Thesis (M. Sc. (Botany)) -- University of the North, 1986 / Refer to the document

Pterocarpus angolensis (kiaat) is one of 20 species of trees in the pantropical genus Pterocarpus. The species occurs in Southern Africa and has a broad distribution over several African countries, including Tanzania, Democratic Republic of Congo, Angola, Zambia, Mozambique, Namibia, Botswana, Zimbabwe and South Africa. The tree is commercially used in several traditional medicinal applications and is well-known as a source of timber for woodcarving and furniture. A single serious disease known as mukwa has been reported on P. angolensis, and the cause has been attributed to the generalist fungus Fusarium oxysporum. Reports of this disease date back to the late 1950s and appear localized in the Livingstone distinct, between Livingstone in Zambia and Bulawayo in Zimbabwe. Recent studies indicate that mukwa disease has begun to subside. There are more recent reports, however, of P. angolensis trees dying in South Africa, in the Mpumalanga Province. The aim of the research presented in this dissertation was to establish the nature of the disease affecting P. angolensis trees in the Mpumalanga Province in South Africa. Trees were sampled from several areas in the province, both from reported disease areas and from areas sustaining healthy trees. Field observations and fungal isolations provided a means to determine whether the disease was attributable to a biotic factor or the result of environmental factors affecting the tree. Isolations concentrated on obtaining species of the Botryosphaeriaceae and of the so-called ophiostomatoid fungi because these fungi are well-known pathogens of trees in the area, have been fairly well studied and the die-back symptoms suggested that they could be involved. The first chapter of this dissertation presents a review of the literature pertaining to P. angolensis, with a focus on mukwa disease. Aspects of the review introduce the genus Pterocarpus, the ecology of the environment wherein P. angolensis occurs and cover the biology of the species. Commercial aspects of the tree as well as the need for conservation are also addressed, providing the foundation for further studies in this dissertation. Many of the symptoms of diseased trees studied were indicative of infection by the Botryosphaeriaceae, a group of several genera of endophytic plant pathogens. These fungi were thus isolated from P. angolensis trees growing in different areas and were subsequently identified. Pathogenicity tests were used to evaluate the possible role that these species might play in the dieback of P. angolensis. Copyright / Dissertation (MSc)--University of Pretoria, 2010. / Microbiology and Plant Pathology / unrestricted

Thesis (M.Phil. (Environmental Law)) --University of Limpopo, 2008 / National Research Foundation, and the SANPAD scholarship

Thesis (MSc)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Pterocarpus angolensis is one of the timber tree species that regenerates naturally in the dry forest of Namibia, mainly assisted by the influence of forest fires. Tree development goes through a prolonged suffrutex stage to reach the sapling stage and then, finally, the bole tree stage. This study focused on assessing the main factors facilitating the development of Pterocarpus angolensis seedlings through the suffrutex stage to the sapling stage in Namibia dry forests. To achieve the study objectives three study locations (Okongo and Ncumcara Community Forests and Caprivi State Forest) were selected, representing a rainfall gradient. Within each study location, two different fire history treatments (recently burnt (RB) and recently unburnt (RU)) were selected, and four plots were randomly selected from each fire history treatment. Face to face individual interviews was conducted with community members surrounding the three forests to obtain indigenous knowledge information about Pterocarpus angolensis tree development. Seedlings and saplings found in all plots were counted and measured (tree height and diameter at breast height (DBH)) while trees more than 3 m high were only counted and measured for DBH. Laboratory analysis was performed to determine basic soil texture and nutrient status. In addition, destructive sampling was done on individual trees in the seedling and sapling stages at each study location. The destructive samples allowed for estimation of biomass in above and below ground components, determination of carbohydrate storage in the taproots and estimation of tree age by counting growth rings on the neck disc of the taproot sample. These measures could shed light on the tree development through the suffrutex stage. The main agents