Showing papers by "Michael J. Wingfield published in 2007"

Puccinia psidii: a threat to the Australian environment and economy a review

Abstract: Puccinia psidii causes a rust disease on a broad range of hosts in the Myrtaceae and Heteropyxidaceae. It is native to South America where it can cause severe disease in eucalypt plantations and other introduced Myrtaceae. The pathogen has recently expanded its geographical range to Hawaii, increasing concerns about the potential for an incursion in Australia. This paper reviews the taxonomy, biology, impact and options for control of P. psidii. It also discusses the probable impact if an incursion were to occur in Australia and the preparations that must be made to mitigate adverse consequences.

A comparison of control results for the alien invasive woodwasp, Sirex noctilio, in the southern hemisphere.

Abstract: Sirex noctilio has resulted in one of the most damaging biological invasions of pine forestry in the southern hemisphere. 2 An intensive, integrated control programme has been developed for this pest and is generally considered very successful. However, a critical comparison of S. noctilio infestations and control efforts throughout the southern hemisphere reveals that control has not been uniformly effective. Of particular concern is the apparently unexplained variability in establishment and success of biological control agents, including various parasitic wasps and the parasitic nematode Deladenus siricidicola . 3 An overlooked aspect in the establishment of the biological control interventions for S. noctilio is the potential influence of genetic bottlenecks on the ability of the agents to adapt to different environments and different populations of S. noctilio . 4 Despite established biological control agents, stress in forests caused by silvicul- tural practices or the environment will predispose trees to heavy infestation. Unfortunately, improved silvicultural practices are not always economically feasible and environmental changes are often unavoidable. 5 Sirex noctilio continues to pose a serious threat to pine forestry in many areas. Despite extensive earlier research into a single integrated control for S. noctilio , it is important to recognize that such a strategy will probably require significant local adaptation in new areas of infestation and over time.

Taxonomy, phylogeny and identification of Botryosphaeriaceae associated with pome and stone fruit trees in South Africa and other regions of the world

Abstract: We acknowledge financial support of the National Research Foundation, the Tree Protection Co-operative Programme and the THRIP initiative of the Department of Trade and Industry, South Afric

Tolerance in banana to Fusarium wilt is associated with early up-regulation of cell wall-strengthening genes in the roots

Abstract: SUMMARY Fusarium wilt, caused by the fungal pathogen Fusarium oxysporum f. sp. cubense (Foc), is one of the most destructive diseases of bananas. In the tropics and subtropics, Cavendish banana varieties are highly susceptible to Foc race 4 (VCG 0120). Cavendish selection GCTCV-218 was shown to have significantly lower disease severity and incidence compared with susceptible cultivar Williams in replicated greenhouse and field trials. Suppression subtractive hybridization (SSH) was previously carried out to identify genes induced in roots of GCTCV-218, but not in Williams, after infection with Foc'subtropical' race 4. Seventy-nine SSH clones were sequenced and revealed 13 non-redundant gene fragments, several of which showed homology to defence-associated genes, including cell wall-strengthening genes. Quantitative RT-PCR was used to confirm up-regulation and differential expression of a number of genes throughout a time-course, following Foc infection in the tolerant GCTCV-218 when compared with susceptible cv. Williams. Tolerance of GCTCV-218 was linked to significantly increased induction of cell wall-associated phenolic compounds.

Ceratocystis manginecans sp. nov., causal agent of a destructive mango wilt disease in Oman and Pakistan

Abstract: Department of Genetics, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Pretoria 0002, South Africa Ghadafan Agriculture Research Station, Ministry of Agriculture and Fisheries, P. O. Box 204 Sohar, 311, Sultanate of Oman Plant Protection Division, Nuclear Institute for Agriculture and Biology (NIAB), P.O. Box 128, Jhang Road, Faisalabad, Pakistan Department of Crop Sciences, P.O. Box 34, Sultan Qaboos University, Al Khod 123, Sultanate of Oman Department of Plant Pathology, University of Florida, IFAS Tropical Research and Education, Homestead, FL 33031-3314 USA

