Masters Degrees (Plant Sciences)

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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
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
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
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
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 South African bread wheat cultivars for milling quality
(University of the Free State, 2003) Aucamp, J. C.; Van Deventer, C. S.; Labuschagne, M. T.
English: The objectives of this research were to assess South African winter and facultative bread wheat cultivars for milling quality, to study the effect of genotype x environment interaction on the stability of the wheat quality and to characterise the cultivars for milling performance. Thirteen hard red varieties were planted at six localities throughout the Free Sate at two planting dates, during 1997 to 1999. Betta-DN, Gariep, Molen, SST 367, SST 966 and Tugela-DN were planted at the first planting date. Betta-DN, Caledon, Elands, Gariep, Limpopo, PAN 3235, PAN 3349, SST 124, SST 972 and Tugela-DN were planted at the second date. Material was evaluated for test weight, thousand kernel weight, kernel diameter, kernel hardness, moisture content, vitreous kernels, break flour yield, flour yield, flour colour and flour protein content. Combined ANOVA's for the characteristics was performed over environments. Cultivar differences were determined by means of the least significant difference at individual localities. The analysis indicated highly significant differences among genotypes, environments and GXE interactions, for most of the measured traits. Genotypes contributed significantly to the variance in BFLY, DIAM, TKW and Hl. Environment had a large effect on TW, MOIST, VK, FLY, FCL and FPC. Significant GXE interactions were present for most of the quality traits. Canonical variate analysis was used to differentiate between cultivar groups and indicated that TKW, DIAM, HI, BFLY and TW could effectively differentiate between cultivars. The groups observed with regard to the mentioned characteristics were Gariep with Betta-DN and Molen with SST 966. Tugela-DN and SST 367 were not similar to any other cultivars. At the second planting date, Tugela-DN grouped with SST 124. Betta-DN, Caledon, Elands, Gariep, Limpopo and PAN 3235 formed a group. SST 972 and PAN 3349 were not similar to each other or to the other cultivars. The correlation matrix was performed, to calculate phenotypic relationships between quality traits. TKW had positive correlations with DIAM and these two characteristics indicated positive correlations with MOIST. HI correlated positively to TW and also correlated positively to VK. HI and VK correlated negatively to BFLY. High negative correlations were found between HI and FLY. FLY had positive correlations with BFLY, but correlated negatively with FLC. Stepwise multiple regressions indicated that only small percentages of the variation in TW, HI, BFLY, FLY and FLC could be explained by the other kernel and milling characteristics. HI explained the variation in the TW the most effectively. VK and MOIST could be regarded as the most important variance predictors for HI. Predictors for BFLY were kernel size and HI. These characteristics could define 41.6 to 63.3% of the variation in BFLY. Kernel hardness measurements, HI, BFLY and VK were the most definable for flour yield, together they interpreted up to 50.0% of the variation in FLY. TW explained less than 4% of the variation in FLY; therefore TW is not always reliable in predicting flour extraction. The kernel size explained less than 9.6 to 20.7% of the variation in FLY, illustrating the difficulty of predicting flour yield by indirect calculations. The most important variable in predicting FCL was FLY. AMMI analysis of variance was performed to investigate the influence of the GXE interaction on milling quality. Every locality by year combination was treated as a separate environment. Analysis confirmed differences in genotype performance, that there were varying growth conditions among the localities and the presence of GXE interactions. Interaction effects on TW, percentage VK, FLY, FCL and FPC, were large. IPCA 1 stability scores were compared to the AMMI stability values. Molen was the most stable cultivar at the first planting date. At the second planting date, PAN 3235 and Limpopo were the stable cultivars. Betta-DN, SST 124 and Caledon were also quite stable. Tugela-DN, PAN 3349, as well as the hybrid cultivars SST 966 and SST 972, were unstable with regard to milling quality. Milling performance, as calculated by flour extraction, ash contents and flour colour in various formulas, revealed Gariep and Betta-DN as the high performing cultivars (first planting date), while Molen and Tugela-DN reflected poorer performances. The most effective performing cultivars at the second planting dates were SST 124, PAN 3235, Betta-DN and Limpopo. PAN 3349, SST 972 and Tugela-DN indicated poorer milling performances.