causing Pterocarpus angolensis tree damage and stand disturbances observed are drought, fires, insects, diseases, temperature, lightning, wind, animals and humans. Forest fires were found to be one of the major disturbances in all the study locations, particularly damaging to seedlings when fire intensity is high. Likewise, the most important factors influencing the tree development from seedlings to sapling and sapling to bole tree stages are soil water, soil fertility, plant competition, sunlight and fires. Through counting growth rings of taproot neck discs, it is estimated that the ages of seedlings most commonly range from 5 to 12 years in the dry forests of Okongo, Ncumcara and Caprivi. The soil texture in the three forests is dominated by sand, with the soil reaction usually being moderately acidic while the soils have low levels of organic carbon, phosphorus and exchangeable base cations. This study revealed that Caprivi State Forest (location with the highest rainfall) has the highest stand density followed by Okongo Community Forest and Ncumcara Community Forest with the lowest. Trees were grouped into different DBH and height classes. The highest numbers of trees are found in DBH class 0 – 10 cm and in height class 0.6 – 1.0 m at Okongo Community Forest but at Ncumcara and Caprivi many of the trees are in height class 1.1 – 1.5 m. The mean DBH difference is significant between locations but not significant between fire history treatments. A higher abundance of mature trees are found at Okongo Community Forest while a greater abundance of saplings occur at Ncumcara Community Forest which shows a significant difference between study locations. Seedling abundance is the same across study locations and fire history treatments. The difference in stand structure between study locations appears to be strongly influenced by different management regimes on the three locations. A majority of respondents from all the study locations alleged soil water followed by soil fertility as the main influential factors to Pterocarpus angolensis development. Again, most of the respondents revealed that seedling takes 4 – 7 years to reach sapling stage and their main environmental disturbance is fire. Tree cutting by members of the community was also perceived by the respondents as an important non-environmental disturbance. The most abundant tree development stage perceived by respondents was mature trees while seedlings rated the sparsest stage. Based on the respondents no silvicultural practices are performed to promote Pterocarpus angolensis growth. It follows that the Kiaat trees are currently growing without human intervention that might enhance their development. A combination of social survey (interview) and ecological survey provided reliable information on ecological processes. A weak positive significant correlation relationship existed between shoot mass (aboveground biomass) and taproot mass (belowground biomass), meaning when the taproot mass increases the shoot mass also increases. Analysis of non-structural carbohydrates (NSC) storage in taproots showed that both sugar and starch contents in the taproots could facilitate the survival of the tree during suffrutex stages and its rapid growth thereafter. Based on this study Pterocarpus angolensis regeneration in these three dry forests is poor because seedling abundance is the lowest compared to saplings and mature trees. These study findings can be used as the basis for further studies to predict Pterocarpus angolensis natural regeneration in the dry forests, as well as input when management regimes are being developed for the dry forests of North Namibia. / AFRIKAANSE OPSOMMING: Pterocarpus angolensis (Kiaat) is een van die boomspesies wat natuurlik verjong in die droë bosveld van Namibië, met die hulp van bosbrande. Die boom ontwikkel deur ʼn lang semi-struik stadium waartydens die boompies as saailinge bekendstaan. Daarna ontwikkel dit deur die jongboom stadium tot dit uiteindelik die kroon stadium bereik. Hierdie studie fokus op die faktore bydra tot die ontwikkeling van Pterocarpus angolensis van die semi-struik stadium na die jongboom stadium in die droë bosveld van Namibië. Om die doelstellings van die tesis te bereik is drie studiegebiede gekies langs ʼn reënvalgradiënt (naamlik Okongo en Ncumcara gemeenskapsbosse asook Caprivi Staatsbos). Binne elke studiegebied is twee behandelings met verskillende brandgeskiedenis gekies (gebrand of nie-gebrand in die onlangse verlede). Vier persele is ewekansig uit elk van hierdie behandelings gekies vir eksperimentering. Persoonlike onderhoude is gevoer met gemeenskapslede wat in die omgewing woon ten einde inheemse kennis en inligting te versamel