Human Impacts in Pine Forests: Past, Present, and Future*

Abstract: Pines (genus Pinus) form the dominant tree cover over large parts of the Northern Hemisphere. Human activities have affected the distribution, composition, and structure of pine forests for millen- nia. Different human-mediated factors have affected different pine species in different ways in different regions. The most important factors affecting pine forests are altered fire regimes, altered grazing/ browsing regimes, various harvesting/construction activities, land clearance and abandonment, purposeful planting and other manip- ulations of natural ecosystems, alteration of biotas through species reshuffling, and pollution. These changes are occurring against a backdrop of natural and anthropogenically driven climate change. We review past and current influence of humans in pine forests, seeking broad generalizations. These insights are combined with perspectives from paleoecology to suggest probable trajectories in the face of escalating human pressure. The immense scale of impacts and the complex synergies between agents of change calls for urgent and multifaceted action.

First outbreak of pitch canker in a South African pine plantation

Abstract: Fusarium circinatum, the causal agent of pitch canker, was first reported in South Africa in 1990 on Pinus patula seedlings in a nursery. Subsequent to this outbreak the pathogen has spread throughout South African pine nurseries causing a serious root and collar rot disease of various Pinus spp. The stem canker disease on plantation trees that typifies pitch canker in other parts of the world has never been observed in South Africa. An outbreak of a serious disease with symptoms resembling those of pitch canker on 5- and 9-year-old P. radiata in the Western Cape Province, prompted a study to determine the causal agent. Besides having stem cankers exuding copious amounts of resin, dying trees were infested by the weevil, Pissodes nemorensis. Isolations were thus made from infected tissue, weevil galleries and from adult insects. A Fusarium sp. was consistently isolated from both pine tissue and insects. The fungus was characterised based on morphological features and using DNAsequence comparisons for the genes encoding translation elongation factor 1-α and β-tubulin. These studies showed conclusively that the fungus represents the pitch canker fungus, F. circinatum. Three isolates from trees in the affected area were inoculated onto P. radiata seedlings and their ability to cause disease was thus evaluated. Three weeks after inoculation, die-back symptoms were recorded on all inoculated plants. This report represents the first outbreak of pitch canker on plantation trees in South Africa. The fungus can thus no longer be considered only as a nursery pathogen in the country, where it seriously threatens the future of plantation forestry.

Characterization and Distribution of Mating Type Genes in the Dothistroma Needle Blight Pathogens

Abstract: Groenewald, M., Barnes, I., Bradshaw, R. E., Brown A. V., Dale, A., Groenewald, J. Z., Lewis, K. J., Wingfield, B. D., Wingfield, M. J., and Crous, P. W. 2007. Characterization and distribution of mating type genes in the Dothistroma needle blight pathogens. Phytopathology 97:825-834. Dothistroma septosporum and D. pini are the two causal agents of Dothistroma needle blight of Pinus spp. in natural forests and plantations. Degenerate primers amplified portions of mating type genes (MAT1-1-1 and MAT1-2) and chromosome walking was applied to obtain the fulllength genes in both species. The mating-type-specific primers designed in this study could distinguish between the morphologically similar D. pini and D. septosporum and between the different mating types of these species. Screening of isolates from global collections of D. septosporum showed that only MAT2 isolates are present in Australian and New Zealand collections, where only the asexual form of the fungus has been found. In contrast, both mating types of D. septosporum were present in collections from Canada and Europe, where the sexual state is known. Intriguingly, collections from South Africa and the United Kingdom, where the sexual state of the fungus is unknown, included both mating types. In D. pini, for which no teleomorph is known, both mating types were present in collections from the United States. These results provided new insights into the biology and global distribution of two of the world’s most important pine pathogens and should facilitate management of the diseases caused by these fungi.

Ophiostoma species (Ascomycetes: Ophiostomatales) associated with bark beetles (Coleoptera: Scolytinae) colonizing Pinus radiata in northern Spain.

Abstract: Bark beetles (Coleoptera: Scolytinae) are known to be associated with fungi, especially species of Ophiostoma sensu lato and Ceratocystis. However, very little is known about these fungi in Spain. ...

