Showing papers by "Michael J. Wingfield published in 2010"

Botryosphaeriaceae associated with Terminalia catappa in Cameroon, South Africa and Madagascar

Abstract: Species in the Botryosphaeriaceae represent some of the most important fungal pathogens of woody plants. Although these fungi have been relatively well studied on economically important crops, hardly anything is known regarding their taxonomy or ecology on native or non-commercial tree species. The aim of this study was to compare the diversity and distribution of the Botryosphaeriaceae on Terminalia catappa, a tropical tree of Asian origin planted as an ornamental in Cameroon, Madagascar and South Africa. A total of 83 trees were sampled, yielding 79 Botryosphaeriaceae isolates. Isolates were initially grouped based on morphology of cultures and conidia. Representatives of the different morphological groups were then further characterised using sequence data for the ITS, tef 1-alpha, rpb2, BOTF15 and beta-tub gene regions. Five species of the Botryosphaeriaceae were identified, including Neofusicoccum parvum, N. batangarum sp. nov., Lasiodiplodia pseudotheobromae, L. theobromae and L. mahajangana sp. nov. Lasiodiplodia pseudotheobromae and L. theobromae, were the most commonly isolated species (62%), and were found at all the sites. Neofusicoccum parvum and N. batangarum were found in South Africa and Cameroon, respectively, whereas L. mahajangana was found only in Madagascar. Greenhouse inoculation trials performed on young T. catappa trees showed variation among isolates tested, with L. pseudotheobromae being the most pathogenic. The Botryosphaeriaceae infecting T. catappa appear to be dominated by generalist species that also occur on various other hosts in tropical and sub-tropical climates.

Endophytic and canker-associated Botryosphaeriaceae occurring on non-native Eucalyptus and native Myrtaceae trees in Uruguay

Abstract: Species of the Botryosphaeriaceae are important pathogens causing cankers and die-back on many woody plants. In Uruguay, Neofusicoccum eucalyptorum, N. ribis and B. dothidea have previously been associated with stem cankers on plantation-grown Eucalyptus globulus. However, very little is known regarding the occurrence and species diversity of Botryosphaeriaceae in native Myrtaceae forests or what their relationship is to those species infecting Eucalyptus in plantations. The objectives of this study were to identify the Botryosphaeriaceae species present as endophytes or associated with cankers in both introduced and native tree hosts in Uruguay, and to test the pathogenicity of selected isolates obtained from native trees on Eucalyptus. Symptomatic and asymptomatic material was collected countrywide from Eucalyptus plantations and native Myrtaceae trees. Single spore cultures were identified based on conidial morphology and comparisons of DNA sequences of the ITS and EF1-α regions. Six Botryosphaeriaceae species were identified. Botryosphaeria dothidea, N. eucalyptorum and specimens residing in the N. parvum-N. ribis complex were isolated from both introduced Eucalyptus and native Myrtaceae trees, whereas Lasiodiplodia pseudotheobromae was found only on Myrcianthes pungens. Diplodia pseudoseriata sp. nov. and Spencermartinsia uruguayensis sp. nov. are novel species found only on native myrtaceous hosts. Pathogenicity tests showed that isolates obtained from native trees and identified as L. pseudotheobromae, N. eucalyptorum and the N. parvum-N.ribis complex are pathogenic to E. grandis. Interestingly, Lasiodiplodia pseudotheobromae has not previously been found on Eucalyptus in Uruguay and represents a potential threat to this host.

