Ceratocystis and Ophiostoma species infecting wounds on hardwood trees, with particular reference to South Africa

This thesis concerns the study of selected Ceratocystis species and Ophiostoma species infecting wounds on broad-leaved trees, particularly those occurring in Africa. However, two chapters also deal with these fungi from Australia, Norway, Sweden and Austria. The dissertation is comprised of a literature review, followed by four research chapters, addressing the occurrence of Ceratocystis spp. and Ophiostoma spp. in Africa, Australia and Norway. The first chapter of the dissertation is a review of Ceratocystis spp. and Ophiostoma spp. with particular reference to Africa, hardwood tree species and wound infections. The review highlights the importance of wood and trees, especially on the African continent, and discusses the threat of deforestation. This is despite efforts by many African countries to establish forests of non-native tree species to address the demand for wood and wood products on the continent. Reforestation is associated with increased risks of the introduction of pests and pathogens, including species of Ceratocystis and Ophiostoma. The taxonomic history of these two fungal genera is summarized, and the review further focuses on the economically important species in these genera, particularly those infecting hardwood tree species on the African continent. The lack of information regarding Ceratocystis spp. and Ophiostoma spp. on hardwood trees in Africa is thus highlighted. Furthermore, the review summarised the dispersal mechanisms of these pathogens, highlighting dispersal too and infection of wounds. Ceratocystis pirilliformis was described in 2003 and it is the only species in the Ceratocystis fimbriata species complex that has pear-shaped ascomatal bases. This fungus was first described from Australia where Eucalyptus spp. are endemic. It was later reported from South Africa on Eucalyptus grandis trees. Chapter two of this dissertation attempts to address questions regarding the geographic distribution, impact and origin of C. pirilliformis in South Africa. This was in line with the fact that it has been suggested that the fungus is likely native to Australia. To address this question, surveys were conducted in many Eucalyptus planting areas in South Africa and the genetic diversity of the fungus in the country was investigated using microsatellite markers previously developed for C. fimbriata. C. pirilliformis was found in three Eucalyptus-growing areas of South Africa, which has considerably increased the known geographic range of the fungus in South Africa. The gene diversity as well as the genotypic diversity for the fungus was found to be very low in the country and the population is apparently clonal. Results thus support the view that C. pirilliformis was accidentally introduced into South Africa. In chapter three of this dissertation, O. quercus is reported for the first time from wounds on non-native Acacia mearnsii in Uganda. In addition a new Pesotum sp., P. australi prov. nom. is described from wounds on native A. mearnsii in Australia. This fungus resembles other Pesotum anamorphs of Ophiostoma in many ways, especially species of the O. piceae complex. However, it can be distinguished from these species by many morphological traits and also based on phylogenetic inference. The closest phylogenetic neighbor of P. australi prov. nom. is O. quercus. The fact that it was isolated from A. mearnsii in Australia indicates that it is probably a native fungus in that area. In chapter four, two Ceratocystis spp. and one Ophiostoma sp. are described as new to science, from wounds on native broad-leaved tree in South Africa. Three other Ophiostomaspp. are also reported in this study. Until recently, very little research has been done with regard to Ceratocystis spp. and Ophiostoma spp. occurring on native tree species in Africa. However, results presented in this chapter strongly suggest that these fungi are common on native trees in Africa and many other species, including potential pathogens await discovery. Chapter five of the dissertation reports, for the first time, Ophiostoma catonianum, O. pluriannulatum and O. quercus from native broad-leaved trees in Norway. It also reports O. catonianum for the first time from Austria and O. quercus for the first time from Sweden. In the past, very little research has been undertaken to explore the diversity of these fungi on hardwood trees in the Nordic countries or other parts of Europe, where most research has been focused on Ceratocystis spp. and Ophiostoma spp. associated with conifer-infesting bark beetles. This chapter represents a preliminary study with important discoveries. It indicates that these fungi are common on wounds on hardwood trees in Europe and emphasizes the importance of expanding these studies in the Nordic countries, to include more hosts and geographic areas. Such studies will almost certainly reveal more species and possibly new species of Ceratocystis and Ophiostoma.Dissertation (MSc)--University of Pretoria, 2010.Microbiology and Plant PathologyUnrestricte

Ceratocystis species, including two new taxa, from Eucalyptus trees in South Africa