oor die ontwikkeling van die jong Pterocarpus angolensis bome. Alle saailinge en jongbome wat voorkom in die persele is getel en gemeet (boomhoogte en deursnee op borshoogte (DBH)) terwyl bome wat hoër as 3 m is, slegs getel en vir DBH gemeet is. Laboratoriumtoetse is gedoen op grondmonsters ten einde ‘n basiese beskrywing van die grondtekstuur en voedingstofstatus te verkry. Verder is destruktiewe bemonstering toegepas op bome in beide die saailing en jongboom stadium op elke studiegebied. Hierdie bemonstering het dit moontlik gemaak om bogrondse en ondergrondse biomassa te skat, om die opberging van koolhidrate in die penwortels te bepaal, en ook om die boom ouderdom te skat vanaf jaarringe in die nek van die penwortel monster. Hierdie metings kon lig werp op die boomontwikkeling deur die semi-struik stadium. Die faktore wat skade aan Pterocarpus angolensis bome veroorsaak asook versteuring van die opstande waarin die bome voorkom is droogte, brande, insekte, siektes, temperatuur uiterstes, weerlig, wind, diere en mense. Die bevindinge dui op bosbrande as een van die belangrikste versteuringsfaktor in al drie studiegebiede; dit is veral skadelik vir saailinge in die semi-struik stadium wanneer die vuurintensiteit hoog is. Die faktore wat die boomontwikkeling van saailing, na jongboom en kroonstadium beïnvloed is hoofsaaklik grondwater, grondvrugbaarheid, plantkompetisie, sonlig en brande. Die ouderdom van saailinge (bepaal vanaf jaarring tellings in die nek van penwortel monsters) van die meeste saailinge én jongbome is na raming tussen 5 en 12 jaar vir die droë bosse in die studiegebiede van Okongo, Ncumcara en Caprivi. Die grondtekstuur van hierdie studie se drie bosgebiede is hoofsaaklik sanderig, met ’n effens suur grondreaksie terwyl die gronde lae vlakke van organiese koolstof, fosfor, en uitruilbare basiese katione bevat. Die studie het aangedui dat Caprivi staatsbos (met die hoogste reënval) die digste opstande huisves, gevolg deur Okongo en dan Ncumcara gemeenskapsbos, met die laagste digtheid. Bome is gegroepeer in verskillende DBH en hoogte klasse. Die meeste bome kom voor in die DBH klas van 0-10 cm en in die hoogteklas van 0.6 – 1.0 m by Okongo, maar by Ncumcara en Caprivi is daar meer bome in die hoogteklas van 1.1 - 1.5 m. Die gemiddelde DBH verskil is betekenisvol tussen studiegebiede, maar is nie betekenisvol verskillend tussen brandgeskiedenis behandelings nie. ’n Hoër voorkoms van volwasse bome is by Okongo aangetref, terwyl ’n hoër voorkoms van jongbome by Ncumcara waargeneem is, en hierdie verskil was statisties betekenisvol. Die voorkoms van saailinge is soortgelyk oor alle studiegebiede en brandgeskiedenis behandelings heen. Die verskil in die struktuur van die opstande op die drie studiegebiede word skynbaar sterk beïnvloed deur verskillende bestuurspraktyke wat in elke gebied toegepas word. Die meerderheid van respondente van al drie studiegebiede beweer dat grondwater, gevolg deur grondvrugbaarheid die belangrikste faktore is wat P. angolensis ontwikkeling beïnvloed. Meeste van die respondente onthul dat saailinge 4 tot 7 jaar neem om die jongboom stadium te bereik en dat die belangrikste versteuringsagent bosbrande is. ʼn Belangrike nie-omgewingsfaktor wat verantwoordelik is vir versteuring in die bosse is mense wat bome, lote en/of takke afsaag. Respondente is van mening dat volwasse bome die grootteklas met die mees algemene voorkoms is, terwyl saailinge die skaarsste grootteklas uitmaak. Die respondente het aangedui dat geen boskultuurpraktyke toegepas word om die groei van P. angolensis aan te help nie. Die gevolgtrekking is dus dat die Kiaatbome tans groei sonder menslike ingryping om hul ontwikkeling te verbeter. Die kombinasie van persoonlike onderhoude en ʼn ekologiese opnames het betroubare inligting rakende ekologiese prosesse opgelewer. ’n Swak positiewe, maar betekenisvolle korrelasie bestaan tussen die massa van die bogrondse lote en die penwortelmassa, wat beteken dat die lote se massa toeneem met toenemende wortelmassa. Analise van opgebergde nie-strukturele koolhidraatreserwes in die penwortel toon dat beide suiker- én styselinhoud in die penwortels die oorlewing van die boom in die struikstadium aanhelp, asook sy vinnige groei na die struikstadium. Die feit dat die saailinge minder volop is as jongbome en volwasse bome in hierdie studie dui aan dat verjonging van Pterocarpus angolensis in hierdie droë bosse maar swak is. Die bevindinge van die studie bevat inligting wat gebruik kans word (a) as die grondslag van verdere studies op die natuurlike verjonging van Pterocarpus angolensis in droë bosse, en (b) as inset wanneer bestuursaanbevelings vir die droë bosse van Noord Namibië ontwikkel word.