Open Access
Bioactivity of traditional medicinal plants used in the treatment of tuberculosis in the Free State, South Africa
(University of the Free State (Qwaqwa Campus), 2016-06) Hlongwane, Mandla Victor; Komoreng, L. V.
Many medicinal plant species were once used as a primary source of all medicines in the world and they continue to provide humankind with new remedies. Tuberculosis (TB) is one of the dreaded diseases that have been managed using medicinal plants. TB continues to be one of the airborne diseases that cause more deaths in the world than any other infectious diseases. The TB bacteria (Mycobacterium tuberculosis) has become resistant to the orthodox drugs used to treat TB diseases. Most strains of TB which have become resistant to all major anti-TB drugs have emerged. In the present study, eight medicinal plant species (Dicoma anomala, Xysmolobium undulatum, Hermania depressa, Lotinonius lanceolata, Senecio harveianus, Lentsweni, Eucomis automnalis and Drimia depressa) that are traditionally used in the Free State province for the treatment of respiratory infections were collected for investigation. An ethnobotanical survey was conducted from January to June 2014 in consultation with the traditional healers and herbalists of the Free State Province. Plants were collected, extratced and tested for phytochemicals, antibacterial, antifungal and antimycobacterial activity. The phytochemical carried out revealed some of the secondary metabolites being absent in some of the plants and present in others. X. undulatum and E. automnalis revealed the presence of saponins only. Lentsweni and H. depressa revealed the presence of tannins, saponins and terpenoids, whereas L. lanceolata and S. harveianus revealed the presence of tannins, saponins, flavonoids and cardiac glycoside.Antibacterial activity was tested using four bacterial strains; two Gram-positive strains (Bacillus pumilus and Staphylococcus aureus) and two Gram-negative strains (Klebsiella pneumoniaeand Escherichia coli), while the antifungal activity was tested against two fungal species namely Candida albicans and Trichophyton mucoides. The test for antimycobacterial activity was done against the causative agent of tuberculosis (M. tuberculosis). Extracts exhibiting low or no antibacterial activity were D. anomala (methanol and aqueous extracts), X. undulatum (acetone and aqueous extracts), Lentsweni (methanol extract), E. automnalis (ethanol and methanol extracts). Good antibacterial activity was observed with the acetone and ethanolic extracts of D. anomala having the highest activity against K. pneumonia (0.130 mg/ml) and E. coli (0.781 mg/ml), with B. pumilis and S. aureus having the best antibacterial activity (MIC value of 0.098 mg/ml). Promising results were detected with the ethanolic extracts prepared from X. undulatum, L. eriantha and D. depressa against all the bacterial strains with MIC values of 1.563 mg/ml. The antifungal activity of the acetone, ethanol, methanol and aqueous extracts prepared from the eight selected medicinal plant species displayed the best activities against C. albicans and T. mucoides, with sMIC values ranging between 0.098 to 0.781 mg/ml. The best antimycobacterial activity was detected with all lipophilic extracts prepared from S. harveianus with MIC values of 0.195 mg/ml. H. depressa organic solvents extracts exhibited good activity against M. tuberculosis with MIC values of 0.78 mg/ml. The selected medicinal plants used for the treatment of respiratory ailments in the Free State Province have demonstrated significant activities, which may better explain and justify their frequent use by the traditional healers. These results might give some leads for further analysis in order to develop new pharmaceutical drugs derived from plants.
Open Access
Biochemical and molecular analysis of the early response of Triticum aestivum infected with Puccinia striiformis f.sp. tritici
(University of the Free State, 2005) Van Zyl, P. J. L.; Visser, B.; Van der Westhuizen, A. J.