The ascomycete genus Ceratocystis (Microascales, Ceratocystidaceae) includes important fungal pathogens of trees, including Eucalyptus species. Ceratocystis species and their Thielaviopsis asexual states are typically associated with insects, such as nitidulid beetles, that spread them over long distances. Eucalyptus trees comprise a substantial component of the forestry industry in South Africa, however, limited information is available regarding Ceratocystis species that infect these trees. In this study, Ceratocystis species were collected from wounds on Eucalyptus trees in all the major plantation regions of South Africa, as well as from insects associated with these wounds. Both morphology and multigene DNA sequence analyses, using three nuclear loci, were used to identify the Ceratocystis species. Of the 260 isolates collected, nine Ceratocystis species, of which two were represented only by their Thielaviopsis anamorph states were identified. These species were C. eucalypticola, C. pirilliformis, C. savannae, C. oblonga, C. moniliformis, T. basicola, T. thielavioides and two Ceratocystis species that are described here as C. salinaria sp. nov. and C. decipiens sp. nov. Insects associated with these Ceratocystis species were Brachypeplus depressus (Nitidulidae), Carpophylus bisignatus, C. dimidiatus (Nitidulidae), Xyleborus affinis (Scolytidae), Litargus sp. (Mycetophagidae) and a Staphylinid (Staphylinidae) species.National Research Foundation of South Africa (NRF), the THRIP Initiative of the Department of Trade and Industry (THRIP/DST), members of the Tree Protection Cooperative Programme (TPCP) and the University of Pretoria.http://link.springer.com/journal/13313hb201

Sporendocladia bactrospora associated with wounds on native broadleaved trees in Norway and Sweden

A survey to identify ophiostomatoid fungi that infect wounds on native Norwegian and Swedish broadleaved trees was undertaken during summer 2004. A fungus resembling a species of Sporendocladia was commonly isolated from the exposed cambium and inner bark of wounds. Morphological examination and comparisons of DNA sequence data for the ITS and 5.8S regions of the rRNA gene region led to its identification as Sporendocladia bactrospora. Pathogenicity trials on young Populus tremula and Betula pubescens trees showed that S. bactrospora is capable of causing lesions on these trees. There have been few previous reports of S. bactrospora, and in most cases, these have been as saprophytes on wood. In contrast, results of this study show that it is a common inhabitant of freshly made wounds on native broadleaved trees in Scandinavia, and it appears to contribute to staining of wood.Norwegian Research Council (152266/V10)http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1439-0329hb201

A diverse assemblage of Ophiostoma species, including two new taxa on eucalypt trees in South Africa

Fungi in the Ophiostomatales include important pathogens of trees as well as agents of wood stain, reducing the economic value of timber. They rely on insects, such as bark beetles, for dispersal and are commonly associated with wounds on trees. Although Ophiostoma spp. have been reported from eucalypt wood chips in South Africa, very little is known about the diversity of the Ophiostomatales, or their insect associates, on plantation-grown Eucalyptus spp. The aim of this study was to consider the diversity and distribution of the Ophiostomatales infecting fresh wounds on Eucalyptus trees in the country. Additionally, knowledge regarding their association with nitidulid beetles, which have previously been shown to carry Ophiostoma spp., was sought. Surveys were conducted in five provinces where Eucalyptus spp. are commonly grown, and the fungi collected were identified using morphological comparisons and multigene sequence phylogenies. Of the 139 isolates collected, five Ophiostoma spp. were identified including O. quercus, O. tsotsi and O. tasmaniense. These were from cut stumps as well as from the nitidulid beetles Brachypeplus depressus and Carpophilus spp. In addition, two new taxa in the O. stenoceras–Sporothrix schenckii complex were identified from Eucalyptus trees infested by Phoracantha semipunctata. The two new taxa are described as O. candidum sp. nov., and O. fumeum sp. nov., respectively. The results of this study clearly show that the diversity and ecology of Ophiostoma spp. on Eucalyptus trees in South Africa is poorly understood and that further studies are required to determine the possible economic relevance of these fungi.The DST/NRF Center of Excellence in Tree Health Biotechnology (CTHB), National Research Foundation of South Africa (NRF), the THRIP Initiative of the Department of Trade and Industry (THRIP/DST), members of the Tree Protection Co-operative Programme (TPCP) and the University of Pretoria.http://www.springerlink.com/content/120015

Ophiostomatoid fungi and their insect associates on Eucalyptus trees in Australia and South Africa