La phaeoramulariose des agrumes (Pseudocercospora angolensis) attaque les agrumes en Afrique tropicale et constitue une menace pour les autres pays producteurs situés en zone tropicale. La lutte chimique est le seul moyen de lutte efficace contre cette maladie. Cependant, elle est couteuse et néfaste pour l'environnement. La mise en place de stratégies de lutte permettant de minimiser l'emploi de fongicides contre est donc nécessaire. La connaissance des facteurs de risque de la phaeoramulariose est une étape préliminaire à cette démarche. Le travail entrepris avait pour but de préciser, à l'aide d'une enquête et des expérimentations, les effets de certains facteurs sur le développement de la maladie. L'enquête a été effectuée dans 39 sites de production des agrumes au Cameroun. Elle a permis de recenser les facteurs pédoclimatiques et biologiques dans l'environnement des arbres et de retenir les plus importants dans l'épidémiologie. Les expérimentations sur 8 sites ont permis de confirmer et évaluer les paramètres retenus après l'enquête. L'altitude, le type de sol, l'espèce d'agrumes et le type de végétation ont été retenus comme principaux facteurs de développement de la maladie. Les relations entre ces facteurs et l'incidence de la maladie sont illustrées dans les arbres de segmentation. Les expérimentations ont confirmé la grande sensibilité des pomélos et orangers vis-à-vis P. angolensis. En revanche, les mandariniers et la lime Tahiti se sont avérés moins sensibles. L'incidence de la maladie augmente avec une élévation en altitude, une diminution de la température et de la pluviométrie. La texture du sol s'est avérée plus déterminante du niveau de la maladie que sa composition. Le rôle de l'ombrage s'est avéré déterminant sur l'incidence de la maladie. L'analyse de la structure spatiale de la maladie a permis de mettre en évidence une structure agrégée. La structure spatiale des sous populations de familles d'arbres d'une parcelle agroforestière était aussi agrégée. La dispersion de la phaeoramulariose au sein d'une telle parcelle entre les différents agrégats d'agrumes serait limitée. L'analyse de régression a permis de déceler des différences entre les paramètres contribuant au développement de la maladie sur pomélos, satsuma et orangers. La possibilité d'une conception des systèmes agroforestiers raisonnés pour diminuer la pression des bioagresseurs est envisagée. / Phaeoramularia leaf and fruit spot disease of citrus (PLFSD) caused by Pseudocercospora angolensis attacks citrus in tropical Africa. It also constitutes a threat for the other producer countries located in tropical zone. Chemical treatment is the only method used for effective control of this disease. However, in addition to causing ecological problems, this method lies beyond the reach local smallholders. The development of ecologically friendly strategies to ensure effective protection of citrus is thus necessary. To this end, knowledge of PLFSD risk factors is pre-required. The purpose of this study was to specify, by means of a survey and experiments carried, the effects of certain biotic and abiotic factors on the development of the disease. The survey carried out in 39 production sites of Cameroon, targetted a collection of environmental and biological tree characteristics. Experiments on 8 sites enabled a confirmation and evaluation of suspected factors. A stepwise logistic regression analysis of survey data made it possible to target altitude, soil type, citrus species and vegetation type as main factors influencing disease development. Relations between these factors and disease incidence are illustrated in segmentation trees. Experiments confirmed the great sensitivity of grape fruit and orange trees, while tangerine and Tahiti lime trees were less sensitive. Disease incidence increased with a rise in altitude and a reduction in temperature and rainfall. Soil texture proved to be more determinant in disease development than its chemical composition. Experimentation showed that trees planted under shade are less affected than those located in sunshine. A spatial structure analysis of the disease made it possible to highlight an aggregate structure indicating small scale disease dispersion. An analysis of the spatial structure of an agro forestry farm showed an aggregate structure of the sub populations of constituent tree families. This structure suggested that the dispersion of PLFSD within such a farm would be limited between the various citrus aggregates. PLS regression analysis suggested that several of these parameters play a determinant role in contributing to the development of disease on grape fruit, orange and Satsuma mandarin trees. The development of integrated agro forest systems which enable a decrease of the pressure of pest and diseases is envisaged.

