Search

Teratosphaeria destructans is one of the most aggressive foliar pathogens of Eucalyptus. The biological factors underpinning T. destructans infections, which include shoot and leaf blight on young trees, have never been interrogated. Thus, the means by which the pathogen modifies its host environment to overcome host defences remain unknown. By applying transcriptome sequencing, the aim of this study was to compare gene expression in a South African isolate of T. destructans grown on nitrogen-deficient and complete media. This made it possible to identify upregulated genes in a nitrogen-starved environment, often linked to the pathogenicity of the fungus. The results support the hypothesis that nitrogen starvation in T. destructans likely mirrors an in planta genetic response. This is because 45% of genes that were highly upregulated under nitrogen starvation have previously been reported to be associated with infection in other pathogen systems. These included several CAZymes, fungal effector proteins, peptidases, kinases, toxins, lipases and proteins associated with detoxification of toxic compounds. Twenty-five secondary metabolites were identified and expressed in both nitrogen-deficient and complete conditions. Additionally, the most highly expressed genes in both growth conditions had pathogenicity-related functions. This study highlights the large number of expressed genes associated with pathogenicity and overcoming plant defences. As such, the generated baseline knowledge regarding pathogenicity and aggressiveness in T. destructans is a valuable reference for future in planta work. [ABSTRACT FROM AUTHOR]

The aggressive Eucalyptus leaf pathogen, Teratosphaeria destructans, causes widespread damage in tropical and subtropical Eucalyptus‐growing regions of Indonesia, China, Thailand, East Timor, Vietnam, Lao, and South Africa. Little is known regarding the origin, pathways of dispersal, or reproductive biology of this pathogen. The aim of this study was to investigate the genetic structure of a global collection of T. destructans isolates. This was achieved by developing and using polymorphic microsatellite markers. Low genotypic diversity and a limited number of private alleles were found in all investigated populations, with the highest maximum diversity of 10.7% in isolates from South Sumatra. This supports the hypothesis that T. destructans was introduced to these regions. High levels of clonality were common in all populations, especially in isolates sampled from the recent disease outbreak in South Africa, which were all identical. The global collection of isolates grouped into three distinct clusters, corresponding largely to their sampled regions. Low levels of genotypic diversity, high levels of clonality, and strong geographic structure suggest independent introductions into all the sampled areas from an unknown source. The results imply that strict biosecurity measures are needed to avoid introductions of additional genotypes in these areas. [ABSTRACT FROM AUTHOR]

Climate changes, exemplified by increased temperatures and CO2 concentration, pose a global threat to forest health. Of particular concern are pests and pathogens, with a warming climate altering their distributions and evolutionary capacity, while impairing the ability of some plants to respond to infections. Progress in understanding and mitigating such effects is currently hindered by a lack of empirical research. Norway spruce (Picea abies) is one of the most economically important tree species in northern Europe, and is considered highly vulnerable to changes in climate. It is commonly infected by the fungus Endoconidiophora polonica, and we hypothesized that damage caused to trees will increase under future climate change predictions. To test this hypothesis an in vivo greenhouse experiment was conducted to evaluate the effects of a changed growing environment on E. polonica infected Norway spruce seedlings, comparing ambient conditions to predicted temperatures and CO2 levels in Finland for the years 2030 and 2100. In total, 450 seedlings were randomized amongst the three treatments, with 25 seedlings from each allocated to inoculation with one of five different fungal strains or mock-inoculation. Seedlings were monitored throughout the thermal growing season for mortality, and lesion length and depth indices were measured at the experiment conclusion. Disease severity (mortality and lesions) was consistently greater in fungal-inoculated than mock-inoculated seedlings. However, substantial differences were observed among fungal strains in response to climate scenarios. For example, although overall seedling mortality was highest under the most distant (and severe) climate change expectations, of the two fungal strains with the highest mortality counts (referred to as F4 and F5), one produced greater mortality under the 2030 and 2100 scenarios than ambient conditions, whereas climate scenario had no effect on the other. This study contributes to a limited body of empirical research on the effects of projected climate changes on forestry pathosystems, and is the first to investigate interactions between Norway spruce and E. polonica. The results indicate the potential for future climate changes to alter the impact of forest pathogens with implications for productivity, while highlighting the need for a strain-specific level of understanding of the disease agents. [ABSTRACT FROM AUTHOR]

Ralstonia solanacearum and R. pseudosolanacearum are well known primary pathogens of herbaceous crops. Reports of wilt caused by these pathogens in tree species are limited other than on Eucalyptus species. Despite the widespread occurrence of so-called bacterial wilt on eucalypts in tropical and sub-tropical parts of Africa, Asia, and the Americas, there remain many contradictions relating to the disease. Our field observations over many years in most regions where the disease occurs on Eucalyptus show that it is always associated with trees that have been subjected to severe stress. The disease is typically diagnosed by immersing cut stems in water and observing bacterial streaming, but the identity of the bacteria within this suspension is seldom considered. To add to the confusion, pathogenicity tests on susceptible species or clones are rarely successful. When they do work, they are on small plants in greenhouse trials. It has become all to easy to attribute Eucalyptus death exclusively to Ralstonia infection. Our data strongly suggest that Ralstonia species and probably other bacteria are latent colonists commonly occurring in healthy and particularly clonally propagated eucalypts. The onset of stress factors provide the bacteria with an opportunity to develop. We believe that the resulting stress weakens the defense systems of the trees allowing Ralstonia and bacterial endophytes to proliferate. Overall our research suggests that R. solanacearum and R. pseudosolanacearum are not primary pathogens of Eucalyptus. Short of clear evidence that they are primary pathogens of Eucalyptus it is inappropriate to attribute this disease solely to infection by Ralstonia species. [ABSTRACT FROM AUTHOR]

