Browsing by Author "Wingfield, Michael J."
Now showing 1 - 12 of 12
Results Per Page
- ItemEcological disequilibrium drives insect pest and pathogen accumulation in non-native trees(Oxford University Press on behalf of the Annals of Botany Company, 2017) Crous, Casparus J.; Burgess, Treena I.; Le Roux, Johannes J.; Richardson, David M.; Slippers, Bernard; Wingfield, Michael J.Non-native trees have become dominant components of many landscapes, including urban ecosystems, commercial forestry plantations, fruit orchards and as invasives in natural ecosystems. Often, these trees have been separated from their natural enemies (i.e. insects and pathogens) leading to ecological disequilibrium, that is, the immediate breakdown of historically co-evolved interactions once introduced into novel environments. Long-established, non-native tree plantations provide useful experiments to explore the dimensions of such ecological disequilibria. We quantify the status quo of non-native insect pests and pathogens catching up with their tree hosts (planted Acacia, Eucalyptus and Pinus species) in South Africa, and examine which native South African enemy species utilize these trees as hosts. Interestingly, pines, with no confamilial relatives in South Africa and the longest residence time (almost two centuries), have acquired only one highly polyphagous native pathogen. This is in contrast to acacias and eucalypts, both with many native and confamilial relatives in South Africa that have acquired more native pathogens. These patterns support the known role of phylogenetic relatedness of non-native and native floras in influencing the likelihood of pathogen shifts between them. This relationship, however, does not seem to hold for native insects. Native insects appear far more likely to expand their feeding habits onto non-native tree hosts than are native pathogens, although they are generally less damaging. The ecological disequilibrium conditions of non-native trees are deeply rooted in the eco-evolutionary experience of the host plant, co-evolved natural enemies and native organisms from the introduced range. We should expect considerable spatial and temporal variation in ecological disequilibrium conditions among non-native taxa, which can be significantly influenced by biosecurity and management practices.
- ItemEvolutionary dynamics of tree invasions : complementing the unified framework for biological invasions(Oxford University Press on behalf of the Annals of Botany Company, 2017) Zenni, Rafael D.; Dickie, Ian A.; Wingfield, Michael J.; Hirsch, Heidi; Crous, Casparus J.; Meyerson, Laura A.; Burgess, Treena I.; Zimmermann, Thalita G.; Klock, Metha M.; Siemann, Evan; Erfmeier, Alexandra; Aragon, Roxana; Montti, Lia; Le Roux, Johannes J.Evolutionary processes greatly impact the outcomes of biological invasions. An extensive body of research suggests that invasive populations often undergo phenotypic and ecological divergence from their native sources. Evolution also operates at different and distinct stages during the invasion process. Thus, it is important to incorporate evolutionary change into frameworks of biological invasions because it allows us to conceptualize how these processes may facilitate or hinder invasion success. Here, we review such processes, with an emphasis on tree invasions, and place them in the context of the unified framework for biological invasions. The processes and mechanisms described are pre-introduction evolutionary history, sampling effect, founder effect, genotype-by-environment interactions, admixture, hybridization, polyploidization, rapid evolution, epigenetics and second-genomes. For the last, we propose that co-evolved symbionts, both beneficial and harmful, which are closely physiologically associated with invasive species, contain critical genetic traits that affect the evolutionary dynamics of biological invasions. By understanding the mechanisms underlying invasion success, researchers will be better equipped to predict, understand and manage biological invasions.
- ItemGenome sequences of Knoxdaviesia capensis and K. proteae (Fungi: Ascomycota) from Protea trees in South Africa(BioMed Central, 2016) Aylward, Janneke; Steenkamp, Emma T.; Dreyer, Leanne L.; Roets, Francois; Wingfield, Brenda D.; Wingfield, Michael J.Two closely related ophiostomatoid fungi, Knoxdaviesia capensis and K. proteae, inhabit the fruiting structures of certain Protea species indigenous to southern Africa. Although K. capensis occurs in several Protea hosts, K. proteae is confined to P. repens. In this study, the genomes of K. capensis CBS139037 and K. proteae CBS140089 are determined. The genome of K. capensis consists of 35,537,816 bp assembled into 29 scaffolds and 7940 predicted protein-coding genes of which 6192 (77.98 %) could be functionally classified. K. proteae has a similar genome size of 35,489,142 bp that is comprised of 133 scaffolds. A total of 8173 protein-coding genes were predicted for K. proteae and 6093 (74.55 %) of these have functional annotations. The GC-content of both genomes is 52.8 %.