English: The aim of this study was to establish the oxidative burst and the involvement of protein kinases in the early responses involved in the resistance of a resistant wheat cultivar (Yr1) to Puccinia striiformis f. sp. tritici, thereby establishing the earliest point of recognition and the onset of defense responses to the intruding pathogen by the plant. This time period was then used in an attempt to clone genes involved in the downstream signaling. protein from Oryza sativa and a HGWP repeat containing protein from Oryza sativa respectively. Although no unique motifs were present on the respective polypeptide sequences, the presence of various phosphorylation sites indicate possible regulation through phosphorylation. An XYPPX repeat was present on the polypeptide sequence of 05WVZ03, while an N-glycosylation and an N-myristoylation was present on 05WVZ05 and 05WVZ06 respectively. The isolated cDNA fragments were present as single copy genes in various resistant cultivars, as well as in the susceptible cultivar, Avoset-S, indicating that these genes are not unique to any one resistance cultivar. While naturally expressed in the IR plants, three genes (05WVZ01, 05WVZ05 and 05WVZ06) showed induced expression in the IS plants. The fourth gene (05WVZ03) was apparently expressed as multiple copies within wheat. The expression profiles of none of the clones however indicated a real involvement in signaling. Plants are continuously challenged by a variety of pathogens. To survive these challenges, plants possess an arsenal of defenses, which are activated upon the recognition of the pathogen through certain signaling events. In some cases the difference between resistance and susceptibility lies in the timely activation of signaling. Early signaling events include protein phosphorylation and dephosphorylation and the production of reactive oxygen species (ROS). To establish the earliest time of recognition and the activation of defense responses, the occurrence of the oxidative burst in the plant was first established, whereafter the activation of protein kinases were determined. The oxidative burst was assessed through various enzyme activities e.g. NADPH oxidase, superoxide dismutase (SOD) and peroxidase (POX) activity as well as H2O2 levels. The earliest response of the plants was 18 h.p.i. when total protein kinase activity almost doubled in the infected resistant plants. This was followed by a similar increase in activity 48 h.p.i. Both increases in total protein kinase activity were accompanied by increases in H2O2 levels and glutathione peroxidase activity. However, the second increase at 48 h.p.i. was more significant and is therefore concluded to be the oxidative burst. The recognition of the pathogen, as well as the activation of the defenses therefore occurred between 18 and 48 h.p.i. Once this reaction time was established, differentially expressed cDNA fragments were amplified using DDRT-PCR. Eight different gene fragments were isolated, cloned and sequenced. These isolated cDNA fragments showed different levels of homology to four known polypeptides namely, a Nodulation protein B (fragment) from Rhizobuim sp, a TOBAC Hypothetical protein from Nicotiana tabacum, a Hypothetical
Open Access
Biological control of bacteria wilt in tobacco caused by Ralstonia solanacearum
(University of the Free State, 2007) Terblanche, Johanna Dina; Swart, W. J.
The phase out of well-known chemical control products, especially soil fumigants, is a reality and biological control strategies need to be explored. Biological control rarely eliminates a pathogen from the soil, usually it reduces its numbers or ability to induce disease. However combining complementary biological control tactics may become the only tool in integrated control management for soilborne diseases. The biggest challenge will be to determine the most feasible sequence of techniques for optimal control of each pathogen, farming system and geographic area. Other factors that may have an influence on the efficacy of any bio-control strategy are host related (genetic resistance), environment related (longevity. soil type & climate) and pathogen related (virulence, inoculum density, survival). There is considerable interest in biofumigation as an alternative to synthetic soil fumigants in horticulture and agriculture. The term biofumigation usually referrers to the biocidal effects of isothiocyanates (ITC’s) released from Brassicaceous plants. It can and should however be extended to other volatile bio-substances with the same qualities like thiophene, a heterocyclic, sulphurous compound released by Tagetes spp. The rhizosphere presents a complex integrated ecosystem. Biotic and abiotic factors present, can determine the dynamics and structure of the microbial population in a specific rhizosphere. Screening different crops for rhizosphere suppression of soilborne pathogens can be a point of departure to select crops for a specific crop rotation system. A series of summer- and winter crops were evaluated for rhizosphere suppression of Ralstonia solanacearum (Race 1, Biovar III), causal agent of bacterial wilt in tobacco. Ocimum basilicum (sweet basil), Tagetes erecta (giant marigold), T. patula (dwarf marigolds), Coriandrum sativum L. (coriander) and Triticum aestivum L. (wheat cv. Inia) resulted in a significant control of the pathogen. However all Tagetes spp.had the lowest pathogen population count of all crops evaluated. A greenhouse trial conducted in 0,5 m deep soil indicated that the T. patula in combination with non-host winter crops, could reduce the pathogen population of the soil to such an extent that the disease incidence on the followup tobacco crop was 40% lower than that of the initial tobacco crop. A four-year rotation trial on a heavily infested field showed that T. patula in combination with wheat was responsible for a significantly higher tobacco yield (green leaf mass). In both greenhouse and field trials, cabbage (Brassica oleracea L. var capitata.) proved to be a latent host, suggesting that it should be avoided as a winter cash crop in tobacco fields infested with R. solanacearum.