In the mid-1970s, Mozambique embarked on several forestry projects to promote and establish large plantation areas with eucalypt trees. The planted species includedCorymbia citriodora,Eucalyptus camaldulensis,E. salignaandE. tereticornis. Similar to other regions of the world, pests and pathogens pose a significant threat to eucalypt plantations in Mozambique, but little is known regarding the diseases of trees in the country. The aim of this study was to provide the first detailed consideration of the possible disease problems affecting plantation- grown eucalypt species in the central and northern provinces of Mozambique. Isolates of fungal pathogens were obtained from material displaying disease symptoms collected during two field surveys conducted in 2010 and 2011. Representative fungal isolates were identified using DNA sequence data. Stem canker diseases caused by fungi in the Botryosphaeriaceae, Cryphonectriaceae and Teratosphaeriaceae, as well as leaf spots caused by species ofCalonectria,Pilidiella,PilidiumandPhakopsora myrtacearumwere commonly encountered. Their relative importance to the future of planation forestry in Mozambique is discussed. [ABSTRACT FROM PUBLISHER]

Abstract: Dothistroma septosporum is a haploid fungal pathogen that causes a serious needle blight disease of pines, particularly as an invasive alien species on Pinus radiata in the Southern Hemisphere. During the course of the last two decades, the pathogen has also incited unexpected epidemics on native and non‐native pine hosts in the Northern Hemisphere. Although the biology and ecology of the pathogen has been well documented, there is a distinct lack of knowledge regarding its movement or genetic diversity in many of the countries where it is found. In this study we determined the global population diversity and structure of 458 isolates of D. septosporum from 14 countries on six continents using microsatellite markers. Populations of the pathogen in the Northern Hemisphere, where pines are native, displayed high genetic diversities and included both mating types. Most of the populations from Europe showed evidence for random mating, little population differentiation and gene flow between countries. Populations in North America (USA) and Asia (Bhutan) were genetically distinct but migration between these continents and Europe was evident. In the Southern Hemisphere, the population structure and diversity of D. septosporum reflected the anthropogenic history of the introduction and establishment of plantation forestry, particularly with Pinus radiata. Three introductory lineages in the Southern Hemisphere were observed. Countries in Africa, that have had the longest history of pine introductions, displayed the greatest diversity in the pathogen population, indicating multiple introductions. More recent introductions have occurred separately in South America and Australasia where the pathogen population is currently reproducing clonally due to the presence of only one mating type. [ABSTRACT FROM AUTHOR]

Fusarium circinatumis an important fungal pathogen ofPinusspecies. In South Africa, it is the most significant pathogen ofPinus patulaseedlings in forestry nurseries where it presents a substantial constraint to productivity and can continue to cause mortality in-field for up to two years after establishment. This study describes the results from two trials whereP. patulaseedlings were inoculated withF. circinatumto determine the impact of the pathogen on nursery and field performance. Seedlings were also subjected to water stress treatments to ascertain whether this would trigger the onset of disease symptoms. Inoculum load and timing of inoculation had significant effects on seedling survival in both the nursery and field. High inoculum concentrations caused greater levels of mortality and, where seedlings were inoculated at a young age, they showed higher levels of susceptibility toF. circinatum. Temporary water-stress in the nursery produced smaller plants and improved in-field survival, but this treatment did not trigger higher mortality in inoculated treatments. On the other hand, transplant stress was a major contributor to the higher levels of mortality observed in inoculated treatments. Overall, these studies confirmed that infection in the nursery leads to the disease problems observed during early plant establishment in the field. [ABSTRACT FROM AUTHOR]

The pitch canker pathogen,Fusarium circinatum, has major impacts on production in pine nurseries and plantations in South Africa. Thus far, efforts to reduce local spread have focused on rouging of infected pines and sanitation to eliminate local sources of inoculum. Although the host range ofF. circinatumwas thought to be limited to pines and Douglas-fir, recent studies in California indicate that this fungus is capable of infecting grasses as a symptomless endophyte. Consequently, it is possible that grasses represent a reservoir of inoculum that influences the occurrence of disease in South African pine nurseries and plantations. The objectives of this study were to survey a wide range of grass species in both nurseries and plantations in South Africa for the presence ofF. circinatum. In all, 22 species of grass were sampled at a nursery in Mpumulanga and in a plantation on the Western Cape. Isolates obtained from grasses were identified based on morphological criteria and DNA sequence data.Fusarium circinatumwas recovered from vegetative tissues of four grass species includingBriza maxima, Ehrharta erectavar.erecta, Pentameris pallidaand one species that could not be identified. All isolates were pathogenic to pines and comparable in virulence to a knownF. circinatumisolate that was included as a positive control. These studies indicate that grasses may constitute inoculum reservoirs that could facilitate persistence and dissemination of the pathogen in nurseries, and provide a means for the pathogen to move between widely separated pine stands, where grass hosts occur in intervening areas. [ABSTRACT FROM AUTHOR]