- ItemIMA Genome - F13 : Draft genome sequences of Ambrosiella cleistominuta, Cercospora brassicicola, C. citrullina, Physcia stellaris, and Teratosphaeria pseudoeucalypti(BMC (part of Springer Nature), 2020-09-24) Wilken, P. Markus; Aylward, Janneke; Chand, Ramesh; Grewe, Felix; Lane, Frances A.; Sinha, Shagun; Ametrano, Claudio; Distefano, Isabel; Divakar, Pradeep K.; Duong, Tuan A.; Huhndorf, Sabine; Kharwar, Ravindra N.; Lumbsch, P. Markus; Navathe, Sudhir; Pérez, Carlos A.; Ramírez-Berrutti, Nazaret; Sharma, Rohit; Sun, Yukun; Wingfield, Brenda D.; Wingfield, Michael J.Draft genomes of the fungal species Ambrosiella cleistominuta, Cercospora brassicicola, C. citrullina, Physcia stellaris, and Teratosphaeria pseudoeucalypti are presented. Physcia stellaris is an important lichen forming fungus and Ambrosiella cleistominuta is an ambrosia beetle symbiont. Cercospora brassicicola and C. citrullina are agriculturally relevant plant pathogens that cause leaf-spots in brassicaceous vegetables and cucurbits respectively. Teratosphaeria pseudoeucalypti causes severe leaf blight and defoliation of Eucalyptus trees. These genomes provide a valuable resource for understanding the molecular processes in these economically important fungi.
- ItemIMA Genome-F 11: Draft genome sequences of Fusarium xylarioides, Teratosphaeria gauchensis and T. zuluensis and genome annotation for Ceratocystis fimbriata(BMC (part of Springer Nature), 2019-09-13) Wingfield, Brenda D.; Fourie, Arista; Simpson, Melissa C.; Bushula-Njah, Vuyiswa S.; Aylward, Janneke; Barnes, Irene; Coetzee, Martin P. A.; Dreyer, Leanne L.; Duong, Tuan A.; Geiser, David M.; Roets, Francois; Steenkamp, E. T.; Van Der Nest, Magriet A.; van Heerden, Carel J.; Wingfield, Michael J.ENGLISH ABSTRACT: Draft genomes of the fungal species Fusarium xylarioides, Teratosphaeria gauchensis and T. zuluensis are presented. In addition an annotation of the genome of Ceratocystis fimbriata is presented. Overall these genomes provide a valuable resource for understanding the molecular processes underlying pathogenicity and potential management strategies of these economically important fungi.
- ItemKnoxdaviesia proteae is not the only Knoxdaviesia-symbiont of Protea repens(International Mycological Association, 2015-11-10) Aylward, Janneke; Dreyer, Leanne L.; Steenkamp, Emma T.; Wingfield, Michael J.; Roets, FrancoisTwo polyphyletic genera of ophiostomatoid fungi are symbionts of Proteaceae in southern Africa. One of these, Knoxdaviesia, includes two closely related species, K. proteae and K. capensis, that have overlapping geographical distributions, but are not known to share Protea host species. Knoxdaviesia capensis appears to be a generalist that occupies numerous hosts, but has never been found in P. repens, the only known host of K. proteae. In this study, extensive collections were made from P. repens and isolates were identified using DNA sequence comparisons. This led to the surprising discovery of K. capensis from P. repens for the first time. The fungus was encountered at a low frequency, suggesting that P. repens is not its preferred host, which may explain why it has not previously been found on this plant. The basis for the specialisation of K. proteae and K. capensis on different Protea species remains unknown.
- ItemLessons from a major pest invasion : the polyphagous shot hole borer in South Africa(ASSAf, 2020-11-26) Paap, Trudy; Wingfield, Michael J.; De Beer, Z. Wilhelm; Roets, FrancoisThe arrival and establishment of invasive forest pests can cause devastating environmental damage and great economic impact. For example, the cost over the past decade of dealing with the arrival of a single invasive beetle in the USA, the emerald ash borer (Agrilus planipennis), is estimated at more than USD10 billion.1 Originating from Asia, this beetle has killed hundreds of millions of native ash trees since it became established in the USA. However, this beetle is but one of hundreds of invasive insect pests that impact forests in the USA, and that contribute to a global tree health crisis caused by invasive insects and pathogenic microorganisms.2-4 South Africa is no different from other countries and is experiencing an increasing rate of introductions of damaging forest pests.5,6 These invasions are largely unintentional and are a by-product of globalisation and increasing global trade.7,8 The movement of living plants and plant products, including untreated wood packaging materials (i.e. pallets, dunnage and crating), is known to be a major pathway for these pests.9,10 For clarification, in this commentary we use the terms ‘insect’ and ‘pathogen’ to distinguish between the two types of organisms, although we also use the general term ‘pest’ to refer to both groups. The term ‘invasive pest’ is used for introduced species that, in addition to maintaining a self-sustaining population, show evidence of spread and impact.
