Fungi associated with the die-back of Pterocarpus angolensis (kiaat) in South Africa

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. CopyrightDissertation (MSc)--University of Pretoria, 2010.Microbiology and Plant Pathologyunrestricte

Botryosphaeriaceae associated with die-back of Schizolobium parahyba trees in South Africa and Ecuador

Die-back of Schizolobium parahyba var. amazonicum is a serious problem in plantations of these trees in Ecuador. Similar symptoms have also been observed on trees of this species in various parts of South Africa. The most common fungi isolated from disease symptoms on S. parahyba var. amazonicum in both locations were species of the Botryosphaeriaceae. The aim of this study was to identify these fungi from both Ecuador and South Africa, and to test their pathogenicity in greenhouse and field trials. Isolates obtained were grouped based on culture morphology and identified using comparisons of DNA sequence data for the internal transcribed spacer (ITS) and translation elongation factor 1[alpha] (TEF-1[alpha]) gene regions. The β-tubulin-2 (BT2) locus was also sequenced for some isolates where identification was difficult. Three greenhouse trials were conducted in South Africa along with a field trial in Ecuador. Neofusicoccum parvum was obtained from trees in both areas and was the dominant taxon in South Africa. Lasiodiplodia theobromae was the dominant taxon in Ecuador, probably due to the subtropical climate in the area. Isolates of Neofusicoccum vitifusiforme (from South Africa only), Neofusicoccum umdonicola and Lasiodiplodia pseudotheobromae (from Ecuador only) were also obtained. All isolates used in the pathogenicity trials produced lesions on inoculated plants, suggesting that the Botryosphaeriaceae contribute to the die-back of S. parahyba trees. While the disease is clearly not caused by a single species of the Botryosphaeriaceae in either region, N. parvum has been introduced into at least one of the regions. This species has a broad host range and could have been introduced on other hosts.The Department of Science and Technology (DST)/National Research Foundation (NRF) Centre of Excellence in Tree Health Biotechnology (CTHB) and members of the Tree Protection Co-operative Programme (TPCP), South Africa.http://onlinelibrary.wiley.comjournal/10.1111/(ISSN)1439-03292015-10-30hj201

Invasive everywhere? Phylogeographic analysis of the globally distributed tree pathogen Lasiodiplodia theobromae

Fungi in the Botryosphaeriaceae are important plant pathogens that persist endophytically in infected plant hosts. Lasiodiplodia theobromae is a prominent species in this family that infects numerous plants in tropical and subtropical areas. We characterized a collection of 255 isolates of L. theobromae from 52 plants and from many parts of the world to determine the global genetic structure and a possible origin of the fungus using sequence data from four nuclear loci. One to two dominant haplotypes emerged across all loci, none of which could be associated with geography or host; and no other population structure or subdivision was observed. The data also did not reveal a clear region of origin of the fungus. This global collection of L. theobromae thus appears to constitute a highly connected population. The most likely explanation for this is the human-mediated movement of plant material infected by this fungus over a long period of time. These data, together with related studies on other Botryosphaeriaceae, highlight the inability of quarantine systems to reduce the spread of pathogens with a prolonged latent phase.Supplementary material. Figure S1: Maximum likelihood tree of the tef1a sequence dataset for the initial identification of isolates for inclusion in this study. Included were type and paratype strains of other Lasiodiplodia species, Figure S2: STRUCTURE output from pairwise comparisons of populations. Each plot includes the DeltaK analysis from STRUCTURE HARVESTER (top) and the corresponding barplot for the highest value of K. Pairwise comparisons as follows: (a) north America and south America, (b) north America and Africa, (c) north America and Eurasia, (d) north America and Australasia, (e) south America and Africa, (f) south America and Eurasia, (g) south America and Australasia, (h) Africa and Eurasia, (i) Africa and Australasia and (j) Eurasia and Australasia, Table S1: Polymorphic sites for the respective haplotypes for the ITS, tef1a and tub2 datasets, Table S2: Haplotype assignments for every isolate used in this study, based on the sequence datasets, Table S3: Summary of haplotypes obtained and unique haplotypes (listed in brackets) found for each locus, Table S4: Posterior probabilities (with 95% confidence intervals in parentheses) of pairwise comparisons for three scenarios to test for possible ancestry between populations done in DIYABC. In scenario 1, population 1 is ancestral to both. In scenario 2, population 2 is ancestral to both. In scenario 3, both populations diverged from an unknown source population.The Department of Science and Technology (DST)-National Research Foundation (NRF) Centre of Excellence in Tree Health Biotechnology (CTHB) and members of the Tree Protection Co-operative Programme (TPCP), South Africa.http://www.mdpi.com/journal/forestsam2017Forestry and Agricultural Biotechnology Institute (FABI)GeneticsMicrobiology and Plant PathologyPlant Production and Soil Scienc

Die-back of kiaat (Pterocarpus angolensis) in southern Africa : a cause for concern?