Submitted by Cleide Dantas (cleidedantas@ufpa.br) on 2014-05-06T16:24:27Z No. of bitstreams: 2 license_rdf: 23898 bytes, checksum: e363e809996cf46ada20da1accfcd9c7 (MD5) Dissertacao_AnaliseComunicacaoSonora.pdf: 5705448 bytes, checksum: bf95b02d994c05dc18624aff8eb4172a (MD5) / Approved for entry into archive by Ana Rosa Silva (arosa@ufpa.br) on 2014-07-14T17:01:40Z (GMT) No. of bitstreams: 2 license_rdf: 23898 bytes, checksum: e363e809996cf46ada20da1accfcd9c7 (MD5) Dissertacao_AnaliseComunicacaoSonora.pdf: 5705448 bytes, checksum: bf95b02d994c05dc18624aff8eb4172a (MD5) / Made available in DSpace on 2014-07-14T17:01:40Z (GMT). No. of bitstreams: 2 license_rdf: 23898 bytes, checksum: e363e809996cf46ada20da1accfcd9c7 (MD5) Dissertacao_AnaliseComunicacaoSonora.pdf: 5705448 bytes, checksum: bf95b02d994c05dc18624aff8eb4172a (MD5) Previous issue date: 2011 / CNPq - Conselho Nacional de Desenvolvimento Científico e Tecnológico / O Curió Oryzoborus angolensis (Aves, Passeriformes, Oscines, Emberizinae) é uma espécie Neotropical muito conhecida e apreciada entre os criadores de pássaros no Brasil, por possuir canto melodioso e variado. O canto tem como função biológica o reconhecimento específico. A presença de repertórios vocais longos, variações populacionais e individuais pode ser um indicativo de aprendizagem vocal, que é o caso do Oryzoborus angolensis. O repertório representa os diferentes tipos de unidades que constituem o canto, as notas, emitidas durante a vocalização. No caso do canto do Curió a frase pode ser caracterizada como uma sequência de notas que se repetem. Analisamos as amostras de gravações de 26 indivíduos, sendo dezesseis de cativeiro e dez selvagens provenientes de diversas localidades do país. Identificamos e denominamos cada uma das 2414 notas gravadas com uma letra do alfabeto. As medidas dos parâmetros físicos das notas (duração, intervalo entre as notas, ritmo, frequência máxima e frequência mínima) apresentaram diferenças globais significativas, podendo ser um dos caracteres responsáveis pela função de reconhecimento específico. Observamos que as notas são constituídas principalmente por sons puros e amplamente moduladas, distribuídas de forma homogênea na amostra. Descrevemos a estrutura do canto, com a análise do repertório dos indivíduos de cativeiro e selvagem, apresentado diferenças estatisticamente significativas entre si. Considerando a distribuição dos diferentes tipos de notas emitidas por indivíduos,calculamos a entropia informacional, que forneceu um índice que correspondente à previsibilidade do canto individual. / The Seed-finch Oryzoborus angolensis (Aves, Passeriformes, Oscines, Emberizinae) is very a popular and appreciated species birdkeepers in Brazil, due to its melodious and varied song. The song represents the species-specific recognition signal for the most of the birds. Songs with long vocal repertoires, population and individual variations can be indicatives of vocal learning. In this context, we studied the song of the Lesser seed finch Oryzoborus angolensis. The song of O. angolensis is characterized as a sequence of pure notes organized and repeated in discrete phrases. We analyze the song of 26 individuals, 16 in captivity and 10 wild from different localities of their distribution area. The measures of physical parameters of the notes (note duration, note interval, rhythm, minimum and maximum frequency) presented significant global differences, considered here the characters that represents the species-specific code. We observe that the notes are constituted mainly by widely modulated pure sounds and are distributed in homogeneous way in our sample. We have found significant differences between the repertoire of the individuals kept in captivity and wild.

Thesis (MScAgric)--University of Stellenbosch, 2005. / ENGLISH ABSTRACT: Fruit and Leaf Spot Disease (FLSD) of citrus, caused by Phaeoramularia angolensis, is found only in 18 countries in Africa, the Comores Islands in the Indian Ocean and Yemen in the Arabian peninsula. The major citrus export countries in Africa are Morocco, South Africa, Swaziland, and Zimbabwe. Zimbabwe is the only country affected by FLSD. FLSD is a disease of major phytosanitary and economic importance and its devastating effect on citrus is highlighted by the fact that the damage is cosmetic, which renders the fruit unmarketable. Total crop losses are not uncommon in Kenya. The aims of the present study, therefore, was was to determine the occurrence of P. angolensis in Zimbabwe and neighbouring Mozambique, to compare these isolates with the Cercospora Fresen. isolates from Swaziland and South Africa, to determine the epidemiology of the pathogen and to implement an effective control strategy to prevent the spread of FLSD. Leaf samples with citrus canker-like lesions collected in the early 1990’s in Zimbabwe were found to be infected by the fungus, Phaeoramularia angolensis. Surveys were undertaken to determine the spread and intensity of FLSD in Zimbabwe and Mozambique. In Zimbabwe, P. angolensis was limited to an area above the 19° south latitude, predominantly the moist areas and not the low-lying drier parts of the country. In Mozambique, no P. angolensis symptoms were found. Observations during