Since the first appearance ofFusarium circinatumin South Africa in 1990, foresters have been challenged with poor field survival ofPinus patulaseedlings at establishment. One of the best long-term solutions is to improve the genetic tolerance ofP. patulato infection by the pathogen. Currently, large numbers of families are routinely screened for their tolerance toF. circinatumby infecting open-pollinated seedlings from orchard clones in a greenhouse and assessing lesion development. In this study, nine-year-oldP. patulatrees from 96 families were inoculated withF. circinatumin the field. Their levels of tolerance were assessed and compared to those observed in seedlings originating from seed harvested from the same trees. The field results were also compared with those from previous greenhouse screening trials where seedlings from a number of the same families had been inoculated withF. circinatum. The results showed that there was a strong phenotypic (r= 0.71) and genetic (rg= 0.94) correlation in the performance of the families common in both the greenhouse studies. A comparison of the tolerance of the families, screened as both seedlings and as trees, was also meaningful (r= 0.40). Furthermore, the seedlings raised from seeds collected from the infectedP. patulatrees, that ranked more tolerant than the mean of theP. elliottiitrees, were similar in tolerance toP. elliottiiseedlings in the greenhouse trial. Our results indicate that utilising seedlings from clones known to be tolerant should improve the tolerance of mature trees to infection byF. circinatum. [ABSTRACT FROM AUTHOR]

Abstract: The Cryphonectriaceae includes important tree pathogens, especially on the Myrtales. During a routine disease survey in the Western Cape Province of South Africa, a fungus resembling the Eucalyptus pathogen Holocryphia eucalypti was observed on native Metrosideros angustifolia (Myrtales). The aims of this study were to identify the fungus and to expand surveys for fungi in the Cryphonectriaceae on M. angustifolia. Fungi were identified based on DNA sequence comparisons and morphological features, and their pathogenicity was tested on M. angustifolia under field conditions. Based on morphology and multigene phylogenetic analyses of DNA sequence data from six gene regions, we describe a new genus including a single species and three new species of Holocryphia (Cryphonectriaceae) from M. angustifolia. These fungi are provided with the names Diversimorbus metrosiderotis gen. et sp. nov., Holocryphia capensis sp. nov., Holocryphia gleniana sp. nov., and Holocryphia mzansi sp. nov. We also revise H. eucalypti, the type of the genus, to include only isolates from Eucalyptus in South Africa. Research results indicated that H. mzansi may undergo host shifts between different tree genera in the Myrtaceae. Inoculation tests showed that isolates of all the newly described species can cause lesions on the branches of M. angustifolia, indicating that they are all pathogens of this tree. [Copyright &y& Elsevier]

Human-associated introduction of pathogens and consequent invasions is very evident in areas where no related organisms existed before. In areas where related but distinct populations or closely related cryptic species already exist, the invasion process is much harder to unravel. In this study, the population structure of the Eucalyptus leaf pathogen Teratosphaeria nubilosa was studied within its native range in Australia, including both commercial plantations and native forests. A collection of 521 isolates from across its distribution was characterized using eight microsatellite loci, resulting in 112 multilocus haplotypes (MLHs). Multivariate and Bayesian analyses of the population conducted in structure revealed three genetically isolated groups (A, B and C), with no evidence for recombination or hybridization among groups, even when they co-occur in the same plantation. DNA sequence data of the ITS ( n = 32), β-tubulin ( n = 32) and 27 anonymous loci ( n = 16) were consistent with microsatellite data in suggesting that T. nubilosa should be considered as a species complex. Patterns of genetic diversity provided evidence of biological invasions by the pathogen within Australia in the states of Western Australia and New South Wales and helped unravel the pattern of invasion beyond Australia into New Zealand, Brazil and Uruguay. No significant genetic differences in pathogen populations collected in native forests and commercial plantations were observed. This emphasizes the importance of sanitation in the acquisition of nursery stock for the establishment of commercial plantations. [ABSTRACT FROM AUTHOR]

The Cryphonectriaceae accommodates some of the world's most important tree pathogens, including four genera known from native and introduced Myrtales in Africa. Surveys in the past 3 y in southern Africa have led to the discovery of cankers with fruiting structures resembling those of the Cryphonectriaceae on trees in the Myrtales in Namibia, South Africa, Swaziland and Zambia. These fungi were identified with morphological characteristics and DNA sequence data. For the first time we report Chrysoporthe austroafricana from Namibia and on Syzygium guineense and Holocryphia eucalypti in Swaziland on a Eucalyptus grandis clone. The host and geographic ranges of Celoporthe dispersa are expanded to include S. legatti in South Africa and S. guineense in Zambia. In addition a monotypic genus, Latruncellus aurorae gen. sp. nov., is described from Galpinia transvaalica (Lythraceae, Myrtales) in Swaziland. The present and other recent studies clearly emphasize the limited understanding of the diversity and distribution of fungi in the Cryphonectriaceae in Africa. [ABSTRACT FROM AUTHOR]