Pterocarpus angolensis (kiaat) is a well-known southern African tree species of commercial importance that occurs in several vegetation types in the Zambezian regional centre of endemism. The most prominent of these vegetation types are the Zambezian miombo woodland and undifferentiated woodland. A diverse range of ecosystems within these vegetation types necessitate adaptation by tree species to survive extremes of drought, temperature, altitude, soil nutrition and tolerate fire in order to compete with other plant species. There are several reports of a die-back disease of P. angolensis in Zambia, Zimbabwe and South Africa, but very little is known regarding the cause or significance of this problem. In this review, we provide details regarding the history of the disease and consider its possible causal agents. A pathology study conducted at three locations in South Africa on diseased and dying trees resulted in the collection of 199 fungal isolates; comprising saprophytic species such as Candida, Penicillium and Humicola, and potentially pathogenic species such as Lasiodiplodia theobromae, Cytospora spp. and Fusarium spp. Drought, during several years preceding disease, along with a lack of fire management may have contributed to both the present and past reports of tree die-back and death. Finally, an analysis is made of the importance of the problem and actions that might be taken to alleviate it.DST/NRF Centre of Excellence in Tree Health Biotechnology (CTHB)http://www.tandfonline.com/loi/tsfs20nf201

Confronting the constraints of morphological taxonomy in the Botryosphaeriales

Identification of fungi and the International Code of Nomenclature underpinning this process, rests strongly on the characterisation of morphological structures. Yet, the value of these characters to define species in many groups has become questionable or even superfluous. This has emerged as DNA-based techniques have increasingly revealed cryptic species and species complexes. This problem is vividly illustrated in the present study where 105 isolates of the Botryosphaeriales were recovered from both healthy and diseased woody tissues of native Acacia spp. in Namibia and South Africa. Thirteen phylogenetically distinct groups were identified based on Internal Transcribed Spacer (ITS) rDNA PCR-RFLP and translation elongation factor 1-α (TEF1-α) sequence data, two loci that are known to be reliable markers to distinguish species in the Botryosphaeriales. Four of these groups could be linked reliably to sequence data for formerly described species, including Botryosphaeria dothidea, Dothiorella dulcispinae, Lasiodiplodia pseudotheobromae and Spencermartinsia viticola. Nine groups, however, could not be linked to any other species known from culture and for which sequence data are available. These groups are, therefore, described as Aplosporella africana, A. papillata, Botryosphaeria auasmontanum, Dothiorella capri-amissi, Do. oblonga, Lasiodiplodia pyriformis, Spencermartinsia rosulata, Sphaeropsis variabilis and an undescribed Neofusicoccum sp. The species described here could not be reliably compared with the thousands of taxa described in these genera from other hosts and regions, where only morphological data are available. Such comparison would be possible only if all previously described taxa are epitypified, which is not a viable objective for the two families, Botryosphaeriaceae and Aplosporellaceae, in the Botryosphaeriales identified here. The extent of diversity of the Botryosphaeriales revealed in this and other recent studies is expected to reflect that of other undersampled regions and hosts, and illustrates the urgency to find more effective ways to describe species in this, and indeed other, groups of fungi.THRIP initiative of the Department of Trade and Industry, DST/NRF Centre of Excellence in Tree Health Biotechnology (CTHB), (DST) and National Research Foundation (NRF).http://www.persoonia.orghttp://www.ingentaconnect.com/content/nhn/pimjtm201

Overlap of latent pathogens in the Botryosphaeriaceae on a native and agricultural host

Some species of the Botryosphaeriaceae are capable of infecting a broad range of host plants. We studied the species diversity of Botryosphaeriaceae associated with marula (Sclerocarya birrea subsp. caffra, Anacardiaceae) trees in South Africa over two seasons, as well as species common to both S. birrea and adjacent mango (Mangifera indica, Anacardiaceae) trees in a subset of sites. Gene flow amongst populations of Botryosphaeriaceae shared on these tree species was tested using microsatellite markers. Twelve species were identified from S. birrea and eleven species were found on M. indica trees. From isolations done in 2006, the dominant species on S. birrea was Neofusicoccum vitifusiforme, while N. parvum was the dominant species isolated from M. indica. Neofusicoccum parvum was dominant in isolations from both hosts in 2012. Isolates of Botryosphaeria fabicerciana, Lasiodiplodia mahajangana, L. pseudotheobromae, L. theobromae, N. mediterraneum and N. umdonicola were also collected from both hosts. Population genetic analyses on isolates of N. parvum suggested that three populations were present, each comprising isolates from both hosts. There was significant gene flow between N. parvum populations on these hosts. This ability to infect multiple hosts and to migrate amongst them facilitates the establishment and spread of species and genotypes of the Botryosphaeriaceae, such as N. parvum, in new areas.Department of Science and Technology (DST)-National Research Foundation (NRF) Centre of Excellence in Tree Health Biotechnology (CTHB) and members of the Tree Protection Co-operative Programme (TPCP), South Africa.http://www.elsevier.com/locate/funbio2018-04-30hb2016Forestry and Agricultural Biotechnology Institute (FABI)Microbiology and Plant PathologyPlant Scienc