Complex interactions among host pines and fungi vectored by an invasive bark beetle

Abstract: Summary • Recent studies have investigated the relationships between pairs or groups of exotic species to illustrate invasive mechanisms, but most have focused on interactions at a single trophic level. • Here, we conducted pathogenicity tests, analyses of host volatiles and fungal growth tests to elucidate an intricate network of interactions between the host tree, the invasive red turpentine beetle and its fungal associates. • Seedlings inoculated with two strains of Leptographium procerum isolated from Dendroctonus valens in China had significantly longer lesions and higher mortality rates than seedlings inoculated with other fungal isolates. These two strains of L. procerum were significantly more tolerant of 3-carene than all other fungi isolated there, and the infection of Chinese pine (Pinus tabuliformis) seedlings by these two strains enhanced the production and release of 3-carene, the main attractant for D. valens, by the seedlings. • Our results raise the possibility that interactions among the fungal associates of D. valens and their pine hosts in China may confer advantages to these strains of L. procerum and, by extension, to the beetles themselves. These interactions may therefore enhance invasion by the beetle–fungal complex.

Novel associations between pathogens, insects and tree species threaten world forests

Abstract: OECD, DST/NRF Centre of Excellence in Tree Health Biotechnology (CTHB), National Research Foundation (NRF)

DNA bar-coding reveals source and patterns of Thaumastocoris peregrinus invasions in South Africa and South America

Abstract: Thaumastocoris peregrinus is a recently introduced invertebrate pest of non-native Eucalyptus plantations in the Southern Hemisphere. It was first reported from South Africa in 2003 and in Argentina in 2005. Since then, populations have grown explosively and it has attained an almost ubiquitous distribution over several regions in South Africa on 26 Eucalyptus species. Here we address three key questions regarding this invasion, namely whether only one species has been introduced, whether there were single or multiple introductions into South Africa and South America and what the source of the introduction might have been. To answer these questions, bar-coding using mitochondrial DNA (COI) sequence diversity was used to characterise the populations of this insect from Australia, Argentina, Brazil, South Africa and Uruguay. Analyses revealed three cryptic species in Australia, of which only T. peregrinus is represented in South Africa and South America. Thaumastocoris peregrinus populations contained eight haplotypes, with a pairwise nucleotide distance of 0.2-0.9% from seventeen locations in Australia. Three of these haplotypes are shared with populations in South America and South Africa, but the latter regions do not share haplotypes. These data, together with the current distribution of the haplotypes and the known direction of original spread in these regions, suggest that at least three distinct introductions of the insect occurred in South Africa and South America before 2005. The two most common haplotypes in Sydney, one of which was also found in Brisbane, are shared with the non-native regions. Sydney populations of T. peregrinus, which have regularly reached outbreak levels in recent years, might thus have served as source of these three distinct introductions into other regions of the Southern Hemisphere.

Ophiostoma spp. associated with pine- and spruce-infesting bark beetles in Finland and Russia

Abstract: The timber and pulp industries of Finland rely heavily on importations from Russia as source of raw timber. These imports raise the risk of accidentally importing forest pests and pathogens, especially bark beetles and their associated fungi, into Finland. Although ophiostomatoid fungi have previously been reported from Finland and Russia, the risks of accidentally moving these fungi has prompted a first survey to compare the diversity of conifer-infesting bark beetles and associated fungi from boreal forests on both sides of the Finnish-Russian border. The aim of the present study was to identify and characterise Ophiostoma species isolated in association with 11 bark beetle species infesting Pinus sylvestris and Picea abies during this survey in the eastern parts of Finland and neighbouring Russia. Fungal isolates were grouped based on morphology and representatives of each mor- phological group were subjected to DNA sequence comparisons of the internal transcribed spaced region (ITS1, 5.8S, ITS2) and β-tubulin gene region. A total of 15 species of Ophiostoma were identified, including seven known species, five new species, and three species for which the identity remains uncertain. In the O. piceae-complex we identified O. canum, O. floccosum, O. karelicum and O. rachisporum sp. nov., and related to these, some isolates belonging to the European clade of O. minus in the O. minus-complex. Ophiostoma bicolor and O. fuscum sp. nov. were identified in the O. ips-complex, while O. ainoae, O. brunneo­ciliatum, O. tapionis sp. nov. and O. pallidulum sp. nov. were shown to group close to, but not in a strict monophyletic lineage with species of the O. ips-complex. Together with a single O. abietinum-like isolate, the only species that grouped close to the Sporothrix schenckii­ O. stenoceras complex, was O. saponiodorum sp. nov.