the survey indicated that no proper management systems were implemented by Zimbabwean growers. A cercosporoid fungus causing a new Fruit and Leaf Spot Disease on Citrus in South Africa was identified. From morphological and rDNA sequence data (ITS 1, 5.8S and ITS 2), it was concluded that the new disease was caused by Cercospora penzigii, belonging to the Cercospora apii species complex. The genera Pseudophaeoramularia and Phaeoramularia are regarded as synonyms of Pseudocercospora, and subsequently a new combination was proposed in Pseudocercospora as P. angolensis. Cercospora gigantea was shown to not represent a species of Cercospora, while Mycosphaerella citri was found to be morphologically variable, suggesting that it could represent more than one taxon. A control strategy for the control of FLSD was evaluated in the study. The data showed that P. angolensis in Zimbabwe can be managed successfully by the removal of all old and neglected orchards, and on timely fungicide applications. Trifloxystrobin + mancozeb + mineral spray oil (20 g + 200 g + 500 ml/100 l water) applied in November, January and March was the most effective treatment. Three applications of benomyl + mancozeb + mineral spray oil (25 g + 200 g + 500 ml/100 l water) applied during the same period, was the second most effective treatment, and two applications (November and January) of trifloxystrobin + mineral spray oil (20g + 500 ml/100 l water) and difenoconazole (40 g) per 100 l/water applied twice in November and January, the third most effective treatment. The spore trap and weather data showed that P. angolensis needs high moisture and temperatures in excess of 25°C for disease development. It is concluded that P. angolensis in Zimbabwe can be managed successfully by implementing a holistic approach, which should be supported by the authorities, organised agriculture and all technical personnel involved in citrus production. / AFRIKAANSE OPSOMMING: Blaar- en vrugvleksiekte (BVVS) op sitrus, veroorsaak deur Phaeoramularia angolensis, kom in 18 lande in Afrika voor asook die Comores Eilande in die Indiese Oseaan en Yemen op die Arabiese skiereiland. Marokko, Suid Afrika, Swaziland en Zimbabwe is die belangrikste uitvoerders van sitrus in Afrika. Van dié lande het slegs Zimbabwe blaar en vrugvleksiekte op sitrus. Hierdie siekte is van fitosanitêre en ekonomiese waarde en die nadelige effek van die siekte, wat slegs kosmetiese van aard is, is venietigend aangesien vrugte onbemarkbaar is. Totale opbrengsverliese is nie ongewoon in lande soos Kenya nie. Die doelwitte van die studie was dus om die voorkoms van P. angolensis in Zimbabwe te bepaal, om die Cercospora Fresen. isolate vanaf Swaziland en Suid-Afrika met mekaar te vergelyk, om die epidemiologie van die siekte vas te stel en om ‘n effektiewe beheermaatreël teen die siekte te ondersoek. Blaarmonsters met kankeragtige letsels wat in die vroeë 1990’s in Zimbabwe gevind is, het getoon dat die blare geinfekteer is met die swam, Phaeoramularia angolensis. Ondersoeke is geloots om die verspreiding en intensiteit van BVVS in Zimbabwe en Mosambiek te bepaal. In Zimbabwe was gevind dat P. angolensis beperk was tot gebiede bo die 19° Suid breedtegraad, wat die hoër vogtiger gebiede insluit eerder as die droeër, laagliggende gebiede. Geen P. angolensis simptome kon in Mosambiek gevind word nie. Tydens die opnames was dit duidelik dat geen geskikte beheerstrategieë toegepas word deur Zimbabwe se produsente nie. ‘n Nuwe cercosporoid swam, wat blaar en vrugvleksiekte op sitrus is in Suid Afrika veroorsaak is geidentifiseer. Morfologiese en rDNA volgorde (ITS 1, 5.8S en ITS 2) data het getoon dat die siekte veroorsaak word deur Cercospora penzigii wat tot die Cercospora apii spesie kompleks behoort. Die genus Pseudophaeoramularia kan as sinoniem van Pseudocercospora beskou word en ‘n nuwe kombinasie word voorgestel in Pseudocercospora as P. angolensis. Cercospora gigantea het getoon dat dit nie ‘n spesie van Cercospora kon verteenwoordig nie terwyl Mycosphaerella citri varieërend voorkom en meer as een takson kan verteenwoordig. ‘n Beheerstrategie vir die beheer van BVVS is ondersoek. Die data wys dat P. angolensis in Zimbabwe doeltreffend beheer kan word deur die uitroeiing van ou en verwaarloosde bome, en deur goed beplande fungisied bespuiting. Trifloxystrobin + mancozeb + minerale spuitolie (20 g + 200 g + 500 ml/100 l water), wat in November, Januarie en Maart toegedien is, was die mees effektiefste behandeling. Drie bespuitings van benomyl + mancozeb + minerale spuitolie (25 g + 200 g + 500 ml/100 l water) wat oor dieselfde tydperk toegedien is, was die naas beste behandeling. Trifloxystrobin (20 g) + minerale spuitolie (500 ml) per 100 l/water en difenoconazole (40 g) per 100 l/water, beide as twee bespuitings toegedien in November en Januarie, het die derde beste resultaat opgelewer. Die spoorlokval en klimatologiese data het getoon dat P. angolensis vogtige toestande en temperature hoër as 25°C benodig vir siekteontwikkeling. Die afleiding uit die studie is dat P. angolensis suksesvol beheer kan word indien ‘n holistiese benadering gevolg word en alle rolspelers naamlik die owerheid, georganiseerde landbou en tegniese personeel die proses ondersteun.