Botryosphaeriaceae associated with Pterocarpus angolensis (kiaat) in South Africa

There have been several recent reports of Pterocarpus angolensis (kiaat) trees dying in South Africa, Zambia and Zimbabwe, where this tree is used in traditional medicine and is a valuable source of timber for woodcarving and furniture. A survey of material from diseased P. angolensis trees in South Africa yielded isolates of the Botryosphaeriaceae, an important fungal family known to cause a number of tree diseases. The aim of this study was to identify these Botryosphaeriaceae and to determine their pathogenicity to P. angolensis with branch inoculations. Seven species of the Botryosphaeriaceae were identified based on a combination of morphological characteristics and sequences from the ITS and EF-1{alpha} gene regions. Four of these represent undescribed taxa for which the names Pseudofusicoccum violaceum, P. olivaceum, Diplodia alatafructa and Fusicoccum atrovirens are provided. The remaining three species collected include Lasiodiplodia theobromae, L. pseudotheobromae and L. crassispora. Inoculation trials on tree branches showed that L. pseudotheobromae and one isolate of D. alatafructa differed significantly from control inoculations. The high levels of virulence and common occurrence of L. pseudotheobromae suggest that this species could play a role in tree dieback and death.Department of Science and Technology (DST)/National Research Foundation (NRF) Centre of Excellence in Tree Health Biotechnology (CTHB), members of the Tree Protection Co-operative Program (TPCP

Botryosphaeriaceae on Syzygium cordatum across a latitudinal gradient in South Africa

The Botryosphaeriaceae is a family of endophytic fungi, many of which are latent pathogens of woody plants. Although extensively sampled in some parts of the world, little is known regarding their occurrence across different environmental conditions. This study considered the presence of the Botryosphaeriaceae on Syzygium cordatum trees across a latitudinal gradient. We examined the relative importance of different environmental factors on the presence of the Botryosphaeriaceae across this latitudinal gradient. Specifically, Botryosphaeriaceae community composition and species richness were analysed. The optimal growth temperature of the most common Botryosphaeriaceae isolates and its relation to isolate origin was also tested in culture. We identified 14 Botryosphaeriaceae species including seven each of Lasiodiplodia and Neofusicoccum species. The maximum historical temperature emerged as the environmental factor that best predicted the presence of Botryosphaeriaceae species in S. cordatum trees, specifically influencing Botryosphaeriaceae community composition. For all the Botryosphaeriaceae species studied in vitro, temperature strongly influenced mycelial growth and they all had an optimal growth temperature of 25 °C. Contrary to our hypothesis, the optimal growth temperature was not related to isolate origin. These results contribute to understanding the presence of the Botryosphaeriaceae in trees and our ability to detect these latent pathogens.The Department of Science and Innovation (DSI)-National Research Foundation (NRF) Centre of Excellence in Plant Health Biotechnology (CPHB), members of the Tree Protection Co-operative Programme (TPCP), the Claude Leon Foundation and “Juan de la Cierva Program”, Ministry of Economy, Industry and Competitiveness, Government of Spain.http://www.elsevier.com/locate/funbio2022-04-30hj2021BiochemistryForestry and Agricultural Biotechnology Institute (FABI)GeneticsMicrobiology and Plant PathologyPlant Production and Soil Scienc

Die-back of kiaat (Pterocarpus angolensis) in southern Africa : a cause for concern?

Pterocarpus angolensis (kiaat) is a well-known southern African tree species of commercial importance that occurs in several vegetation types in the Zambezian regional centre of endemism. The most prominent of these vegetation types are the Zambezian miombo woodland and undifferentiated woodland. A diverse range of ecosystems within these vegetation types necessitate adaptation by tree species to survive extremes of drought, temperature, altitude, soil nutrition and tolerate fire in order to compete with other plant species. There are several reports of a die-back disease of P. angolensis in Zambia, Zimbabwe and South Africa, but very little is known regarding the cause or significance of this problem. In this review, we provide details regarding the history of the disease and consider its possible causal agents. A pathology study conducted at three locations in South Africa on diseased and dying trees resulted in the collection of 199 fungal isolates; comprising saprophytic species such as Candida, Penicillium and Humicola, and potentially pathogenic species such as Lasiodiplodia theobromae, Cytospora spp. and Fusarium spp. Drought, during several years preceding disease, along with a lack of fire management may have contributed to both the present and past reports of tree die-back and death. Finally, an analysis is made of the importance of the problem and actions that might be taken to alleviate it.DST/NRF Centre of Excellence in Tree Health Biotechnology (CTHB)