Calonectria species associated with cutting rot of Eucalyptus

Abstract: Decline in the productivity of Eucalyptus hybrid cutting production in the Guangdong Province of China is linked to cutting rot associated with several Calonectria spp. The aim of this study was to identify these fungi using morphological and DNA sequence comparisons. Two previously undescribed Calonectria spp., Ca. pseudoreteaudii sp. nov. and Ca. cerciana sp. nov. were identified together with Ca. pauciramosa. Calonectria pseudoreteaudii resides in the Ca. reteaudii complex and Ca. cerciana is closely related to Ca. morganii. Connected to the dis- covery of Ca. pseudoreteaudii, species in the Ca. reteaudii complex were re-considered and the group is shown to accommodate two cryptic species. These originate from Australia and are described as Ca. queenslandica sp. nov. and Ca. terrae-reginae sp. nov.

Micro- and macrospatial scale analyses illustrates mixed mating strategies and extensive geneflow in populations of an invasive haploid pathogen

Abstract: 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.

Re-evaluation of Cryptosporiopsis eucalypti and Cryptosporiopsis-like species occurring on Eucalyptus leaves.

Abstract: Cryptosporiopsis eucalypti is a common follic- olous pathogen of Eucalyptus species in tropical and temperate regions where these trees are grown in planta- tions. The taxonomy of C. eucalypti is confused by the fact that it is phylogenetically unrelated to the type species of Cryptosporiopsis (Cryptosporiopsis nigra = C. scutellata, Helotiales). The aim of this study was to resolve the taxonomic position of C. eucalypti based on morphology and phylogenetic inference. Thirty-two Eucalyptus leaf samples with symptoms typical of C. eucalypti infection were collected from 10 tropical and temperate countries across four continents. Cultures were established from single conidia, as well as from ascospores of a previously unreported teleomorph state. DNA sequences were obtained for the 28 S nrDNA, the internal transcribed spacers of the nrDNA operon, and beta-tubulin regions to determine generic and species-level relationships. DNA- sequence analysis showed that conidial and ascospore isolates of C. eucalypti have low intraspecific variation, although two collections from Australia and one from Uruguay represented two novel taxa. Based on the newly collected teleomorph stage, as well as the phylogenetic data, C. eucalypti is shown to represent a new genus closely related to Plagiostoma (Gnomoniaceae, Diapor- thales) for which the names Pseudoplagiostoma gen. nov. and Pseudoplagiostomaceae fam. nov. (Diaporthales )a re introduced. Two new species of Cryptosporiopsis (Der- mateaceae, Helotiales) on Eucalyptus from Australia and California (USA) are also described.

Two new Ophiostoma species from Protea caffra in Zambia.

Abstract: The genus Ophiostoma (Ophiostomatales) has a global distribution and species are best known for their association with bark beetles (Curculionidae: Scolytinae) on conifers. An unusual assemblage of these fungi is closely associated with the African endemic plant genus Protea (Proteaceae). Protea-associated Ophiostoma species are ecologically atypical as they colonise the fruiting structures of various serotinous Protea species. Seven species have been described from this niche in South Africa. It has been speculated that novel species may be present in other African countries where these host plants also occur. This view was corroborated by recent collections of two unknown species from Protea caffra trees in Zambia. In the present study we evaluate the species delineation of these isolates using morphological comparisons with other Protea-associated species, differential growth studies and analyses of DNA sequence data for the β-tubulin and internal transcribed spacer (ITS1, 5.8S, ITS2) regions. As a result, the species O. protea-sedis sp. nov., and O. zambiensis sp. nov. are described here as new. This study brings the number of Protea-associated Ophiostoma species to nine and highlights the need for more inclusive surveys, including additional African countries and hosts, to elucidate species diversity in this uncharacteristic niche.