Sexual reproduction in fungi involves either a single individual (selfing) or two individuals (outcrossing). To investigate the roles that these two strategies play in the establishment of an invasive alien pathogen, the Eucalyptus leaf-infecting fungus, Teratosphaeria ( Mycosphaerella) nubilosa was studied. Specifically, the genetic diversity of the pathogen was investigated at micro and macrospatial scales. Interestingly, while data obtained at microspatial scales show clearly that selfing is the main reproductive strategy, at macrospatial scales the population genetic structure was consistent with a genetically outcrossing organism. Additional analyses were performed to explore these apparently discordant results at different spatial scales and to quantify the contribution of selfing vs. outcrossing to the genotypic diversity. The results clearly show that the fungus has a mixed mating strategy. While selfing is the predominant form of mating, outcrosses must have occurred in the pathogen that increased the genotypic diversity of the fungus over time. This mating strategy, coupled with the high levels of geneflow between distant populations of the pathogen, has created an even distribution of maximum diversity from the smallest (leaf) to largest scales (>500 km), which will make breeding for resistance difficult. These data illustrate the evolutionary potential and danger of the introduction of multiple genotypes of a potentially outcrossing pathogen, especially when it has a high dispersal potential. [ABSTRACT FROM AUTHOR]

The taxonomy of Armillaria in southern South America has received little attention since the work of Singer and others. In this study we examine the morphological traits and cultural features for taxa representing the lineages revealed based on molecular phylogenyi and we link them to previously described taxa based on morphology. Lineages I-IV were identified as Armillaria novae-zelandiae, A. montagnei, A. umbrinobrunnea comb. nov. and A. sparrei respectively. They could be differentiated morphologically based on dimension, features of the epicutis, annulus, stipe, hymenophoral trama and flavor and characteristics in culture. Furthermore there was no evidence of host preference for the species recognized. This is the first study integrating the phylogeny and morphology of Armillaria species from Patagonia, and it provides a foundation for future research on these fungi in South America. [ABSTRACT FROM AUTHOR]

Neofusicoccum parvum and N. ribis are closely related species whose identities often have been confused. These fungal plant pathogens were identified recently as the most abundant species of Botryosphaeriaceae (Ascomycetes) isolated from native Syzygium cordatum trees in South Africa. In another study using multiple gene genealogies from five nuclear loci three undescribed cryptic phylogenetic species as well as N. parvum were identified among 30 of these isolates. The aim of this study was to clarify the identity of the remaining isolates in the N. parvum/N. ribis complex from S. cordatum in South Africa, to describe newly identified cryptic species and to test their pathogenicity. Based on the RNA polymerase II subunit (RPB2) sequence comparisons, the isolates were identified as N. parvum or one of three previously recognized phylogenetic species that are described here as N. cordaticola, N. kwambonambiense and N. umdonicola. These species cannot be separated a priori based on morphological characteristics, although a posteriori analysis of variance showed that the differences in conidial length and width between the species were statistically significant. The isolates of the newly described species as well as N. parvum and N. ribis were tested for pathogenicity on S. cordatum under greenhouse conditions. Isolates representing the three new species were significantly more aggressive than N. parvum and N. ribis with N. kwambonambiense being the most aggressive. This study resolved long-standing questions of identity of species within N. parvum/N. ribis complex and lays a foundation for filrther studies on this group of pathogens. [ABSTRACT FROM AUTHOR]

Phytophthora pinifolia causes a needle and shoot disease in Pinus radiata, referred to as ‘Daño Foliar del Pino’. This newly discovered disease requires intensive research efforts that necessitate the processing of large numbers of samples for which accurate identification, often by people not experienced in Phytophthora taxonomy, is required. The aim of this study was, therefore, to develop species-specific primers for P. pinifolia that amplify the internal transcribed spacer region of the ribosomal operon and the nuclear Ypt1 gene, respectively. The primers were tested over several Phytophthora spp., as well as fungi isolated from P. radiata. In all cases, only P. pinifolia was amplified. In addition to the species-specific primers, a PCR-restriction fragment length polymorphism protocol using available Phytophthora genus-specific primers was also used to generate a species-specific profile for P. pinifolia. This provided a characteristic profile that allows the identification of P. pinifolia, and it could also discriminate between 27 different species of Phytophthora. Both techniques reported in this study make it possible to identify large numbers of P. pinifolia cultures accurately and efficiently, which will be important for both quarantine work and biological research on this important new pathogen. [ABSTRACT FROM AUTHOR]

Correction to: Current Genetics https://doi.org/10.1007/s00294-021-01208-w In the original publication of the article, it states the Accession number is pending at two locations. The original article can be found online at https://doi.org/10.1007/s00294-021-01208-w. [Extracted from the article]