Open Access
Characterisation of lupin anthracnose caused by Colletotrichum gloeosporioides
(University of the Free State, 2001-11) Ghebremariam, Dawit Solomon; Swart, W. J.; Koch, S.
English: In pathogenicity studies on 14-d-old lupin seedlings, SIX isolates of C. gloeosporioides (collected in 1999 and 2000) showed no pathogenic variation on the 16 lupin cultivars tested compared to an isolate collected in 1995 at the start of the disease outbreak. L. angustifolius cultivars Wonga and Tanjil were consistently more resistant and L. albus cultvars Kiev Mutant, Swartland, CED 6150, Eisa and Vladimir were more susceptible to the seven isolates tested. This suggests that no new virulent isolates of the fungus have appeared in South Africa and that in the short term the cultivation of L. angustifolius cultvars, although L. albus cultivars is preferred, is safe from severe anthracnose attacks in this country. Continuous characterization of isolates and monitoring must however be encouraged in future in order to prevent any potential threats to the local lupin industry. By employing the barley bioassay method of Jones & Varner (1967), gibberellin-like substances were detected in liquid culture from isolates of C. gloeosporioides that cause lupin anthracnose. This is also the first time that gibberellin is associated with a Colletotrichum spp. Its role in the pathogenesis of lupin anthracnose is unknown although some studies have established a correlation between GA3 production and increased disease severity (Sunder et al., 1998) and therefore might be useful for in screening of lupin cultivars for disease resistance. As gibberillins have many modes of action (Salisbury & Ross, 1992) the role of gibberellins in this specific pathogen/host interaction must be investigated. The relationship between GA3 production by the pathogen and the typical twisting and bending of stems and petioles must also be determined. At microscopic level no qualitative differences in conidial germination, appressori urn formation or penetration of the epidermal cell wall by C. gloeosprioides in the very susceptible L. albus cv Kiev Mutant and the less susceptible L. angustifolius cv Wonga were detected. Penetration occurred directly through both the cuticle and. epidermal cell walls. In both cases small spherical vesicles with single primary hyphae were observed in the first penetrated epidermal cells. It will appear that the initial establishment of the pathogen up to vesicle formation is not related to the resistance of lupin cultivars. Post infection hyphal development up to 144 h could not be observed and might be related to an extended biotrophic relationship between the fungus and the host. Furthermore it seems like defense reactions by the plant are only activated after penetration and initial establishment of the pathogen in the host epidermis.
Open Access
Characterization of kenaf (Hibiscus cannabinus L.) cultivars in South Africa
(University of the Free State, 2004-11) Coetzee, Rouxléne; Labuschagne, M. T.
