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I had the pleasure to attend the 8th International Mycological Conference (IMC8) in Cairns, Australia (20-25 Aug), and the International workshop “The Ophiostomatoid fungi: Expanding Frontiers”, near Brisbane (16-18 Aug). The workshop on the Ophiostomatoid fungi was a very special one for me, as it focussed specifically on the organisms and topics of my own research. I wish to say right at the beginning: The workshop exceeded all my expectations. Wow, what a great meeting it was!
The Ophiostomatoid fungi are a group of morphologically similar, but phylogenetically diverse ascomycetes belonging to the genera Ceratocystis and Ophiostoma (and a few others), as well as related anamorph genera. These fungi include serious pathogens of forest and shade trees and agricultural plants, with Dutch elm disease (caused by Ophiostoma ulmi and O. novo-ulmi) and Oak wilt (caused by C. fagacearum) probably being the best-known examples. Many Ophiostomatoid fungi are economically important agents of blue-stain of conifer wood and timber, referring to dark discoloration of the sapwood caused by these organisms. At least one species related to Ophiostoma (Sporothrix schenckii) is a significant human pathogen. The Ophiostomatoid fungi are also renowned for their symbiotic relationships with bark- and wood-inhabiting insects and other arthropods, particularly bark beetles, longhorn beetles, weevils and mites. They possess excellent morphological adaptations for dispersal by insects. Their teleomorphs are long-necked perithecia with sticky masses of minute, hyaline, one-celled ascospores accumulating on their tops. Spores get easily attached to the bodies of insects, which carry them to new, appropriate habitats. Many of the asexual stages of these fungi also possess long-stalked conidiophores or synnemata bearing droplets of sticky conidia enabling insect dispersal.
The Ophiostoma and Ceratocystis meeting was organised by Michael Wingfield, a forest pathologist and mycologist from the University of Pretoria and Keith Seifert, a mycologist from Agriculture and Agri-Food Canada. In 1990, they organised the first meeting on Ophiostoma and Ceratocystis in Bad Windsheim, Germany. Three years later a book was published in conjunction with the meeting which resulted in sustained interest in the Ophiostomatoid fungi during the following years. In 2006, the time was ripe for a second Ophiostoma and Ceratocystis meeting, to review the progress that has been made since the Bad Windsheim gathering.
In organising the meeting, Mike and Keith were assisted by Adre Drenth (University of Queensland), helping with the local arrangements, and an organising committee chaired by Marelize Van Wyk. They organised the workshop perfectly and also at low costs. Much detail was put in to the preparation of the event. This is exemplified by the fact that each participant left the meeting with three unique accessories: a T-shirt, a hat and a bag (beautified by handicraft of rural South African women), all carrying the workshop logo and the T-shirt also an attractive Ophiostoma and Ceratocystis drawing. The workshop was held on the quiet and beautiful North Stradbroke Island, near Brisbane, off the East coast of Australia. All participants stayed at a beach resort with a long, beautiful sand beach just two minutes away. To me, this island was the perfect place to hold the meeting! The “concentration” of participants at one resort provided increased opportunities of informal contacts outside the scientific sessions. The scientific sessions took place at the Moreton Bay Research Station of the University of Queensland, a 20-minutedrive away the resort.
Altogether, 39 scientists from 13 countries were present, representing most groups actively working on the Ophiostomatoid fungi. The scientific program was spread over two and a half days and consisted of 35 oral presentations and a poster session with 11 posters. The oral presentations were arranged in four sessions entitled “Taxonomy and biodiversity”, “Economic and ecological impacts”, “Insect relations”, and “Frontiers”.
The taxonomy of the Ophiostomatoid fungi has been in disarray for a long time. The session on taxonomy was therefore a good one to start the workshop. At the Bad Windsheim meeting in 1990 the separation of Ophiostoma and Ceratocystis, which have in the past often been considered as synonyms, was still being discussed. Now it is unambiguously accepted that these are phylogenetically only distantly related, despite the morphological similarities of their teleomorph structures. At the meeting in Brisbane several talks reviewed the taxonomy of various entities within the Ophiostomatoid fungi and dealt with the delineation and naming of new lineages, genera and species. New taxonomic sibling species within the Ophiostomatoid fungi. These complexes consist of morphologically indistinguishable, yet phylogenetically and ecologically separate taxa. The taxonomy and biodiversity session was complemented with presentations summarizing knowledge on the occurrence, ecology and importance of Ophiostomatoid fungi in various regions of the world and in unusual habitats (ie in Protea infructescences in South Africa). All these presentations emphasized the diversity of Ophiostomatoid species.