Ophiostoma tsotsi sp. nov., a wound-infesting fungus of hardwood trees in Africa

Abstract: Polymorphic sequence-characterised marker assays from a recent diversity study on the Ascomycete fungus Ophiostoma quercus reported that some isolates from Africa were genetically distinct from O. quercus. In the present study, these African isolates were compared with authentic O. quercus isolates by evaluating morphological characters, growth in culture, mating compatibility and DNA sequence data. The isolates from Africa were morphologically similar to O. quercus, presenting Pesotum and Sporothrix synanamorphs in culture. Phylogenetic analyses of the ribosomal internal transcribed spacer regions 1 and 2, β-tubulin and translation elongation factor 1-α gene regions confirmed that the African group represents a distinct species within the hardwood lineage of the O. piceae complex, closely related to O. ulmi and O. himal-ulmi. Mating studies between O. quercus and the African isolates showed that isolates mated predominantly with those of their own group, although there were rare cases of fertile crosses between the groups. Isolates residing in the African lineage are described here as a new species, O. tsotsi sp. nov.

New Ceratocystis species infecting coffee, cacao, citrus and native trees in Colombia

Abstract: Ceratocystis fimbriata sensu lato includes a large number of plant and especially tree pathogens. In Colombia, isolates of this fungus cause a serious canker-stain disease on coffee as well as other fruit trees. Large collections of these isolates have been shown to occur in two distinct phylogenetic lineages based on ITS sequence comparisons. The aim of this study was to compare representatives of these two groups of isolates from coffee, citrus, cacao and native trees in Colombia, based on morphology and DNA-sequences for three gene regions. Host-specificity of the fungus was also considered. Representatives of the two groups of isolates were morphologically distinct and could be distinguished based on DNA sequence comparisons. They are also distinct from other species in the C. fimbriata sensu lato species complex and the sweet potato pathogen C. fimbriata sensu stricto and are provided with the names C. colombiana sp. nov and C. papillata sp. nov. There was no evidence for host-specificity amongst isolates of these two fungi that collectively represent a serious threat to coffee production in Colombia.

Identification and Pathogenicity of Chrysoporthe cubensis on Eucalyptus and Syzygium spp. in South China

Abstract: The genus Chrysoporthe includes important pathogens of plantation-grown Eucalyptus spp. and has been reported from several tree genera in the order Myrtales in tropical and subtropical areas of the world. During disease surveys in South China, fruiting structures typical of Chrysoporthe spp. were observed on cankers on Eucalyptus spp. and Syzygium cumini trees. The aim of this study was to confirm the identity of the Chrysoporthe cubensis infecting the Eucalyptus spp. and S. cumini and to test the pathogenicity of the fungus. Following glasshouse trials to select virulent isolates, field inoculations were undertaken to screen different commercial Eucalyptus genotypes for their susceptibility to the fungus. Isolates were characterized based on their morphology and DNA sequence data for the β-tubulin and internal transcribed spacer regions of the ribosomal DNA. Results showed that the putative pathogen represented the Asian form of C. cubensis, which occurred on numerous different Eucalyptus spp. and hybrid clones as well as S. cumini. Field inoculations showed that all six of the Eucalyptus genotypes tested are susceptible to infection by C. cubensis. Significant differences were observed between them, providing prospects to select disease-tolerant planting stock in the future.

Characterisation of synnematous bark beetle-associated fungi from China, including Graphium carbonarium sp. nov.