Testing of selected South African Pinus hybrids and families for tolerance to the pitch canker pathogen, Fusarium circinatum

Abstract: Plantations of Pinus spp constitute approximately 50% of the South African forestry industry The first aim of this study was to develop a reliable inoculation technique to screen Pinus spp, for tolerance to infection by F circinatum, which threatens pine forestry in South Africa Inoculation of branches was compared with stem inoculations and we considered the number of branches or trees required to obtain statistically significant results Furthermore, variation in the susceptibility of some Pinus families, clones and hybrids was considered Results showed that branch inoculations were closely correlated with those from stem inoculations, and that it is important to consider branch and stem diameters when assessing susceptibility of trees Subsequent trials using branch inoculations showed significant differences in F circinatum tolerance amongst a range of pine species and hybrids of potential interest to forestry in South Africa Significant differences in susceptibility were also found among clones of two P radiata families The most tolerant trees were P elliottii × caribaea and P patula × oocarpa hybrids, while the most susceptible species were P patula, P greggii and hybrids of these two This is the first trial considering the susceptibility of Pinus hybrids, Pinus clones and some P patula provenances, and the results indicate excellent potential for breeding for tolerance to pitch canker in South Africa

Discovery of Fungus-Mite Mutualism in a Unique Niche

Abstract: The floral heads (infructescences) of South African Protea L. represent a most unusual niche for fungi of the economically important genus Ophiostoma Syd. and P. Syd. emend. Z.W. de Beer et al. Current consensus holds that most members of Ophiostoma are vectored by tree-infesting bark beetles. However, it has recently been suggested that mites, phoretic on these bark beetles, may play a central role in the dispersal of Ophiostoma. No bark beetles are known from Protea. Therefore, identifying the vectors of Ophiostoma in Protea infructescences would independently evaluate the role of various arthropods in the dispersal of Ophiostoma. Infructescence-colonizing arthropods were tested for the presence of Ophiostoma DNA using polymerase chain reaction (PCR) and for reproductive propagules by isolation on agar plates. PCR tests revealed that few insects carried Ophiostoma DNA. In contrast, various mites (Proctolaelaps vandenbergi Ryke, two species of Tarsonemus Canestrini and Fonzago, and one Trichouropoda Berlese species) frequently carried Ophiostoma propagules. DNA sequence comparisons for 28S ribosomal DNA confirmed the presence of O. splendens G. J. Marais and M. J. Wingf., O. palmiculminatum Roets et al., and O. phasma Roets et al. on these mites. Two apparently undescribed species of Ophiostoma were also identified. Light and scanning electron microscopy revealed specialized structures in Trichouropoda and one Tarsonemus sp. that frequently contained Ophiostoma spores. The Trichouropoda sp. was able to complete its life cycle on a diet consisting solely of its identified phoretic Ophiostoma spp. This study provides compelling evidence that mites are the primary vectors of infructescence-associated Ophiostoma spp. in South Africa.

Species-specific primers for Fusarium redolens and a PCR-RFLP technique to distinguish among three clades of Fusarium oxysporum.

Abstract: The currently available morphological and molecular diagnostic techniques for Fusarium redolens and the three phylogenetic clades of Fusarium oxysporum are problematic. Aligned translation elongation factor 1α (TEF-1α) gene sequences from these species and their close relatives were used to design F. redolens-specific primers, and to identify restriction sites that discriminate among the three clades of F. oxysporum. The F. redolens-specific primers distinguished this species from all others included in the study. There were three TEF-1α-RFLP patterns among formae speciales of F. oxysporum. These PCR-RFLP patterns corresponded with the three clades. These techniques provide simple and inexpensive diagnostic methods for the identification of F. redolens and members of the three clades of F. oxysporum.

Occurrence of the wattle wilt pathogen, Ceratocystis albifundus on native South African trees