Thesis (M.Sc. (Microbiology)) --University of Limpopo, 2011 / Pterocarpus angolensis seed lectin (PAL), a 28 kDa non glycosylated protein, was initially successfully cloned and expressed in E. coli for ease of high protein production. It was discovered, however, as in similar studies that the recombinant PAL yield in E. coli is low and localized intracellularly. This makes extraction even more difficult because most of the protein is lost either when the cell undergoes lysing or when there is incomplete extraction. As a result of the low yields in E. coli, expression vectors were constructed for pal expression in S. cerevisiae, Y. lipolytica and A. niger. Colony PCR of S. cerevisiae transformants confirmed the presence of pal gene whilst sequencing revealed a 66% homology to native PAL. Expression of recombinant PAL in S. cerevisiae, which was expected to be intracellular, was doubtfully unsuccessful since no signal was detected following Western blot analysis. A pBARMTE1-pal expression vector was successfully constructed and could be used for expression studies in Aspergillus niger, however, it was not used in this study. A pal gene whose codons were optimized for Y. lipolytica was synthesized and successfully cloned and expressed in Y. lipolytica. Gene sequence alignment of native pal and the codon optimized pal showed 81% homology whilst the amino acid alignment showed 100% homology. A 31 kDa, recombinant PAL was successfully expressed in Y. lipolytica. The recombinant PAL was approximately 3 kDa larger than native PAL. It was established that this is due to glycosylation of the recombinant PAL. This recombinant protein was found to be more thermostable than native PAL since it demonstrated haemagglutination activity after 10 minutes of exposure in a boiling water bath and only lost activity after 2 hours of exposure to boiling. This study succeeded in producing a more stable extracellular recombinant PAL which demonstrated biochemical activity that was largely similar to that of native PAL but only differed in carbohydrate specificity and haemagglutinating strengths. / Flemish Interuniversity Council (VLIR-UOS)-Own Initiative Project,the SARBIO- South African Regional Co-operation in Biochemistry, Molecular Biology and Biotechnology, the (CSIR) Council for Scientific and Industrial Research,the (NRF) National Research Foundation,(TBI) The Biovac Institute Foundation, and the (SIDA) Swedish International Agency

Thesis (MScFor)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Kiaat trees in Namibia are threatened by unsustainable harvesting practice. This study’s aim was to estimate the total value of an average Kiaat tree selected for harvesting with a focus on current timber use value, value of an optimally utilised tree, carbon value, and alternative uses of Kiaat trees. To accomplish this aim, the following specific objectives were set: (1) to estimate the total tree volume and optimum utilisable timber volume of an average Kiaat tree; (2) to estimate the amount and value of carbon stored in the above-ground parts of an average Kiaat tree; (3) to determine timber utilisation levels; and (4) to identify alternative use options to reduce timber losses of Kiaat trees. Previous studies on Kiaat in Namibia and elsewhere focused on growth, development and socio-economical aspects of Kiaat trees. A combination of a socio-economic survey and tree volumes and biomass determination was used to collect data. The survey entailed Kiaat products assessment and face-to-face personal interviews with known key-informants in and around Rundu. Loggers with permits to harvest Kiaat trees were asked to harvest 40 Kiaat trees and data collected from each tree before and after felling included: lower-stem diameter, diameter at breast height (DBH), upper-stem diameter, stem length, stump height, recovered merchantable logs lengths and lower-and-upper diameters and lengths of branches greater than 10 cm in diameter. All canopy parts smaller than 10 cm in diameter were directly weighed, sampled and oven-dried at 105°C until constant weight. Volume of different tree parts was calculated and in combination with basic wood density