Diseases assosiated with plantation forestry in Uganda

Please read the abstract (Summary) in the section 00front of this documentDissertation (MSc)--University of Pretoria, 2005.Microbiology and Plant PathologyUnrestricte

Efficiency of natural wood extractives as wood preservatives against termite attack

Wood extractives play a major role in the protection of wood against termite and fungal attack. Wood extractives from three hard wood species of Milicia excelsa, Albizia coriaria and Markhamia lutea that are known to be very resistant against termite attack and fungal decay were studied to assess their role as wood preservatives in Uganda. Acetone, hexane and distilled water were used in the extraction of these compounds from the outer heartwood of the selected durable species. Extraction was done using a soxhlet extractor. The extractives obtained were used to treat Pinus caribaea and Antiaris toxicaria species known to be susceptible to termites and fungal attack. Treated blocks were then exposed to Macrotermes bellicosus termites in the fi eld. It was observed that wood extracts used as preservatives improved the resistance of less durable samples to termite attack by 50% compared to the controls. It was also observed that removal of extractives decreased resistance of the durable samples. It can be concluded that wood extractives contribute greatly to the protection of less durable wood species against termite attack

Celoporthe dispersa gen. et sp. nov. from native Myrtales in South Africa

In a survey for Cryphonectria and Chrysoporthe species on Myrtales in South Africa, a fungus resembling the stem canker pathogen Chrysoporthe austroafricana was collected from native Syzygium cordatum near Tzaneen (Limpopo Province), Heteropyxis canescens near Lydenburg (Mpumalanga Province) and exotic Tibouchina granulosa in Durban (KwaZulu-Natal Province). The fungus was associated with dying branches and stems on S. cordatum, H. canescens and T. granulosa. However, morphological differences were detected between the unknown fungus from these three hosts and known species of Chrysoporthe. The aim of this study was to characterise the fungus using DNA sequence comparisons and morphological features. Pathogenicity tests were also conducted to assess its virulence on Eucalyptus (ZG 14 clones), H. natalensis and T. granulosa. Plants of H. canescens were not available for inoculation. Results showed distinct morphological differences between the unknown fungus and Chrysoporthe spp. Phylogenetic analysis showed that isolates reside in a clade separate from Chrysoporthe and other related genera. Celoporthe dispersa gen. et sp. nov. is, therefore, described to accommodate this fungus. Pathogenicity tests showed that C. dispersa is not pathogenic to H. natalensis, but that it is a potential pathogen of Eucalyptus and Tibouchina spp

Genetic control of Eucalyptus urophylla and E. grandis resistance to canker caused by Chrysoporthe cubensis

Chrysophorte cubensis induced canker occurs in nearly all tropical and subtropical regions where eucalypts are planted, causing losses in both wood quality and volume productivity, especially so in the warmer and more humid regions of Brazil. The wide inter and intra-specific genetic variability of resistance to canker among Eucalyptus species facilitates the selection of resistant plants. In this study, we evaluated resistance to this pathogen in five Eucalyptus grandis (G) and 15 E. urophylla (U) trees, as well as in 495 individuals from 27 progenies derived from crosses between the trees. In the field, six-months-old test seedlings were inoculated with C. cubensis. Lesion length in the xylem and bark was measured eight months later. The results demonstrated that xylem lesions could preferentially be used for the selection of resistant clones. Eight trees (7 U and 1 G) were susceptible, and the remainder (8 U and 4 G) resistant. Individual narrow and broad sense heritability estimates were 17 and 81%, respectively, thereby suggesting that canker resistance is quantitative and highly dependent on dominance and epistasis

A gender gap in construction : Barriers to gender equality

Sweden has made enormous progress when it comes to gender equality hence its ranking as first among other states with a score of 83.9 percent. Despite all the progress, there are still challenges that create a huge gender gap in gender-based professions where some professions are considered male whereas others are termed female. It is obvious that gender segregation still prevails in occupations that are traditionally gendered. The purpose of this study was to identify barriers within the construction industry that are maintaining the gender gap and frustrating Sweden's efforts to steer towards a complete gender equality. The study was analysed based on three theories, glass ceiling (Blackwell ,2017), gender theory (Connell (1996) Simone de Beauvoir, 1949) and gender system (Yvonne Hirdman, 1988) as the main theory. Seven interviews with five women in the construction industry were conducted. Discrimination in working hours, pay gap, sexual harassment, lack of role models are some of the barriers that this report highlights. The findings show that the gender gap is generated by macho culture, male superiority and firmly ingrained masculine norms as well as beliefs.