Diplodia pinea and Diplodia scrobiculata are opportunistic pathogens associated with various disease symptoms on conifers that most importantly include die-back and stem cankers. Two viruses with dsRNA genomes, Sphaeropsis sapinea RNA virus 1 and 2 (SsRV1 and SsRV2) are found in D. pinea and an undescribed dsRNA element is known to occur in D. scrobiculata. We have partially characterized the putative RNA-dependent RNA polymerase (RdRp) of the undescribed dsRNA element and designed virus-specific primers from the RdRp regions of all three virus genomes. This made it possible to screen for the presence of the three viruses in a collection of D. pinea and D. scrobiculata isolates using real-time PCR. Triple infections with all three viruses occurred in D. pinea and D. scrobiculata. Co-infections with SsRV1 and SsRV2 were common but found only in D. pinea. Co-infection with SsRV1 and the undescribed dsRNA element was rare and observed only in D. pinea. Single infections with either SsRV1 or SsRV2 were equally common, while the undescribed dsRNA element never occurred alone. SsRV1 occurred alone in both D. pinea and D. scrobiculata while SsRV2 occurred alone only in D. pinea. There were only two instances where the undescribed dsRNA element was observed in D. pinea and it was otherwise found only in D. scrobiculata. This study highlights the complex interactions between the viruses found in the closely related plant pathogenic fungi, D. pinea and D. scrobiculata. It illustrates the importance of not only characterizing viruses infecting fungi but also of determining the interactions between mycoviruses and their fungal hosts. [ABSTRACT FROM AUTHOR]

Species of Cryphonectria include some of the world's most important and devastating tree pathogens. Largely through the application of DNA sequence phylogenies, the taxonomy of these fungi has undergone major changes in recent years. Cryphonectria, including the chestnut blight pathogen Cryphonectria parasitica, has been restricted to species that have semi-immersed stromata, orange and pulvinate conidiomata, and one-septate ascospores. Other species of Cryphonectria with different morphological characteristics have been transferred to new genera that are strongly supported by phylogenetic data. This review represents a summary of the taxonomic changes to species of Cryphonectria sensu lato, and we discuss the impact that these changes might have on the understanding of their ecology, pathology and worldwide distribution. [ABSTRACT FROM AUTHOR]

Botryosphaeria rhodina (anamorph Lasiodiplodia theobromae) is a common endophyte and opportunistic pathogen on more than 500 tree species in the tropics and subtropics. During routine disease surveys of plantations in Australia and Venezuela several isolates differing from L. theobromae were identified and subsequently characterized based upon morphology and ITS and EFI-α nucleotide sequences. These isolates grouped into three strongly supported clades related to but different from the known laxa, B. rhodina and L. gonubiensis, These have been described here as three new species L. vrnezuelensis sp. nov., L. crassifora sp. nov. and L. rubropurpurea sp. nov. The three could he distinguished easily from each other and the two described species of Lasiodiplodia, thus confirming phylogenetic separations. Furthermore all live Lasiodiplodia spp. now recognized separated from Diplodia spp. and Dothiorella spp. with 100% bootstrap support. [ABSTRACT FROM AUTHOR]

Conidiomata of a fungus resembling Chrysoporthe cubensis, a serious canker pathogen of Eucalyptus spp. (Myrtaceae, Myrtales) in tropical and subtropical parts of the world, was found on Eucalyptus grandis in Colombia. Fruiting structures of the fungus could be distinguished from those of C cubensis by their distinctly orange conidiomatal necks. This fungus also was found on several plant species native to Colombia including Tibouchina urvilleana, T. lepidota and Miconia theaezans (Melastomataceae, Myrtales). Morphological comparisons, as well as those based on sequences of the ITS1/ITS2 region of the ribosomal DNA repeat and the β-tubulin gene, were used to characterize this fungus. Its pathogenicity was assessed on various plants from which it has been collected, either in field or greenhouse trials. Phylogenetic analyses showed that isolates reside in a clade distinct from the four clades accommodating Chrysoporthe, Cryphonectria, Endothia and Rostraureum Members of this clade are distinguished by the presence of orange conidiomatal necks with black bases and a unique internal stromatal structure. No teleomorph has been found for this fungus, for which we have provided the name Aurapex penicillata gen. sp. nov. A. penicillata produced only small lesions after inoculation on young T. urvilleana, M. theaezans and E. grandis trees and appears not to be a serious pathogen. [ABSTRACT FROM AUTHOR]

Species of Botryosphaeria are among the most serious pathogens that affect mango trees and fruit. Several species occur on mangoes, and these are identified mainly on the morphology of the anamorphs. Common taxa include Dothiorella dominicana, D. mangiferae (= Natrassia mangiferae), D. aromatica and an unidentified species, Dothiorella 'long'. The genus name Dothiorella, however, is acknowledged as a synonym of Diplodia. This study aimed to characterize and name the Botryosphaeria spp. associated with disease symptoms on mangoes. To achieve this isolates representing all four Dothiorella spp. mentioned above were compared with the anamorphs of known Botryosphaeria spp., based on conidial morphology and DNA sequence data. Two genomic regions were analyzed, namely the ITS rDNA and β-tubulin regions. The morphological and molecular results confirmed that the fungi previously identified from mango as species of Dothiorella belong to Fusicoccum. Dothiorella dominicana isolates were identical to isolates of F. parvum (teleomorph = B. parva). A new epithet, namely F. mangiferum, is proposed for isolates previously treated as D. mangiferae or N. mangiferae. Isolates of D. aromatica were identified as F. aesculi (teleomorph = B. dothidea). A fourth Fusicoccum sp. also was identified as those isolates previously known as Dothiorella 'long'. A key is provided to distinguish these species based on anamorph morphology in culture. This study provides a basis for the identification of Botryosphaeria species from mango, which is important for disease control and to uphold quarantine regulations. [ABSTRACT FROM AUTHOR]

