: Endophytes, in the strict sense, are organisms that cause symptom less infections in plants. As symptomless mutualists, they can act as biocontrol agents of herbivorous insects and plant diseases. They can also be indicative of host vitality and environmental pollution. Some endophytes, however, are latent pathogens with an endophytic phase. Pine needles are colonised by various species of endophytic fungi. It is well-known that the endophytic biota vary with host species, as well as with time. Therefore the aim of this study was to qualitatively and quantitatively compare endophyte populations within the canopies of Pinas patula, P. radiata and P. elliottii, during winter and summer, and within the canopies of two separate P. radiata trees, over different seasons. Endophytic fungi were isolated from pine needles, sampled in different seasons from various positions within the canopy, by plating surface-sterilised needle sections onto cornmeal agar supplemented with antibiotics. In the first study a significant difference (P < 0.05) in endophyte numbers between samples collected during winter and summer was observed. Pinus patula and P. elliottii were more intensively colonised during winter than summer. In P. radiata, however, the number of fungi isolated in summer was significantly higher than in winter, but the fungal species isolated were consistent. Cydsneusms minus and a sterile white yeast-like fungus were most commonly isolated. Cyclsneusms minus is a latent pathogen causing autumn needle cast, and sterile yeast-like fungus is suspected to be a true endophyte. Similar endophytic fungal species were isolated in the second study, performed on two eight-year-old P. radiata trees. Samples were taken during four seasons from an isolated, solitary tree and one growing in an even-aged, plantation nearby. Five needle fascicles of four different age groups were collected from each tree. One needle per fascicle, including the fascicle sheath, was cut into 12 sections and used for the isolations. In general, fewer endophytes were isolated from the solitary tree than the plantation tree. Qualitative and quantitative differences in endophyte populations were observed within needles as well as between needle age groups and seasons. The aim of the third study was to conduct a qualitative assay of enzyme production of 2 t predominant fungal endophytes isolated from the pine needles. The enzymes assayed included cellulase, pectinase, lipase, laccase, phenol oxidase, protease, B-glucosidase, cytochrome oxidase, and peroxidase. Results were consistent with attributes associated with leaf penetration and longterm residence of fungi within pine needles. All fungi screened produced at least two of the enzymes assayed. Different substrate utilisation patterns suggest biochemical partitioning of nutritional resources by endophytes. The ubiquitous presence of lipolytic activity in all isolates tested, suggests the ability to lyse cuticular waxes in order for penetration to occur. The tolerance of most tested fungi to tannic acid (phenol oxydase production) suggests low sensitivity to phenolic compounds (tannins etc.) normally present in pine needle tissue. Management practices in plantations that reduce or increase the environmental stress on individual trees, thereby influencing endophytic populations, could have distinct beneficial or negative effects on the general vitality of trees. The most important effects of certain practices would be the influence they have on latent pathogens such as C minus. Further investigation of foliar endophytic fungi of intensively managed pine plantations is therefore justified with a view to understand the effects management practices have on their ecology.
Open Access
Assessment of genetic diversity, combining ability, stability and farmer preference of cassava germplasm in Ghana
(University of the Free State, 2012-11-11) Parkes, Elizabeth Yaa; Labuschagne, Maryke T.; Fregene, Martin A.
English: The aim of this study was to assess genetic diversity, combining ability, heterosis, heritability of traits, stability and farmer preference of cassava germplasm in Ghana in order to structure an effective breeding programme. The assessment of genetic diversity in a collection of local cassava genotypes using 33 SSR markers revealed a high overall heterozygosity. The SSR markers identified 63 duplicates in the collection. The heterotic pools were distinct for the savannah and the forest ecological zones and this was the basis for the selection of progenitors for the rest of the study. Seven and five cassava progenitors were crossed in a diallel design without reciprocals in the forest and savannah ecologies respectively. The progenitors and progenies were evaluated for CMD, CBB, yield and its components in two seasons in the forest and one season in the savannah zone. The GCA:SCA ratio indicated that the GCA was larger than SCA for average root number, indicating additive gene effects and a possibility for improvement by selection. SCA was larger than GCA for harvest index and fresh root yield, indicating environmental effects on the trait and confirms the non-additive effects mainly determining expression of root yield. The parental genotypes were selected from a particular region where CMD is the main economic constraint. Debor had the best GCA effect for cassava mosaic severity reaction; while Tuaka had the best GCA effect for fresh root weight. Debor x Kwasea was the best combination for CMD resistance. Debor and Kwasea were the best parents for resistance breeding to CMD. The predictability ratio varied between 0.58 and 0.84. CMD and root number had a ratio close to one for the savannah and forest zones, showing that these traits were highly heritable and influenced by additive gene action. Marker assisted selection was used to search for new sources of CMD resistance in the progenies and progenitors. Crosses among CIAT elite genotypes and landraces revealed progenitor Dabodabo as a putative source of new genes to CMD resistance.