used to calculate the biomass. It was established that a typically harvested Kiaat tree had an above-ground dry volume of 1.63 m3, of which 1.34 m3 (82%) was utilisable timber volume but that only 0.37 m3 (23%) was used and 0.97 m3 (59%) was left behind in the field. Merchantable logs were mainly cut into planks from which finished products - beds, chairs, doors and tables - were made. An average of 10.7 planks were cut per trunk and the local price of planks was N$45.26 at the time of the study. More income is generated from finished products compared to selling loose planks. Canopy parts were mainly cut into woodcrafts – bowls, music drums, and walking sticks. Current timber use value (N$484.73) surpasses carbon value (N$123.74). A further result of the study was that a significantly higher income could be earned for local livelihoods from Kiaat trees in the Kavango Region if trees were optimally used. Carbon trading is a noble conservation initiative, particularly when trees unsuitable for timber are considered. Use of timber trees exclusively for carbon trading is, however, not a viable option in respect of supporting local people’s livelihoods. / AFRIKAANSE OPSOMMING: Kiaatbome in Namibië word bedreig deur onvolhoubare ontginningspraktyke. Die doelwit van die studie was om die totale waarde van ‘n gemiddelde Kiaatboom, wat gekies is vir ontginning, te bepaal met die fokus op huidige houtwaarde, waarde van ‘n optimaal gebruikte boom, koolstofwaarde en alternatiewe gebruike vir Kiaatbome. Om hierdie doelwit te bereik is die volgende spesifieke sub-doelwitte gestel: (1) bepaal die totale boomvolume en optimale bruikbare houtvolume van ‘n gemiddelde Kiaatboom; (2) bepaal die hoeveelheid koolstof wat in die bogrondse dele van ‘n gemiddelde Kiaatboom gestoor word en bereken die monitêrewaarde daarvan; (3) bepaal die houtgebruiksvlakke en houtvermorsing van Kiaatbome; en (4) identifiseer alternatiewe gebruike om die vermorsing van Kiaatbome te verminder. Vorige studies oor Kiaat in Namibië en elders het gefokus op groei, ontwikkeling en sosio-ekonomiese aspekte van Kiaatbome. ‘n Kombinasie van ‘n sosio-ekonomiese opname en boomvolume en biomassa bepalings is gebruik vir die insameling van data. Die opname het ‘n Kiaat produkbepaling en gesig-tot-gesig persoonlike onderhoude met sleutel informante in en om Rundu behels. Boomkappers met permitte om kiaatbome te ontgin is gevra om 40 Kiaatbome te ontgin en data is versamel van elke boom voor en na ontginning. Die data het ingesluit: lae-stam deursnee, deursnee op borshoogte (DBH), bo-stam deursnee, stamlengte, stomphoogte, herwinde bruikbare stomplengte, bo- en onder- deursnee en lengtes van takke wat 10 cm of groter deursnee het. All kroondele 10 cm en kleiner in deursnee is geweeg en ‘n steekproef versamel wat oondroog gemaak is by 105ºC totdat konstante gewig bereik is. Die volume van verskillende boomdele is bereken en in kombinasie met houtdigtheid gebruik om biomassa te bereken. Dit is bereken dat ‘n tipiese geoeste Kiaatboom ‘n bogrondse droë volume van 1.63 m³ het, waarvan 1.34 m³ (82%) bruikbare houtvolume is. Net 0.37 m³ (23%) van die bruikbare houtvolume is egter gebruik en 0.97 m³ (59%) is agtergelaat in die veld. Bruikbare stompe is meestal opgesaag in planke waarvan finale produkte soos beddens, stoele, deure en tafels gemaak is. ‘n Gemiddeld van 10.7 planke is verkry per stomp en die plaaslike prys van planke was N$45.26 gedurende die studie tydperk. Meer inkomste is verkry van finale produkte as van die verkoop van los planke. Kroondele is meestal opgesaag in houtkunswerke soos bakke, musiekdromme en kieries. Die huidige houtwaarde van N$484.73 is meer as die koolstof waarde (N$123.74) van die bome. ‘n Belangrike resultaat van die studie is dat ‘n beduidende groter inkomste gegenereer kan word vir plaaslike lewensbestaan van Kiaatbome in die Kavangostreek as bome optimaal benut word. Koolstofhandel is ‘n edele bewaringskonsep, veral as bome ongeskik vir houtgebruik is soos in die geval van krom bome en jonger bome. Die eksklusiewe gebruik van houtbome vir koolstofhandel is nie ‘n lewensvatbare opsie om plaaslike mense se lewensbestaan te ondersteun nie.