Thielaviopsis basicola is a soil-borne fungal pathogen affecting many important agricultural crops. Little is known regarding the population biology or origin of this pathogen. Polymorphic markers developed for Ceratocystis fimbriata, a species complex phylogenetically closely related to T. basicola, were tested and found not to be useful for T. basicola. In this study 14 primer pairs, seven of which resulted in the amplification of single polymorphic fragments in T. basicola were developed. These primers will enable further studies on this economically important pathogen, and will result in an enhanced understanding of its population structure in different parts of the world. [ABSTRACT FROM AUTHOR]

Pathogens, pests and diseases impact heavily on commercial plantation forestry in South Africa, and must thus be considered in any diversified and adaptive management approach. Two important fungal pathogens of Pinus and Eucalyptus species, respectively, are Sphaeropsis sapinea and Cryphonectria cubensis. The aim of this study was to explore the use of bioclimatic modelling to predict the habitat distribution for these pathogens, and to consider potential distribution patterns under conditions of climate change. High-risk areas identified for Sphaeropsis dieback coincide with the summer rainfall hail belt, emphasising the need for planting resistant Pinus spp. in these regions. A much smaller area of South Africa is predicted to be suitable for the occurrence of C. cubensis than for S. sapinea, but a range shift westward in suitable habitat for C. cubensis is predicted under a climate change scenario. Of concern is that many of these areas are currently being planted with disease susceptible Eucalyptus clones. These preliminary results, and further refinement of the model, will lay a valuable foundation for future risk assessment and strategic management planning in the South African forestry industry. [Copyright &y& Elsevier]

Botryosphaeria dothidea is one of the most commonly reported species in a genus of important pathogens of woody plants. This taxon generally is accepted to represent a species complex, and hence its identity remains unclear. Previous studies either have treated B. dothidea as the valid name for B. ribis and B. berengeriana or argued for them to be separate entities. To add to the confusion, no ex-type cultures are available for either B. dothidea or B. ribis. The aim of the present study, therefore, was to recollect and characterize these fungi and designate a set of reference cultures that can be used in future studies. To this end, morphological, cultural and multi-allelic DNA sequence datasets from the rDNA (ITS 1, 5.8S, and ITS 2), β-tubulin and EF1-α genes were used to fully characterize these species. Botryosphaeria dothidea was found to be distinct from B. ribis, while B. berengeriana was retained as synonym of the former name. Furthermore, Fusicoccum aesculi is accepted as anamorph of B. dothidea, while the anamorph of B. ribis is newly described as F ribis sp. nov. Botryosphaeria ribis could be distinguished from B. parva based on β-tubulin and EF1-α sequence data. A combined phylogeny of the three gene regions used in this study also showed that the genus Botryosphaeria rep resents two distinct phylogenetic assemblages that correspond to species with Diplodia and Fusicoccum anamorphs. [ABSTRACT FROM AUTHOR]

We report the development of eight sets of microsatellite markers for the ascomycete fungus and tree pathogen, Botryosphaeria parva. The primers were identified after cloning and sequencing of fragments amplified using simple sequence repeat (SSR) primers. Genome walking was used to determine unknown sequences on either side of new SSRs. The primers were tested and proved useful in nine other Botryosphaeria species that all have Fusicoccum anamorphs, similar to B. parva. [ABSTRACT FROM AUTHOR]

This review considers current knowledge surrounding species boundaries of the Armillaria root-rot pathogens and their distribution. In addition, a phylogenetic tree using translation elongation factor subunit 1-alpha (tef-1α) from isolates across the globe are used to present a global phylogenetic framework for the genus. Defining species boundaries based on DNA sequence-inferred phylogenies has been a central focus of contemporary mycology. The results of such studies have in many cases resolved the biogeographic history of species, mechanisms involved in dispersal, the taxonomy of species and how certain phenotypic characteristics have evolved throughout lineage diversification. Such advances have also occurred in the case of Armillaria spp. that include important causal agents of tree root rots. This commenced with the first phylogeny for Armillaria that was based on IGS-1 (intergenic spacer region one) DNA sequence data, published in 1992. Since then phylogenies were produced using alternative loci, either as single gene phylogenies or based on concatenated data. Collectively these phylogenies revealed species clusters in Armillaria linked to their geographic distributions and importantly species complexes that warrant further research. [ABSTRACT FROM AUTHOR]