The eucalypt plantation industry in South Africa is an important source of revenue for the country. Eucalypt trees have been planted in the country for more than 200 years, as ornamentals, sources of fuel and construction wood, and more recently also for the production of paper and rayon, amongst other uses. The planting of eucalypts in South Africa has contributed to the development of many forestry industries. It has also reduced the logging of indigenous forests. Eucalypts in South Africa are, however, affected by numerous pests and pathogens. These include native South African pests and pathogens, as well as those introduced from other countries. Of the pathogens, those commonly reffered to as pathogenic Ophiostomatoid fungi, particularly species of Ceratocystis and Ophiostoma are probably the best known. In recent years, some fungal species in the genera Ceratocystis and Ophiostoma have emerged as important threats to plantation forestry globally and it is critical to understand these fungi in order to reduce their future impact on eucalypts. In this dissertation, Ophiostomatoid fungi that infested eucalypt trees in Australia and South Africa, that were also identified from nitidulid beetles that visit these hosts, were identified using morphology and DNA sequence data. As a foundation for the studies in the dissertation chapter one provided a review of the literature pertaining to insects in the Nitidulidae and their association with fungi including Ceratocystis spp. In chapters two and three, four new taxa, C. tyalla, C. corymbiicola, O. tasmaniense, O. undulatum as well as four previously known species, C. pirilliformis, Ophiostoma quercus, O. tsotsi, Pesotum australiae were identified from eucalypts in Australia. The four new taxa were not pathogenic to E. grandis seedlings in greenhouse inoculation studies. In the last two chapters, seven Ceratocystis and five Ophiostoma spp. were identified from various Eucalyptus spp. and including some isolated from nitidulid beetles in South Africa. The Ceratocystis spp. included two new taxa (C. salinaria, C. decipiens) and five known species, C. eucalypticola, C. pirilliformis, C. moniliformis, C. oblonga, C. savannae. The Ophiostoma spp. included two new taxa of the Ophiostoma stenoceras-Sporothrix schenkii species complex (O. candidum, O. fumeum) and three known species (O. quercus, O. tsotsi, O. tasmaniense). The new taxa of Ceratocystis and Ophiostoma identified in South Africa were not pathogenic to E. grandis seedlings in a greenhouse inoculation studies. Most of the fungi identified were encountered on some nitidulid insects, and four of these fungi where found in both Australia and South Africa. This suggests an intercontinental movement of Ceratocystis and Ophiostoma, probably mediated by insects, in particular nitidulid beetles.Thesis (PhD)--University of Pretoria, 2011.Microbiology and Plant PathologyUnrestricte

Arable agriculture changes soil microbial communities in the South African Grassland Biome

7 páginas, 3 figuras, 1 tabla. -- This article is available at http://www.sajs.co.zaMany studies, mostly in temperate regions of the northern hemisphere, have demonstrated that agricultural practices affect the composition and diversity of soil microbial communities. However, very little is known about the impact of agriculture on the microbial communities in other regions of the world, most particularly on the African continent. In this study, we used MiSeq amplicon sequencing of bacterial 16S rRNA genes and fungal ITS regions to characterise microbial communities in agricultural and natural grassland soils located in the Mpumalanga Province of South Africa. Nine soil chemical parameters were also measured to evaluate the effects of edaphic factors on microbial community diversity. Bacterial and fungal communities were significantly richer and more diverse in natural grassland than in agricultural soils. Microbial taxonomic composition was also significantly different between the two habitat types. The phylum Acidobacteria was significantly more abundant in natural grassland than in agricultural soils, while Actinobacteria and the family Nectriaceae showed the opposite pattern. Soil pH and phosphorus significantly influenced bacterial communities, whereas phosphorus and calcium influenced fungal communities. These findings may be interpreted as a negative impact of land-use change on soil microbial diversity and composition.National Research Foundation (South Africa); University of PretoriaPeer reviewe

Arable agriculture changes soil microbial communities in the South African Grassland Biome

Many studies, mostly in temperate regions of the northern hemisphere, have demonstrated that agricultural practices affect the composition and diversity of soil microbial communities. However, very little is known about the impact of agriculture on the microbial communities in other regions of the world, most particularly on the African continent. In this study, we used MiSeq amplicon sequencing of bacterial 16S rRNA genes and fungal ITS regions to characterise microbial communities in agricultural and natural grassland soils located in the Mpumalanga Province of South Africa. Nine soil chemical parameters were also measured to evaluate the effects of edaphic factors on microbial community diversity. Bacterial and fungal communities were significantly richer and more diverse in natural grassland than in agricultural soils. Microbial taxonomic composition was also significantly different between the two habitat types. The phylum Acidobacteria was significantly more abundant in natural grassland than in agricultural soils, while Actinobacteria and the family Nectriaceae showed the opposite pattern. Soil pH and phosphorus significantly influenced bacterial communities, whereas phosphorus and calcium influenced fungal communities. These findings may be interpreted as a negative impact of land-use change on soil microbial diversity and composition. SIGNIFICANCE: • This report is the first of the effect of land-use changes on the diversity of the soil microbial communities in African grassland soils. • Land-use changes influence the diversity and structure of soil microbial communities in the Grassland Biome of South Africa. • This study serves as a baseline for future studies on South African soil microbial diversity.National Research Foundation (South Africa); University of Pretoriahttp://www.sajs.co.zaam2018Genetic