Abstract: Summary Ceratocystis albifundus causes the disease known as wattle wilt of non-native Acacia mearnsii trees in South Africa, Uganda and Kenya. Infection results in rapid wilt and death of susceptible trees and stem cankers on more tolerant trees. It has been suggested that C. albifundus is indigenous to southern Africa, possibly having spread from native Protea spp. to non-native A. mearnsii and A. decurrens trees. Although C. albifundus has been collected from Protea spp., these reports are based on limited records for which only aged herbarium specimens exist. During surveys of wound-infecting fungi on native tree species in South Africa, a fungus resembling C. albifundus was collected from Protea gaguedi, Acacia caffra, Burkea africana, Combretum molle, C. zeyheri, Faurea saligna, Ochna pulchra, Ozoroa paniculosa and Terminalia sericea. The identity of the fungus was confirmed as C. albifundus, using comparisons of DNA sequence data for the ITS and 5.8S gene of the rRNA operon. In pathogenicity trials, lesions were produced on C. molle and A. caffra, with some trees beginning to die at the termination of the experiment. This study represents the first report of C. albifundus from native tree species in South Africa and provides unequivocal evidence that the fungus occurs naturally on native Protea spp. The wide host range of C. albifundus, as well as its abundance on these indigenous hosts lends further support to the view that it is a native African pathogen.

Multiple gene genealogies reveal important relationships between species of Phaeophleospora infecting Eucalyptus leaves

Abstract: The majority of Eucalyptus species are native to Australia, but worldwide there are over 3 million ha of exotic plantations, especially in the tropics and subtropics. Of the numerous known leaf diseases, three species of Phaeophleospora can cause severe defoliation of young Eucalyptus; Phaeophleospora destructans, Phaeophleospora eucalypti and Phaeophleospora epicoccoides. Phaeophleospora destructans has a major impact on seedling survival in Asia and has not, as yet, been found in Australia where it is considered a serious threat to the biosecurity of native eucalypts. It can be difficult to distinguish Phaeophleospora species based on symptoms and micromorphology and an unequivocal diagnostic tool for quarantine purposes would be useful. In this study, a multiple gene genealogy of these Phaeophleospora species and designed specific primers has been constructed to detect their presence from leaf samples. The phylogenetic position of these Phaeophleospora species within Mycosphaerella was established. They are closely related to each other and to other important Eucalyptus pathogens, Mycosphaerella nubilosa, Mycosphaerella cryptica and Colletogloeopsis zuluensis. The specific primers developed can now be used for diagnostic and screening purposes within Australia.

Kirramyces viscidus sp. nov., a new eucalypt pathogen from tropical Australia closely related to the serious leaf pathogen, Kirramyces destructans

Abstract: Kirramyces destructans is a serious pathogen causing a leaf, bud and shoot blight disease of Eucalyptus plantations in the subtropics and tropics of South-East Asia. During surveillance of eucalypt taxa trials in northern Queensland, symptoms resembling those of K. destructans were observed on Eucalyptus grandis and E. grandis × E. camaldulensis. Phylogenetic and morphological studies revealed that the Kirramyces sp. associated with these symptoms represents a new taxon described here as K. viscidus sp. nov., which is closely related to K. destructans. Plantation assessments revealed that while E. grandis from the Copperload provenance, collected in northern Queensland, recovered from disease, E. grandis × E. camaldulensis hybrids from South America were highly susceptible to infection by K. viscidus and are not recommended for planting in northern Queensland. Preliminary results suggest the fungus probably originates from Australia. K. viscidus is closely related to K. destructans and causes a disease with similar symptoms, suggesting that it could seriously damage Australian eucalypt plantations, especially those planted off-site.

New species of Mycosphaerella from Myrtaceae in plantations and native forests in eastern Australia.

Abstract: The majority of Mycosphaerella species from eucalypts (Eucalyptus, Corymbia and Angophora) in Australia have been recorded only from trees growing in plantations. This illustrates a bias in research in the past two decades toward commercial enterprise, and it emphasises a lack of understanding of the occurrence of these important fungi under natural conditions. Surveys of foliar fungi in native forests in eastern Australia, as well as adjacent plantations, thus have been initiated in recent years. In this study we describe four new species of Mycosphaerella from Eucalyptus spp. as well as other Myrtaceae. Mycosphaerella tumulosa sp. nov. (anamorph: Pseudocercospora sp.) was found on more than seven species of Eucalyptus and Corymbia in native forests and plantations in northeastern New South Wales and southeastern Queensland and appears to be relatively common, although not damaging to these trees. Mycosphaerella multiseptata sp. nov. was recorded from several locations on species of Angophora in native forests and amenity plantings. Mycosphaerella pseudovespa sp. nov. was found in one location in native forest on E. biturbinata. The first species of Mycosphaerella to be described from Syncarpia, M. syncarpiae sp. nov., was found in native forests in numerous locations from Sydney through to northeastern New South Wales and appears to be relatively common.