A gender gap in construction : Barriers to gender equality

Sweden has made enormous progress when it comes to gender equality hence its ranking as first among other states with a score of 83.9 percent. Despite all the progress, there are still challenges that create a huge gender gap in gender-based professions where some professions are considered male whereas others are termed female. It is obvious that gender segregation still prevails in occupations that are traditionally gendered. The purpose of this study was to identify barriers within the construction industry that are maintaining the gender gap and frustrating Sweden's efforts to steer towards a complete gender equality. The study was analysed based on three theories, glass ceiling (Blackwell ,2017), gender theory (Connell (1996) Simone de Beauvoir, 1949) and gender system (Yvonne Hirdman, 1988) as the main theory. Seven interviews with five women in the construction industry were conducted. Discrimination in working hours, pay gap, sexual harassment, lack of role models are some of the barriers that this report highlights. The findings show that the gender gap is generated by macho culture, male superiority and firmly ingrained masculine norms as well as beliefs.

A study of Chrysoporthe and Cryphonectria species on Myrtales in southern and eastern Africa

Considerable changes have occurred in recent years, regarding the taxonomy and ecology of Eucalyptus fungal pathogens previously treated in the genera Cryphonectria and Endothia. Cryphonectria cubensis now resides in Chrysoporthe with two species, which are very distinct from Cryphonectria. The fungus previously known as E. gyrosa was moved to C. eucalypti and will soon be known as Holocryphia eucalypti. It is very likely that C. eucalypti and Chr. cubensis were introduced onto the African continent, but the hypothesis remains to be tested, while Chr. austroafricana seems native to the African continent. The aim of studies contained in this thesis was to consider the distribution, taxonomy and diversity of Chrysoporthe spp. and Cryphonectria eucalypti on the African continent. This was achieved through surveys in southern and eastern Africa, of both Eucalyptus spp. and native tree species belonging to the Myrtales. The intention was that the results of the studies in this thesis should aid in a better understanding of the taxonomy, origin, distribution, host range, as well as pathogenicity of various Cryphonectria and Chrysoporthe species in eastern and southern Africa. Various new hosts, new areas of occurrence and taxonomic changes have occurred for species of Cryphonectria sensu lato, previously known only on Eucalyptus spp. Chapter one of this thesis presented an overview of the most recent findings regarding the taxonomy, host range and distribution of C. cubensis sensu lato and C. eucalypti. The background to the description of a new genus, Chrysoporthe Gryzenhout&M.J. Wingf. and three new species namely; Chr. cubensis, Chr. austroafricana and Chrysopothella hodgesiana, previously considered to represent C. cubensis was also considered. Furthermore, the wide host range of Chrysoporthe spp. has been reviewed. The fungi are known on various genera in the order Myrtales in both tropical and subtropical areas, worldwide. Emphasis was placed on these Eucalyptus pathogens in Africa. Chrysoporthe cubensis and Chr. austroafricana, collectively known as Cryphonectria cubensis in the past, are important canker pathogens of Eucalyptus spp. worldwide. In chapter two of this thesis I have shown, for the first time, that Chr. cubensis occurs in Kenya, Malawi and Mozambique on non-native Eucalyptus spp. and Chr. austroafricana occurs in Mozambique, Malawi and Zambia on non-native Eucalyptus spp. and native S. cordatum. I was also able to show that Chr. austroafricana causes cankers at the base and higher up on stems of Eucalyptus trees in South Africa and Malawi, which is contrary to prior knowledge. Likewise, the sexual state of this fungus has been shown to be equally abundant as the asexual state in countries north of South Africa, contrary to the situation in southern Africa where the asexual state predominates. The known distribution range of Chr. austroafricana within South Africa was also expanded through this study. Chrysoporthe cubensis is an important fungal pathogen of Eucalyptus spp., worldwide. The fungus is also known on many other hosts all residing in the order Myrtales. Previous surveys conducted in eastern and southern Africa to assess the distribution of Chrysoporthe spp. in this region, revealed the occurrence of