Kenaf (Hibiscus cannabinus L.) is one of the world’s most economically important fibre crops. The traditional use of kenaf focuses on its fibre production, for the making of products such as ropes, sacks, canvases, and carpets. New applications of kenaf have been developed such as pulping and papermaking, board making, filtration media, potting media, animal feed, and oil absorption. The fibres are also processed for use in the automotive industry. Kenaf was introduced to South Africa during the last few years. The crop is being explored as a potential commercial crop for fibre production in South Africa. · The objectives of this study were to conduct glasshouse and field trials on commercial kenaf cultivars to evaluate morphological and agronomic differences between them; to compare the oil content and fatty acid composition of the seed of eight cultivars; to determine genetic relationships between commercial cultivars and nine wild type varieties and to determine the genotype x environment (G x E) interactions and stability of commercial cultivars. · Seeds were obtained from several sources and sown directly into pots. Seedlings were grown in a heat-controlled glasshouse. A field trial was also planted in another location. These plants were used in various investigations. · Two field trials were planted in two different locations to determine the G x E interactions. The experimental designs were complete randomised blocks with four replications. Eight morphological and agronomic characters studied were subjected to an ANOVA and significant differences were found for some traits between cultivars tested in the glasshouse. Significant differences also occurred among replications for some traits in both trials. There were not many morphological differences between cultivars and therefore it is difficult to identify individual cultivars merely by morphological characters. · Seeds of eight cultivars were used to determine the oil content and fatty acid composition of the seed oil. The percentage oil was relatively high for all cultivars; however, there was not much difference between cultivars for oil content. The percentages of each fatty acid varied greatly among different cultivars and therefore there is a potential for genetic improvement in oil quality. · AFLP analysis was used fingerprint commercial cultivars and three wild type varieties. Six primer combinations between EcoR I and Mse I were used to determine genetic relationships. A total of 406 fragments were generated, of which 229 (56.4%) were polymorphic. A low level of genetic diversity was detected in kenaf genotypes. · Separate and combined analyses of variance across locations, three types of stability parameters and correlation analyses were performed. · The separate trial analyses for two locations have shown significant differences among cultivars for three yield traits. With the exception of plant length, there were no significant differences between replications. The combined analysis of variance across locations showed highly significant differences among locations for three yield traits. There were, however, no significant differences among genotypes and their interactions with localities for three traits. All cultivars performed on average better in location 1 (under irrigated conditions) for six measured traits. According to Wricke’s (1962) ecovalence, El Salvador, Everglades 41, and SF 459 were the most stable cultivars for the three yield traits respectively. Lin and Binns’ (1988) cultivar superiority measure indicated that El Salvador and Tainung 2 were the most stable cultivars for the three traits. Nassar and Huehn’s (1987) non-parametric measure of stability revealed that El Salvador and SF 459 had the smallest changes in ranks and thus were the most stable cultivars.
Open Access
Characterization of Opuntia ficus-indica cultivars in South Africa
(University of the Free State, 2002-11) Oelofse, Rachel Mercia; Labuschagne, M. T.; Swarts, W. J.; Viljoen, C. D.
English: Spineless cactus pear [Opuntia ticus-indice (L.) MilL] in South Africa is increasingly commercialised and there is a need to establish a database to assist the South African farmers in the selection of cultivars for production. The aim of this study was to contribute to such a database on horticultural, fodder, genetical and pathoglogical level. 2. Plantmaterial of the 10 cultivars were obtained from a genebank situated near Potgietersrus in the Northern Transvaal (230 50'S), South Africa. This area has a subtropical climate with predominantly summer rainfall. The cultivars were characterised on general horticultural characteristics, characteristics for use as fodder and resistance to four pathogens obtained from infected cactus pear orchards in South Africa. The cultivars were also genetically characterised using the AFLP method. 3. All the morphological results obtained were compared with the genetical data. The results obtained showed that morphological data, whether horticultural, fodder or pathological, are inadequate to distinguish and characterise the different cultivars. DNA fingerprinting can complement this characterisation. 4. The fact that the major clustering in the morphological and pathological dendrograms does not correlate with the AFLP dendrogram proves that low correlation exist between the subset of DNA related to morphological characters, the subset of DNA related to pathology and a random sampling of the total genomic DNA. It also underlines the unreliability of using only morphological and pathological descriptors in selection. In order to solve this problem, further description and characterisation of these cultivars is needed, but in the different cactus pear production areas in South Africa in order to better understand the influence of the environment on these cultivars. Description and characterisation of the cultivars in terms of a wider set of parameters, for instance resistance to a wider range of pathogens and cold tolerance is also needed in order to make the morphological and pathological data more reliable. 5. It is clear from the literature that O. ficus-indice is a multifunctional crop, which can be of great value in both developed en undeveloped countries, because of its ability to utilise the full potential of arid areas, though in South Africa the full potential of cactus pear is not utilised yet. It is clear from the morphological and pathological data in this study that the 10 commercial cultivars in South Africa compare well to other cultivars described in the literature.