Ceratocystis atrox sp. nov. associated with Phoracantha acanthocera infestations on Eucalyptus grandis in Australia

Abstract: Ceratocystis spp. include important pathogens of trees as well as apparently saprophytic species. Four species have been recorded on Eucalyptus grandis in Australia, of which only one, C. pirilliformis Barnes and M.J. Wingf., is known to be pathogenic. A recent survey of pests and diseases of Eucalyptus trees in northern Queensland revealed a species of Ceratocystis associated with the tunnels made by the aggressive wood-boring insect Phoracantha acanthocera (Macleay) (Cerambicydae: Coleoptera). The aim of the present study was to identify the fungus based on morphological characteristics and comparisons of DNA sequence data for three gene regions. The fungus peripherally resembles C. fimbriata Ell. and Halst. but differs from this species most obviously by having much darker mycelium, longer ascomatal necks, segmented hyphae and an absence of aleuroconidia. Comparisons of combined sequence data confirmed that the Ceratocystis sp. from P. acanthocera represents an undescribed taxon, which is provided with the name Ceratocystis atrox sp. nov. C. atrox appears to have a close relationship with P. acanthocera, although its role in the biology of the insect is unknown and its pathogenicity has not been considered.

Fungus gnats and other Diptera in South African forestry nurseries and their possible association with the pitch canker fungus

Abstract: Fusarium circinatum is the causal agent of a serious disease of seedlings in South African pine nurseries. Insects, especially fungus gnats (Diptera: Sciaridae, Mycetophlidae), are suspected of transmitting this fungus in nurseries. The aim of this study was to ascertain which species of gnats are present in South African pine nurseries, and to consider whether these and other Diptera carry F. circinatum. Dipteran fauna were surveyed in four major forestry nurseries between 2000 and 2001. Fungi were isolated from these flies and the resulting Fusarium species were identified. Bradysia difformis was the only fungus gnat species found and it occurred in all nurseries. Other Dipteran families collected included Agromyzidae, Cecidomyiidae, Chircnomidae, Ephydridae, Muscidae, Simulidae and Tachinidae. This is the first report of B. difformis in South Africa. Fusarium circinatum was not isolated from any of the Diptera collected. Fusarium oxysporum and F. stilboides were isolated from Chironomidae, but these fungi are not considered important pathogens in the nurseries surveyed.

Molecular detection of fungi carried by Bradysia difformis (Sciaridae: Diptera) in South African forestry nurseries

Abstract: Bradysia difformis (Sciaridae: Diptera) has recently been identified from South African forestry nurseries, and is thought to have been introduced into the country. Fungus gnats, including Bradysia spp., are known to transmit various fungal pathogens. It has thus been hypothesised that B. difformis might be responsible for the rapid spread of the pathogen Fusarium circinatum within South African forestry nurseries. Previous studies have, however, failed to confirm this assumption. In this study we attempted to determine the association between B. difformis and the two nursery pathogens F. circinatum and Botrytis cinerea, using sensitive DNA-based markers. A total of 60 fungus gnats and four combined collections of 25–30 fungus gnats were obtained from four of the major forestry nurseries in South Africa. The species-specific primers CIRC1A and CIRC4A and C729+ and C729– were used in an attempt to detect F. circinatum and Bo. cinerea, respectively. The sensitivity of these primers when fungal DNA was mixed...

The eucalypt leaf blight pathogen Kirramyces destructans discovered in Australia

Abstract: Kirramyces destructans is a serious pathogen causing a leaf, bud and shoot blight disease of Eucalyptus species in plantations of the subtropics and tropics of South East Asia. This pathogen was first discovered in Indonesia in 1995 and has subsequently spread to Thailand, China and Vietnam. Kirramyces destructans is not known to occur in Australia and has been considered a major biosecurity threat. During the course of the past four years, surveys have been conducted in existing eucalypt trials in tropical Australia. Several Kirramyces spp. were detected in these surveys, including isolates with morphological and cultural characteristics resembling those of K. destructans. In this study, DNA sequences of three gene regions were used to compare isolates of Kirramyces spp. emerging from the surveys and these were compared with those of K. destructans and the closely related K. eucalypti and K. viscidus. Results have shown, for the first time, that K. destructans is present in northern Australia (Melville Island, Northern Territory and Derby, Western Australia). The observed sequence variation among a small number of isolates also strongly suggests K. destructans is endemic to Northern Australia.