- ItemNine draft genome sequences of Claviceps purpurea s.lat., including C. arundinis, C. humidiphila, and C. cf. spartinae, pseudomolecules for the pitch canker pathogen Fusarium circinatum, draft genome of Davidsoniella eucalypti, Grosmannia galeiformis, Quambalaria eucalypti, and Teratosphaeria destructans(International Mycological Association, 2018-12-01) Wingfield, Brenda D.; Liu, Miao; Nguyen, Hai D. T.; Lane, Frances A.; Morgan, Seamus W.; De Vos, Lieschen; Wilken, P. M.; Duong, Tuan A.; Aylward, Janneke; Coetzee, Martin P. A.; Dadej, Kasia; De Beer, Z. W.; Findlay, Wendy; Havenga, Minette; Kolarik, Miroslav; Menzies, Jim G.; Naidoo, Kershney; Pochopski, Olivia; Shoukouhi, Parivash; Santana, Quentin C.; Seifert, Keith A.; Soal, Nicole; Steenkamp, Emma T.; Tatham, Catherine T.; Van Der Nest, Margriet A.; Wingfield, Michael J.This genome announcement includes draft genomes from Claviceps purpurea s.lat., including C. arundinis, C. humidiphila and C. cf. spartinae. The draft genomes of Davidsoniella eucalypti, Quambalaria eucalypti and Teratosphaeria destructans, all three important eucalyptus pathogens, are presented. The insect associate Grosmannia galeiformis is also described. The pine pathogen genome of Fusarium circinatum has been assembled into pseudomolecules, based on additional sequence data and by harnessing the known synteny within the Fusarium fujikuroi species complex. This new assembly of the F. circinatum genome provides 12 pseudomolecules that correspond to the haploid chromosome number of F. circinatum. These are comparable to other chromosomal assemblies within the FFSC and will enable more robust genomic comparisons within this species complex.
- ItemPanmixia defines the genetic diversity of a unique arthropod-dispersed fungus specific to Protea flowers(Wiley Open Access, 2014-09) Aylward, Janneke; Dreyer, Leanne L.; Steenkamp, Emma T.; Wingfield, Michael J.; Roets, FrancoisKnoxdaviesia proteae, a fungus specific to the floral structures of the iconic Cape Floral Kingdom plant, Protea repens, is dispersed by mites phoretic on beetles that pollinate these flowers. Although the vectors of K. proteae have been identified, little is known regarding its patterns of distribution. Seed bearing infructescences of P. repens were sampled from current and previous flowering seasons, from which K. proteae individuals were isolated and cultured. The genotypes of K. proteae isolates were determined using 12 microsatellite markers specific to this species. Genetic diversity indices showed a high level of similarity between K. proteae isolates from the two different infructescence age classes. The heterozygosity of the population was high (0.74 +- 0.04), and exceptional genotypic diversity was encountered (^G = 97.87%). Population differentiation was negligible, owing to the numerous migrants between the infructescence age classes (Nm = 47.83) and between P. repens trees (Nm = 2.96). Parsimony analysis revealed interconnected genotypes, indicative of recombination and homoplasies, and the index of linkage disequilibrium confirmed that outcrossing is prevalent in K. proteae (rd = 0.0067; P = 0.132). The high diversity and panmixia in this population is likely a result of regular gene flow and an outcrossing reproductive strategy. The lack of genetic cohesion between individuals from a single P. repens tree suggests that K. proteae dispersal does not primarily occur over short distances via mites as hypothesized, but rather that longdistance dispersal by beetles plays an important part in the biology of these intriguing fungi.