Open Access
Chemical composition and antimicrobial activity of different root extracts of Hermannia geniculata against human pathogens of medical importance
(University of the Free State (Qwaqwa Campus), 2015-12) Mojau, Pheello Jeremia; Ashafa, A. O. T.
Hermannia geniculata has been used widely as traditional medicine for treatment agai nst infectious human pathogens. The aim of the study was to determine the antibacterial and anti fungal activities of H. geniculata root extracts and their fractio ns against 16 microbial strains. The dried plant materials were extracted separately in 150 ml of methanol, acetone, ethanol, water and 150 ml (50/50) of hydro-ethanol. Acetone extract inhibited the growth of microorganisms with minimum inhibitory concentration (MIC) values of 1.56 mg/ml against all the tested strains except for Salmonella typhimurium and Candida rugosa at the concentration of 6.25 mg/ml. The ethanol, hydro-ethanol and methanol extracts inhibited bacterial growth with MIC values ranging from3. l 3 mg/ml to 12.50 mg/ml, while water extract had MIC of 12.50 mg/ml against all tested bacterial and fungal strains. Acetone extract had maximum bactericidal concentration (MBC) values ranging from 1.56 to 3.13 mg/ml against most microorganisms. Butanol fraction of acetone extract had MIC of 0.78 mg/ml against Staphylococcus aureus (OK.2b) and Staphylococcus a11re11s (ATCC 6538), whilst the ethyl acetate had the lowest MBC of 1.56 mg/ ml against S. aureus (OK.lb), S. aureus (ATCC 6538), and Streptococcus .faecalis. The extracts and their respective fractions displayed similar inhibitory properties which are indica tions that either the crude extract or their fractions could be used to manage infections assoc iated with bac teria and fungi.
Open Access
Citric acid induced phytoextraction of heavy metals from uranium contaminated soils
(University of the Free State, 2006-11) Scholtz, Ockert Fourie; Potgieter, G. P.; Scholtz, N.
English: Induced phytoextraction is an emerging soil remediation technology that makes use of soil amendments and high biomass crop species to accumulate and remove heavy metals from soils. The failure to rehabilitate an uranium trial mine on Rietkuil 307 in the Karoo Uranium Province of South Africa, has led to above normal concentrations of uranium (U), molybdenum (Mo) and arsenic (As) in topsoil in the vicinity of U ore stockpiles. A greenhouse evaluation was executed to assess the potential of citric acid to induce metal uptake in the shoots of Indian mustard [Brassica juncea (L.) Czern, cultivars: 211000 and 426308] and sunflower (Helianthus annuus L.) to decontaminate the low-level U (28 mg U kg-1 soil), Mo (4.1 mg Mo kg-1 soil) and As (8.9 mg As kg-1 soil) contaminated soil to background concentrations. A further greenhouse study was performed in a soil with high levels of metal concentrations; U (165 mg U kg-1 soil), Mo (125 mg Mo kg-1 soil) and As (49 mg As kg-1 soil), to assess the feasibility of phytoextraction on a high-level metal contaminated soil. Citric acid proved to be effective in enhancing shoot-U, -Mo and -As concentrations and the highest concentrations were observed in B. juncea 211000 (1788 mg U kg-1; 467 mg Mo kg-1; and 24 mg As kg-1) grown in the lowlevel contaminated soil. With a biomass yield of 5.51 tonnes per year for B. juncea 211000, it would take 9 to 14 years to decontaminate Mo and U on Rietkuil 307 soil to background concentrations. As a result of the low As solubility in soil and subsequent low shoot concentrations of the plant species, it is suggested that other measures for As remediation be investigated. Furthermore, plants grown in the high-level contaminated soil achieved considerably lower biomass yields and shoot-metal concentrations than in the low-level soil due to metal toxicity. Phytoextraction will, therefore, not be a feasible remediation technology on high-level U, Mo and As contaminated soils. These results suggest that citric acid induced phytoextraction may provide an environmentally friendly alternative for the decontamination of low-level U and Mo contaminated soils.