Seiridium cardinale on Juniperus species in Greece

Abstract: Summary Seiridium cardinale, the cause of cypress canker disease, was found on Juniperus foetidissima, J. excelsa, J. oxycedrus and J. phoenicea, in a number of natural juniper woodlands in Greece. The presence of infections was sporadic in most cases, with a limited number of plants affected by the pathogen. At one locality in the Prespes Lakes region of northern Greece, however, the incidence of infection was very high, especially on J. foetidissima and J. excelsa. The identity of S. cardinale was confirmed using morphological characters and comparisons of DNA sequences for the b-tubulin gene region. The pathogenicity of S. cardinale isolates from Juniperus and Cupressus was verified in cross-inoculation trials on both potted and field grown plants.

Genetic diversity of Chrysoporthe cubensis in eastern and southern Africa

Abstract: 9,14 Chrysoporthe cubensis is an important fungal pathogen of Eucalyp- tus 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 coun- tries. Population diversity studies were conducted using five pairs of microsatellite markers previously developed for Chr. cubensis. Results show that there is a very low genetic diversity within the populations of Chr. cubensis from Kenya, Malawi and Mozambique, implying that the fungus was probably recently introduced in these countries. Based on phylogenetic analyses, the origin of East African Chr. cubensis is most likely Asia.

Characterization of the pitch canker fungus, Fusarium circinatum, from Chile

Abstract: Fusarium circinatum is the causal agent of the pine disease commonly referred to as pitch canker. During 2001, a Fusarium species was isolated from dying Pinus radiata clonal hedges in various forestry nurseries in Chile and was subsequently identified as F. circinatum. The aim of the study reported here was to provide a detailed characterization of Chilean isolates of the fungus. Morphological characters included microconidia carried on false heads and produced on polyphialides. Sterile coils and conidiophores on erect aerial mycelium were evident on synthetic, low nutrient agar. Furthermore, perithecia exuding viable ascospores were produced when isolates were crossed in all possible combinations with the mating tester strains representing the H mating population of Gibberella fujikuroi species complex. PCR-RFLP analysis of the histone H3 gene region, routinely used to distinguish between members of the G. fujikuroi complex, further confirmed the identification of the isolates as F. circinatum. DNA sequence data obtained for the same gene region placed the isolates within a well-characterized G. circinata clade. These studies provide unequivocal evidence that the pitch canker pathogen is well established on pines in Chilean nurseries.

Sirococcus shoot blight on Picea spinulosa in Bhutan

Abstract: We thank the Conifer Research and Training Partnership (CORET, http://woek.boku.ac.at/coret/), funded by the Austrian Development Co-operation (Austrian Ministry of Foreign Affairs) and the Royal Government of Bhutan for the opportunity and partial funding to undertake this study.

Holocryphia eucalypti on Tibouchina urvilleana in Australia

Abstract: Tibouchina spp. (Melastomataceae) are native to South America, but have been planted as ornamentals in many southern hemisphere countries. The Melastomataceae are members of the Myrtales and are close relatives of the Myrtaceae, to which the genus Eucalyptus belongs. The recent discovery of several Chrysoporthe spp. on Tibouchina spp. has prompted a more detailed survey for other Eucalyptus pathogens that might occur on this tree. In this study, the discovery in Australia of Holocryphia eucalypti, a Eucalyptus pathogen, on diseased stems of Tibouchina urvilleana is reported. Characterisation of this fungus was based on morphology and comparisons of β-tubulin gene sequences. Greenhouse pathogenicity tests, including isolates of H. eucalypti from Eucalyptus spp. in Australia and South Africa, showed that the isolates of H. eucalypti from T. urvilleana were significantly more pathogenic on T. urvilleana than isolates from Eucalyptus.