Abstract: Ophiostomatoid fungi on trees are typically bark beetle associates that cause sapstain in timber and some are pathogens. Very little is known regarding the ophiostomatoid fungi associated with bark beetles in China and the aim of this study was to identify a collection of these fungi with synnematous anamorphs. Micromorphology and DNA sequences of the internal transcribed spacer regions (ITS) of the ribosomal DNA and the partial β-tubulin gene were used for identifications. The isolates could be divided in six morphological groups. DNA sequence comparisons with published data confirmed that these groups represented six species, four in the Ophiostomatales (Sordariomycetidae) and two in the Microascales (Hypocreomycetidae). The majority of these were isolated from conifer hosts. Ophiostoma quercus, O. setosum, Pesotum fragrans (Ophiostomatales) and Graphium pseudormiticum (Microascales) were found on Tsuga dumosa infested by a Pissodes sp. In addition, O. quercus and P. fragrans were found associated with Tomicus yunnanensis on Pinus yunnanensis, P. fragrans with a Pissodes sp. on P. armandi, and O. piceae with Ips subelongatus on Larix olgensis. Only two species, O. quercus and a new species in the Graphium penicilliodes complex, described here as Graphium carbonarium sp. nov., were isolated from Pissodes galleries on Salix babylonica. These results include several new fungus-host and fungus-insect associations, and G. pseudormiticum is reported here for the first time from China.

Taxonomy and pathogenicity of two novel Chrysoporthe species from Eucalyptus grandis and Syzygium guineense in Zambia

Abstract: Among fungi in the Cryphonectriaceae, Cryphonectria parasitica, the causal agent of chestnut blight, and Chrysoporthe spp., inducing stem cankers and death of plantation-grown Eucalyptus spp., constitute some of the most important tree pathogens. During a survey to determine diseases and related pathogens associated with native and non-native Myrtales in Zambia, two fungi resembling stem canker pathogens in the genus Chrysoporthe were recovered from Syzygium guineense and Eucalyptus grandis. We undertook this study to characterise the fungi, using DNA sequence comparisons and morphological features. Inoculation tests were also conducted in a greenhouse to assess their pathogenicity on Eucalyptus spp. Results showed distinct phenotypic differences between isolates collected from Zambia and existing species of Chrysoporthe, and phylogenetic analyses demonstrated that the Zambian isolates represent previously undescribed species of Chrysoporthe. These isolates, which have been named Chrysoporthe zambiensis sp. nov. and Chrysoporthe syzygiicola sp. nov., are only known from their anamorphic states. Both species were found to be pathogenic to Eucalyptus. The description of Chr. zambiensis and Chr. syzygiicola with teleomorph names, led to the new combination Chrysoporthe hodgesiana for the only anamorphic species in Chrysoporthe, Chrysoporthella hodgesiana, to ensure more stable and less confusing taxonomy for Chrysoporthe.

Eight new Leptographium species associated with tree-infesting bark beetles in China

Abstract: Leptographium spp. are anamorphs of Grosmannia residing in the order Ophiostomatales. These fungi are typically associated with bark-beetles and are common causal agents of sapstain in lumber and some are important tree pathogens. In this study, Leptographium spp. associated with bark beetles collected during a survey in Jilin and Yunnan provinces of China, were identified. Identifications were achieved using comparisons of morphologi- cal characters and DNA sequence data for the ITS2-partial LSU rDNA region, as well as the β-tubulin and EF-1α gene regions. Eight unknown species of Leptographium are recognised and described from conifer and hardwood hosts, associated with beetles including Ips subelongatus, Tomicus yunnanensis, Hylurgops minor, Polygraphus verrucifrons and a Pissodes sp. Six of the new species are morphologically and phylogenetically related to species known to occur in Asia such as G. yunnanense, L. bhutanense, L. bistatum and L. sinoprocerum. The remaining two taxa are related to those in a group containing G. americana and L. abietinum, found in North America. This study also provides the first report of L. pineti on Pinus kesiya in China.

Cryptometrion aestuescens gen. sp. nov. (Cryphonectriaceae) pathogenic to Eucalyptus in Indonesia

Abstract: The recently described Cryphonectriaceae (Diaporthales) includes numerous important tree pathogens such as the chestnut blight pathogen Cryphonectria parasitica, and various species of Chrysoporthe that cause serious stem canker diseases on Eucalyptus. A recent investigation of dying Eucalyptus grandis clonal hedges in northern Sumatra, Indonesia, revealed the presence of an unknown member of the Cryphonectriaceae. DNA sequence comparisons with other members of the Cryphonectriaceae showed that the Indonesian fungus represents a new genus and species in the family, for which we provide the name Cryptometrion austuescens gen. sp. nov. It can be distinguished from other Cryphonectriaceae on Eucalyptus, such as Chrysoporthe, Microthia, Holocryphia and Cryphonectria, based on its orange, limited stromatic tissue, single septate, fusoid to ellipsoid ascospores and the absence of paraphyses among the conidiogenous cells in the anamorph. Inoculations with this fungus on two clones of E. grandis showed that it is highly pathogenic and has the capacity to cause serious losses to Eucalyptus plantations in the region.