Chr. cubensis on Eucalyptus spp. in Kenya, Malawi and Mozambique. In chapter three of this thesis, the population structure of Chr. cubensis isolates from Eucalyptus spp. from Kenya, Malawi and Mozambique was considered for the first time. This represents a first attempt to consider the genetic structure of the fungus from eastern Africa. Results show that there is a very low genetic diversity within the populations of Chr. cubensis from Kenya, Malawi and Mozambique, implying that the fungus is probably newly introduced in these areas. Based on phylogenetic analyses, the origin of eastern African Chr. cubensis is most likely Asia. In chapter four of this thesis, polymorphic microsatellite DNA markers were developed from a single spore isolate of C. eucalypti collected from Eucalyptus stem canker in South Africa. Markers were obtained using the enrichment technique known as FIASCO (Fast Isolation by AFLPs of Sequences Containing Repeats). Ten polymorphic markers were isolated, of which 2 were discarded due to their high polymorphism in the flanking region. These markers will consequently provide useful tools for future investigations considering the population biology and especially the global spread of C. eucalypti. Cryphonectria eucalypti is a fungal pathogen considered opportunistic in South Africa, while in Australia it has been associated with sporadic but serious disease problems. Chapter five of this thesis presents results on the population structure of C. eucalypti from South Africa, eastern and western Australia. Nei's gene diversity (H) showed that the eastern Australian population is most genetically diverse and the western Australian populations from Corymbia and Eucalyptus somewhat less diverse. The South African population displayed the lowest genetic diversity. The high genetic diversity in the Australian populations supports the view that C. eucalypti is native to that region. This is consistent with the fact that Eucalyptus species are also native to the Australian continent. In chapter six of this thesis, I have shown that the fungus isolated from H. canescens, S. cordatum and T. granulosa in South Africa represents a new genus and species related to, but distinctly different from Chrysoporthe. Celoporthe dispersa gen. et sp. nov. is, therefore, described to accommodate this fungus. This description was supported by both morphological characteristics and DNA sequence data. These have clearly shown that isolates of C. dispersa form a clade distinct from Chrysoporthe, Holocryphia and other taxa, which it resembles morphologically. Pathogenicity tests showed that C. dispersa is not pathogenic to H. natalensis, but a potential pathogen of Eucalyptus and Tibouchina spp. The collection of studies included in this thesis demonstrated that Chrysoporthe spp. occur in Malawi, Mozambique, Zambia, Kenya and Tanzania on both Eucalyptus and native Syzygium cordatum trees. This significantly expands the geographical distribution of these important pathogens. The studies have also shown that Chrysoporthe cubensis has recently been introduced on the continent. It is my hope that new knowledge emerging from studies in this thesis will aid in quarantine measure to control the spread of these important fungal pathogens including the new species Celoporthe dispersa.Thesis (PhD)--University of Pretoria, 2008.Microbiology and Plant PathologyPhDUnrestricte

Efficiency of natural wood extractives as wood preservatives against termite attack

Wood extractives play a major role in the protection of wood against termite and fungal attack. Wood extractives from three hard wood species of Milicia excelsa, Albizia coriaria and Markhamia lutea that are known to be very resistant against termite attack and fungal decay were studied to assess their role as wood preservatives in Uganda. Acetone, hexane and distilled water were used in the extraction of these compounds from the outer heartwood of the selected durable species. Extraction was done using a soxhlet extractor. The extractives obtained were used to treat Pinus caribaea and Antiaris toxicaria species known to be susceptible to termites and fungal attack. Treated blocks were then exposed to Macrotermes bellicosus termites in the field. It was observed that wood extracts used as preservatives improved the resistance of less durable samples to termite attack by 50% compared to the controls. It was also observed that removal of extractives decreased resistance of the durable samples. It can be concluded that wood extractives contribute greatly to the protection of less durable wood species against termite attack