- ItemA plant pathology perspective of fungal genome sequencing(International Mycological Association, 2017) Aylward, Janneke; Steenkamp, Emma T.; Dreyer, Leanne L.; Roets, Francois; Wingfield, Brenda D.; Wingfield, Michael J.The majority of plant pathogens are fungi and many of these adversely affect food security. This minireview aims to provide an analysis of the plant pathogenic fungi for which genome sequences are publically available, to assess their general genome characteristics, and to consider how genomics has impacted plant pathology. A list of sequenced fungal species was assembled, the taxonomy of all species verified, and the potential reason for sequencing each of the species considered. The genomes of 1090 fungal species are currently (October 2016) in the public domain and this number is rapidly rising. Pathogenic species comprised the largest category (35.5 %) and, amongst these, plant pathogens are predominant. Of the 191 plant pathogenic fungal species with available genomes, 61.3 % cause diseases on food crops, more than half of which are staple crops. The genomes of plant pathogens are slightly larger than those of other fungal species sequenced to date and they contain fewer coding sequences in relation to their genome size. Both of these factors can be attributed to the expansion of repeat elements. Sequenced genomes of plant pathogens provide blueprints from which potential virulence factors were identified and from which genes associated with different pathogenic strategies could be predicted. Genome sequences have also made it possible to evaluate adaptability of pathogen genomes and genomic regions that experience selection pressures. Some genomic patterns, however, remain poorly understood and plant pathogen genomes alone are not sufficient to unravel complex pathogen-host interactions. Genomes, therefore, cannot replace experimental studies that can be complex and tedious. Ultimately, the most promising application lies in using fungal plant pathogen genomics to inform disease management and risk assessment strategies. This will ultimately minimize the risks of future disease outbreaks and assist in preparation for emerging pathogen outbreaks.
- ItemScientists’ warning on invasive alien species(Wiley, 2019) Pysek, Petr; Hulme, Philip E.; Simberloff, Dan; Bacher, Sven; Blackburn, Tim M.; Carlton, James T.; Dawson, Wayne; Essl, Franz; Foxcroft, Llewellyn C.; Genovesi, Piero; Jeschke, Jonathan M.; Kühn, Ingolf; Liebhold, Andrew M.; Mandrak, Nicholas E.; Meyerson, Laura A.; Pauchard, Aníbal; Pergl, Jan; Roy, Helen E.; Seebens, Hanno; Van Kleunen, Mark; Vila, Montserrat; Wingfield, Michael J.; Richardson, David M.Biological invasions are a global consequence of an increasingly connected world and the rise in human population size. The numbers of invasive alien species – the subset of alien species that spread widely in areas where they are not native, affecting the environment or human livelihoods – are increasing. Synergies with other global changes are exacerbating current invasions and facilitating new ones, thereby escalating the extent and impacts of invaders. Invasions have complex and often immense long-term direct and indirect impacts. In many cases, such impacts become apparent or problematic only when invaders are well established and have large ranges. Invasive alien species break down biogeographic realms, affect native species richness and abundance, increase the risk of native species extinction, affect the genetic composition of native populations, change native animal behaviour, alter phylogenetic diversity across communities, and modify trophic networks. Many invasive alien species also change ecosystem functioning and the delivery of ecosystem services by altering nutrient and contaminant cycling, hydrology, habitat structure, and disturbance regimes. These biodiversity and ecosystem impacts are accelerating and will increase further in the future. Scientific evidence has identified policy strategies to reduce future invasions, but these strategies are often insufficiently implemented. For some nations, notably Australia and New Zealand, biosecurity has become a national priority. There have been long-term successes, such as eradication of rats and cats on increasingly large islands and biological control of weeds across continental areas. However, in many countries, invasions receive little attention. Improved international cooperation is crucial to reduce the impacts of invasive alien species on biodiversity, ecosystem services, and human livelihoods. Countries can strengthen their biosecurity regulations to implement and enforce more effective management strategies that should also address other global changes that interact with invasions.
- ItemTeratosphaeria stem canker of Eucalyptus : two pathogens, one devastating disease(British Society for Plant Pathology, 2018) Aylward, Janneke; Roets, Francois; Dreyer, Leanne L.; Wingfield, Michael J.Background: Teratosphaeria gauchensis and T. zuluensis are closely related fungi that cause Teratosphaeria (previously Coniothyrium) stem canker disease on Eucalyptus species propagated in plantations for commercial purposes. This disease is present in many countries in which Eucalyptus trees are planted, and continues to spread with the international trade of infected plant germplasm. Taxonomy: Fungi, Ascomycota, Pezizomycotina, Dothideomycetes, Dothideomycetidae, Capnodiales, Teratosphaeriaceae, Teratosphaeria. Identification: The causal agents form dark masses of pycnidia that are visible on the surface of distinct stem cankers that typically form on young green stem tissues. Accurate diagnosis of the causal agents requires DNA sequence data. Host range: Nine species of Eucalyptus are known to be affected. Of these, E. grandis and its hybrids, which include some of the most important planting stock globally, appear to be particularly vulnerable. Disease symptoms: Small necrotic lesions develop on young green stem tissue. These lesions coalesce to form large cankers that exude gum. Epicormic shoots develop below the girdling canker and, in severe cases, trees die.