Diaporthe perjuncta is a pathogen of grapevines worldwide. A positive-strand RNA virus, Diaporthe RNA virus (DaRV), occurs in hypovirulent isolates of this fungus. A virus-free isolate from a South African grapevine was transfected with in vitro-transcribed positive strands of DaRV. Based on reverse transcription-PCR and partial sequence analysis, the transfected virus was identified as DaRV. The in vitro-transcribed RNA transcripts used to transfect fungal spheroplasts contained parts of the vector at their distal ends. These vector sequences were separated from the DaRV genome during replication in the new host. The transfected isolate had morphological features that differed from those of the isogenic virus-free strain, including production of a yellow pigment, a decreased growth rate, and lack of sporulation. An apple-based pathogenicity test did not reveal any differences in virulence between the virus-free and DaRV-transfected isolates. This study showed that virus-free fungal hosts can be successfully transfected with viruses other than the Cryphonectria parasitica hypovirus. [ABSTRACT FROM AUTHOR]

• We present two Teratosphaeria destructans genomes from Indonesian strains. • The genomes indicated that this pathogen has a heterothallic mating system. • The PCR assay identified the mating types of at least six Teratosphaeria species. • An uneven distribution of mating types was noted in all T. destructans populations. • Recombination likely plays a minor role in T. destructans reproduction. Teratosphaeria destructans is an aggressive fungal pathogen causing leaf and shoot blight on young Eucalyptus trees in plantations. The disease occurs across tropical and subtropical regions of South East Asia and has recently been found in South Africa. Asexual structures of the pathogen are produced on infected tissues, but sexual structures have never been observed. The aim of this study was to investigate the reproductive biology of T. destructans by characterising its mating type (MAT1) locus and investigating its potential for sexual recombination. We found that T. destructans has a heterothallic mating system, with either the MAT1-1 - 1 and MAT1-1 - 10 genes (MAT1-1 idiomorph) or the MAT1-2-1 and MAT1-2-12 genes (MAT1-2 idiomorph) present in a single individual. With a multiplex PCR assay, it was possible to distinguish the two MAT idiomorphs in several Teratosphaeria species and this approach was applied to six global populations of T. destructans. Although both mating types occurred in the South East Asian populations, a single mating type dominated each population. Isolates from the recent disease outbreak in South Africa comprised only a single mating type. Attempts to induce a sexual cycle in vitro using strains of opposite mating type were not successful. The uneven distribution of mating types in populations of T. destructans and the presence of only an asexual state on infected tissues suggests the absence of or at least a minor role for sexual reproduction where the pathogen occurs on non-native Eucalyptus in plantations. [ABSTRACT FROM AUTHOR]

Abstract: Three anamorph genera of the Botryosphaeriaceae namely Diplodia, Lasiodiplodia and Dothiorella have typically dark, ovoid conidia with thick walls, and are consequently difficult to distinguish from each other. These genera are well-known pathogens of especially pine species. We generated a multiple gene genealogy to resolve the phylogenetic relationships of Botryosphaeriaceae with dark conidial anamorphs, and mapped host associations based on this phylogeny. The multiple gene genealogy separated Diplodia, Lasiodiplodia and Dothiorella and it revealed trends in the patterns of host association. The data set was expanded to include more lineages of the Botryosphaeriaceae, and included all isolates from different host species for which ITS sequence data are available. Results indicate that Diplodia species occur mainly on gymnosperms, with a few species on both gymnosperms and angiosperms. Lasiodiplodia species occur equally on both gymnosperms and angiosperms, Dothiorella species are restricted to angiosperms and Neofusicoccum species occur mainly on angiosperms with rare reports on Southern Hemisphere gymnosperms. Botryosphaeria species with Fusicoccum anamorphs occur mostly on angiosperms with rare reports on gymnosperms. Ancestral state reconstruction suggests that a putative ancestor of the Botryosphaeriaceae most likely evolved on the angiosperms. Another interesting observation was that both host generalist and specialist species were observed in all the lineages of the Botryosphaeriaceae, with little evidence of host associated co-evolution. [Copyright &y& Elsevier]

Abstract: Species of Phaeophleospora are anamorphs of Mycosphaerella and they include some of the most serious foliar pathogens of Eucalyptus spp. grown in plantations worldwide. Pathogens assigned to this genus and occurring on Eucalyptus spp. were previously treated in Kirramyces and they are also phylogenetically closely related to other anamorphs of Mycosphaerella residing in the genus Colletogloeopsis. The primary aim of this study was to consider the appropriate taxonomic placement of these species. To achieve this goal, morphological characteristics and DNA sequence data from the ITS and translation EF1-α gene regions were used to compare the type species P. eugeniae, Phaeophleospora spp. and Colletogloeopsis spp. occurring on eucalypts, using ex-type cultures and herbarium specimens. Phylogenetic data and morphological comparisons supported the separation of P. eugeniae from Phaeophleospora species occurring on eucalypts. The name Phaeophleospora is retained for P. eugeniae and the name Kirramyces is resurrected for the species occurring on eucalypts (genera Eucalyptus, Corymbia, and Angophora). Sequence data from the type specimens of two previously described species of Kirramyces, K. lilianiae and K. delegatensis, show they reside in a clade with other Kirramyces spp. Morphological and DNA sequence comparisons also showed that there is considerable overlap between species of Phaeophleospora and Colletogloeopsis from eucalypts. Based on these findings, Colletogloeopsis is reduced to synonymy with the older Kirramyces and the description of Kirramyces is emended to include species with aseptate, as well as multiseptate, conidia produced in acervuli or pycnidia. Two new species of Kirramyces, K. angophorae and K. corymbiae, are also described. [Copyright &y& Elsevier]