The workshop continued on the next day with the session “Economic and ecological impacts”. As mentioned above, a number of Ophiostomatoid fungi are serious plant pathogens, particularly of forest and shade trees, or cause economic losses to lumber and other wood products. While many disease problems are caused by native species, there are numerous examples of introduced Ophiostomatoid fungi that cause severe epidemics on susceptible hosts in their new environments. The presentations in this session covered a range of topics, including overviews of plant diseases caused by introduced Ophiostomatoid fungi, case studies of introductions, issues related to bluestain as well as the use of albino strains of Ophiostoma species to reduce the amounts of resin in pulpwood and for biological control of blue-stain. Two presentations were particularly interesting. Clive Brasier reported about hybridization of the subspecies of the Dutch elm disease pathogen O. novo ulmi across Europe. Hybrids are now the dominant form of this introduced vascular wilt pathogen in those parts of the continent where the ranges of the subspecies have been overlapping since the 1980s (eg in Italy and the Netherlands). Moreover, subspecies hybrids are at least as fit as the two parents, explaining their common emergence and firm establishment in Europe. Paal Krokene summarized the findings of a long-term international program on the defence systems of conifers against Ceratocystis and Ophostoma species and the bark beetle vectors of these fungi. The various forms of constitutive and inducible defence systems were reviewed and illustrated with brilliant images of histological sections. At the end of his talk Paal honoured Vincent Franceschi (1953-2005), a key researcher and “motor” of the above mentioned research program on conifer defences, who tragically died at a young age.
The final day of the workshop started with the session “Insect relations”. The association of Ophiostomatoid fungi with insects has been known for a very long time. These symbioses have historically been controversially debated as mutualistic, commensalistic or antagonistic. A contemporary view of bark beetle-fungal-associations is that they are highly complex, variable in space and time (eg during different phases of the population dynamics of the insects) and depend on a wide range of biotic and abiotic factors. The talks in this session reflected the complexity and diversity of these associations. One presentation reviewed the role of phoretic mites of bark beetles and showed that they often add even more complexi ty to the interactions between bark beetles, fungi and their host trees. My own talk reviewed the knowledge on Ceratocystis species associated with conifer bark beetles. While numerous Grosmannia and Ophiostoma species are commonly associated with these insects, only five Ceratocystis species are known as intimate fungal associates of conifer bark beetles. All of them are associated with aggressive and extremely damaging insects. Intriguingly, these bark beetle-associated Ceratocystis species are phytopathogenic and capable to kill their host trees. These systems are thus the main models, where a positive effect of the fungi on the beetles is postulated according to the “pathogenicity paradigm”, with the fungi aiding the vectoring beetles to overcome the defence mechanisms of their host trees. The last session, “Frontiers” highlighted contemporary research using sophisticated methods of molecular biology. The talks dealt with genomics (the entire genome of a yet to be selected Ophiostoma species will probably be sequenced by 2008), molecular methods to follow host infection and concurrent host defence reactions, population genetic studies, and transposable elements in genomes of Ophiostoma species. Mauricio Marin from Colombia gave an excellent talk on virus infections in Ophiostoma and Ceratocystis. Mycoviruses belonging to several lineages are commonly found. Some of them decrease the fitness of fungal isolates and cause hypovirulence, for example in Dutch elm disease. They have thus the potential to be used as biocontrol agents, although there is presently no “real-word”, practical example of their successful application.
The wonderful days at North Stradbroke Island passed quickly and thereafter the “Ceratocystis and Ophiostoma family” dispersed again to numerous parts of the world. As after the Bad Windsheim meeting it is planned to assemble and publish a book, which will update and complement the first volume on Ophiostoma and Ceratocystis. I am extremely grateful to Mike Wingfield, Keith Seifert and their team for having organised this great meeting as well as numerous sponsors for their financial support of the workshop. Many thanks also go to the BSPP for supporting my participation at this and the IMC8 in Cairns. Thank you for helping to make this “dream-come-true-experience” to attend the two meetings in “Down Under” possible for me!
Thomas Kirisits Institute of Forest Entomology, Vienna (BOKU), Austria