Three new Graphium species from baobab trees in South Africa and Madagascar.

Abstract: Baobabs (Adansonia spp.) are iconic trees, known for their immense size, strange forms, sources of food and as the subjects of myths and mysteries. It is thus surprising that little is known regarding the fungi that infect these trees. During a survey to determine which wound infecting fungi occur on baobabs, synnematous structures were observed and Graphium-like isolates were obtained. Culture characteristics and micro-morphology, together with DNA sequence comparisons for the SSU rRNA, rRNA-ITS and TEF-1α gene regions were used to charac- terise these fungi. These data revealed three novel Graphium spp. and these are described as G. adansoniae, G. madagascariense and G. fabiforme.

Aurifilum, a new fungal genus in the Cryphonectriaceae from Terminalia species in Cameroon

Abstract: Native Terminalia spp. in West Africa provide a popular source of construction timber as well as medical, spiritual and social benefits to rural populations. Very little is, however, known regarding the diseases that affect these trees. During an investigation into possible diseases of Terminalia spp. in Cameroon, orange to yellow fungal fruiting structures, resembling those of fungi in the Cryphonectriaceae, were commonly observed on the bark of native Terminalia ivorensis, and on dead branches of non-native Terminalia mantaly. In this study the fungus was identified based on morphological features as well as DNA sequence data (ITS and β-tubulin) and its pathogenicity was tested on T. mantaly seedlings. Our results showed that isolates of this fungus represent a previously undescribed genus in the Cryphonectriaceae, which we describe as Aurifilummarmelostoma gen. et sp. nov. Pathogenicity tests revealed that A. marmelostoma is pathogenic on T. mantaly. These tests, and the association of A. marmelostoma with disease symptoms on T. ivorensis, suggest that the fungus is a pathogen of this important tree.

Genetic diversity in the Eucalyptus stem pathogen Teratosphaeria zuluensis

Abstract: Coniothyrium canker caused by the fungal pathogen Teratosphaeria (= Coniothyrium) zuluensis is one of the most important diseases affecting plantation-grown Eucalyptus trees. Little is known regarding the pathogen and this study consequently considers the genetic diversity and population structure of T. zuluensis. Eleven microsatellites markers, of which six were developed in this study, were used to analyse two temporally separated populations of T. zuluensis from South Africa, one population from Malawi and one population from China. Results showed that the populations of T. zuluensis have a moderate to high diversity and that clonal reproduction is predominant. There was also evidence that the genetic diversity of the pathogen in South Africa has increased over time. Comparison of T. zuluensis populations from South Africa, Malawi and China suggest that South Africa is most probably not the centre of origin of the pathogen as has previously been suggested.

New and rare coelomycetes with appendage-bearing conidia from Pondoland, South Africa

Abstract: During a mycological excursion to the Pondoland region of South Africa in 2008, six interesting anamorphic fungi with appendage-bearing conidia were isolated. They are Bartalinia pondoensis, Crucellisporium umtamvunae, and Mycohypallage margaretae, all of which are new to science, Mycohypallage congesta with a new observation of gelatinous basal appendage, Mycotribulus mirabilis on a new host plant, Apodytes, and Chaetospermum camelliae. Morphological characters are described and notes provided. The teleomorphic affinity of C. umtamvunae to the Helotiales is proposed based on DNA sequence data.

Taxonomy of Armillaria in the Patagonian forests of Argentina.

Abstract: 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 molecu- lar phylogeny, 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.