Chrysoporthe cubensis is an important fungal pathogen of Eucalyptus species worldwide. The fungus is also known on many other hosts, all residing in the order Myrtales. Previous studies have suggested that Chr. cubensis might be native to South America and southeast Asia and that it has been introduced into Africa. Recently, surveys have been conducted in eastern and southern Africa to assess the distribution of Chrysoporthe spp. in this region. Chr. cubensis was found on Eucalyptus spp. in Kenya, Malawi and Mozambique. The aim of the study reported here was to determine the genetic diversity of Chr. cubensis populations from these countries. Population diversity studies were conducted using five pairs [ABSTRACT FROM AUTHOR]

Abstract: The pathogen Chrysoporthe cubensis (formerly Cryphonectria cubensis) is best known for the important canker disease that it causes on Eucalyptus species. This fungus is also a pathogen of Syzygium aromaticum (clove), which is native to Indonesia, and like Eucalyptus, is a member of Myrtaceae. Furthermore, C. cubensis has been found on Miconia spp. native to South America and residing in Melastomataceae. Recent surveys have yielded C. cubensis isolates from new hosts, characterized in this study based on DNA sequences for the ITS and β-tubulin gene regions. These hosts include native Clidemia sericea and Rhynchanthera mexicana (Melastomataceae) in Mexico, and non-native Lagerstroemia indica (Pride of India, Lythraceae) in Cuba. Isolates from these hosts and areas group in the sub-clade of C. cubensis accommodating the South American collections of the fungus. This sub-clade also includes isolates recently collected from Eucalyptus in Cuba, which are used to epitypify C. cubensis. New host records from Southeast Asia include exotic Tibouchina urvilleana from Singapore and Thailand and native Melastoma malabathricum (Melastomataceae) in Sumatra, Indonesia. Consistent with their areas of occurrence isolates from the latter collections group in the Asian sub-clade of C. cubensis. DNA sequence comparisons of isolates from Tibouchina lepidota in Colombia revealed that they represent a new sub-clade within the greater Chrysoporthe clade. Isolates in this clade are described as Chrysoporthe inopina sp. nov., based on distinctive morphological differences. [Copyright &y& Elsevier]

Ceratocystis fimbriata is one of the most important pathogens of woody plants in the world. This fungus is also a serious pathogen of Eucalyptus species in various countries and has recently been reported from wounds on these trees in South Africa. Inoculation studies have shown that the fungus can cause disease on Eucalyptus spp. in South Africa, although trees dying in the field due to infection have never been encountered. The origin of C. fimbriata in South Africa is unknown, but there is some phylogenetic evidence that the fungus has a Latin American origin. In this study, microsatellite markers specifically designed for C. fimbriata were used to analyse the population diversity of 80 C. fimbriata isolates from Eucalyptus trees in South Africa. Analyses showed a low gene diversity (H = 0.36) and the population was found to be predominantly clonal (IA = 0.95, P < 0.0001). The genotypic diversity was high (GST = 0.99) and the maximum genotypic diversity was very low (1.23%). These data provide good evidence that C. fimbriata has been introduced into South Africa. [ABSTRACT FROM AUTHOR]

• The first linkage map for a Ceratocystis species was constructed. • Two genes potentially involved in mycelial growth rate of Ceratocystis was identified. • Candidate genes associated with host aggressiveness of two Ceratocystis species were identified. • Four of the linkage groups of C. fimbriata and C. manginecans have reciprocal terminal translocations. Some species of Ceratocystis display strong host specificity, such as C. fimbriata sensu stricto that is restricted to sweet potato (Ipomoea batatas) as host. In contrast, the closely related C. manginecans, infects Acacia mangium and Mangifera indica but is not pathogenic to I. batatas. Despite the economic importance of these fungi, knowledge regarding the genetic factors that influence their pathogenicity and host specificity is limited. A recent inheritance study, based on an interspecific cross between C. fimbriata and C. manginecans and the resultant 70 F 1 progeny, confirmed that traits such as mycelial growth rate, spore production and aggressiveness on A. mangium and I. batatas are regulated by multiple genes. In the present study, a quantitative trait locus (QTL) analysis was performed to determine the genomic loci associated with these traits. All 70 progeny isolates were genotyped with SNP markers and a linkage map was constructed. The map contained 467 SNPs, distributed across nine linkage groups, with a total length of 1203 cm. Using the progeny genotypes and phenotypes, one QTL was identified on the linkage map for mycelial growth rate, one for aggressiveness to A. mangium and two for aggressiveness to I. batatas (P < 0.05). Two candidate genes, likely associated with mycelial growth rate, were identified in the QTL region. The three QTLs associated with aggressiveness to different hosts contained candidate genes involved in protein processing, detoxification and regions with effector genes and high transposable element density. The results provide a foundation for studies considering the function of genes regulating various quantitative traits in Ceratocystis. [ABSTRACT FROM AUTHOR]