Arable agriculture changes soil microbial communities in the South African Grassland Biome

Many studies, mostly in temperate regions of the northern hemisphere, have demonstrated that agricultural practices affect the composition and diversity of soil microbial communities. However, very little is known about the impact of agriculture on the microbial communities in other regions of the world, most particularly on the African continent. In this study, we used MiSeq amplicon sequencing of bacterial 16S rRNA genes and fungal ITS regions to characterise microbial communities in agricultural and natural grassland soils located in the Mpumalanga Province of South Africa. Nine soil chemical parameters were also measured to evaluate the effects of edaphic factors on microbial community diversity. Bacterial and fungal communities were significantly richer and more diverse in natural grassland than in agricultural soils. Microbial taxonomic composition was also significantly different between the two habitat types. The phylum Acidobacteria was significantly more abundant in natural grassland than in agricultural soils, while Actinobacteria and the family Nectriaceae showed the opposite pattern. Soil pH and phosphorus significantly influenced bacterial communities, whereas phosphorus and calcium influenced fungal communities. These findings may be interpreted as a negative impact of land-use change on soil microbial diversity and composition. Significance: This report is the first of the effect of land-use changes on the diversity of the soil microbial communities in African grassland soils. Land-use changes influence the diversity and structure of soil microbial communities in the Grassland Biome of South Africa. This study serves as a baseline for future studies on South African soil microbial diversit

Distribution and population diversity of Ceratocystis pirilliformis in South Africa

Ceratocystis pirilliformis was first isolated from wounds on Eucalyptus nitens in Australia and subsequently found in a similar niche on E. grandis in South Africa. Artificial inoculation studies under field conditions in South Africa resulted in bark lesions and sapstain, suggesting that the fungus is a pathogen of potential importance to forestry in South Africa. Because Eucalyptus spp. are native to Australia and C. pirilliformis was first found there in the absence of disease it has been assumed that the fungus is native to Australia. The aim of this study was to expand the base of knowledge regarding the distribution and population diversity of C. pirilliformis in South Africa. Wounds were examined on Eucalyptus spp. growing in seven of the most important forestry areas in South Africa. PCR-based microsatellite markers, developed for the closely related tree pathogen C. fimbriata sensu lato were used to assess the diversity of the isolates collected. Ceratocystis pirilliformis was found in four out of seven areas surveyed, substantially expanding its known distribution in South Africa. Of the 27 available microsatellite markers, 18 amplified the desired loci of C. pirilliformis and of these, seven were polymorphic. Measures of genetic diversity based on gene diversity, genotypic diversity as well as allelic richness indicated that the isolates from South Africa has a low level of genetic diversity and that the fungus is most likely not native to the country. Inclusion of available Australian isolates showed much higher diversity for C. pirilliformis in that country

Ceratocystis species, including two new species associated with nitidulid beetles, on eucalypts in Australia

The genus Ceratocystis includes important fungal pathogens of trees, including Eucalyptus spp. Ironically, very little is known regarding the diversity or biology of Ceratocystis species on Eucalyptus species in Australia, where most of these trees are native. The aim of this study was to survey for Ceratocystis spp., and their possible insect associates on eucalypts in Australia and thus, to establish a foundation of knowledge regarding these fungi on the continent. Collections were made in three states of Australia from wounds on trees, as well as from nitidulid beetles associated with these wounds. Ceratocystis spp. were identified based on morphology and multigene sequence comparisons. Of the 54 isolates obtained, two previously unknown species of Ceratocystis were found and these are described here as C. corymbiicola sp. nov. and C. tyalla sp. nov. Furthermore, the distribution of C. pirilliformis is expanded to include Eucalyptus spp. in Tasmania.The DST/NRF Center of Excellence in Tree Health Biotechnology (CTHB), National Research Foundation of South Africa (NRF), the THRIP Initiative of the Department of Trade and Industry (THRIP/DST), members of the Tree Protection Co-operative Programme (TPCP) and the University of Pretoria.http://www.springerlink.com/content/100234/nf201