It is difficult to imagine more idyllic work: a tour, beginning in Berkeley, California, and ending in Medford, Oregon, taking in Yosemite National Park, Mammoth Mountain, Lake Tahoe, Lassen Volcanic National Park, Mount Shasta and Crater Lake. Yet it was, in fact, work! I arrived a day early to take advantage of a pre-congress tour of areas in Marin County badly affected by Phytophthora ramorum. This tour, flamboyantly narrated by Matteo Garbelotto, was very enlightening in terms of the peculiar combination of climatic conditions and host susceptibilities that have lead to such devastating ecological consequences.
Sunday afternoon and the whole of Monday were taken up with oral presentations at the well appointed Clark Kerr Campus of the University of California at Berkley. Sessions on these days included Systematics, taxonomy and phylogeography, genomics and plant-pathogen interactions, population genetics and epidemiology. The key to success in these meetings has also been the interspersing of formal presentations with field visits, where the problems being discussed can be observed directly. This approach is rather useful, certainly in the current climate, where some ‘molecular’ plant pathologists may get few opportunities to actually see the disease problems they are addressing in the laboratory.
So, after an evening’s entertainment and feasting in San Francisco’s Chinatown, and at least partial recovery through sleep, we boarded the buses to Yosemite National Park. Being August of course, it was rather busy in the valley, but in such a large expanse of forest, we were able to avoid the crowds. It is interesting that the First Nation North Americans managed this area as grazing for hundreds of years before Europeans invaded, less than 200 years ago. Much of the forest on the valley floor is rather young, therefore. There is, however, plenty of root disease killing the trees: soil conditions are perfect for development of Heterobasidion, and this disease is abundant in many areas, leading to regeneration problems and safety fears. A further day of formal presentations followed, based at the Mammoth Mountain Inn, some 2,500 metres above sea level. The whole morning was taken up by the ecology of root diseases. With the shortage of oxygen at this elevation though, later talks were restricted to 10 minutes in duration. This was an interesting alternative to poster presentations, and enabled speakers to get their message over to the whole conference. Following interesting field visits to forests surrounding Lake Tahoe, with emphasis on the amenity impacts of root diseases, more short presentations were heard at Plumpjack Inn. The following day, we entered Oregon, first seeing serious root disease problems at Lassen National Park, where Heterobasidion is causing considerable problems on amenity sites. Later we saw incredible devastation to mixed ponderosa pine – Douglas fir – white fir stands caused by Armillaria ostoyae (see photograph) near Mount Shasta.
Given suitable conditions, this pathogen, individual genets of which are the largest living organisms known, can kill large numbers of trees and totally change the ecosystem. On the final full day, we were taken to the rim of Crater Lake to view the magnificent caldera. Oh, and many trees on the edge of the crater were affected by Armillaria and dwarf mistletoes. It was sad and somewhat alarming to see the Pinus albicaulis on the crater rim dying from multiple infections by the introduced rust, Cronartium ribicola.
With 6 days already gone, the final morning, included talks focused on new reports and diagnostic methods. The discussions at the end of the conference praised the local organising team for such a marvellous opportunity to hear about and see these fascinating diseases in magnificent settings.
Steve Woodward University of Aberdeen
. . . and a further report on the same meeting
The International Union of Forest Research Organisation’s working party, sponsored by the Koret Foundation of San Francisco was held in Berkeley, California and Medford, Oregon with stops between for presentations and field visits. After surviving the long flight to San Francisco via Minneapolis, it was an early start the next day to join the Pre-Conference Sudden Oak Death Field Trip at the meeting point in Union Square. By coincidence this was also the venue for an “Indonesia Day” complete with oriental dancers, musicians and numerous stalls selling Indonesian crafts and food. As soon as we had untangled ourselves from this jubilation at the very heart of San Francisco we boarded the repro 1950’s bus that took us across the Golden Gate Bridge to the semi-rural Marin County famed for its coastal redwoods. Our first sight of Californian Coast Live Oaks (Quercus agrifolia) killed by Sudden Oak Death (Phytophthora ramorum) was in Lucas Valley (not named after “StarWars” George Lucas who nonethe- less now owns much of it!). We then travelled to a site where some live oaks had been killed by P. ramorum associated with dead tan oaks and Californian laurels whose leaves were heavily infected but survived. Hope for the long-term survival of the tan oak populations which generally grow with the laurel is not high. However many of the less susceptible live oaks should survive. P. ramorum has also been found in several garden centres which sell oriental Rhododendrons, now considered the initial source of infection.
Next day I traveled by BART, the local metro, to the Spanish Colonial Style Clark Kerr campus at the University of California, Berkeley, where we registered for the International Conference on Root and Butt Rots of Forest Trees and were welcomed by our leader Matteo Garbelotto. The first session on systematics, taxonomy and phylogeography covered the three Heterobasidion spp. that are found in Japan as well as the Armillaria spp. found in Norway and Russia. A paper on evolutionary history of Heterobasidion populations in North America was followed by a discussion on their ISGs. Papers were also presented on the molecular characterization of Fusarium spp. and biological control of Fusarium root disease in forest nurseries, and on the relationships among Japanese and European Laetiporus based on phylogenetics and incompatibility tests, assessing the potential invasiveness of Armillaria ostoyae.
On Monday, genomics and plant pathogen interactions were discussed including a novel hypothesis on the nature and ecological implications of pathogen-induced systemic resistance in conifers, monoterpenes as potential markers for relative susceptibility of Sitka spruce to Heterobasidion annosum, and their involvement in cross induction of systemic susceptibility between H. annosum and Diplodia pinea in Italian stone pine. The microarray analysis of conifer tree response to H. annosum at different stages of organ development and disease resistance was presented along with a histochemical and proteomics approach to study the host-pathogen interactions of the douglas-fir-Phellinus sulphurascens pathosystem. The host response to infection by Armillaria ostoyae in Douglas-fir, western hemlock and western red cedar in the southern interior of British Columbia, and molecular studies of H. annosum during colonization of the heartwood and interaction with the reaction zone were also covered along with long-term differences in spread rate of Heterobasidion spp. from clear felled or intact decayed Norway spruce to healthy neighbouring trees.
In the session on genetics and population genetics, the results of sequencing the genome of the forest pathogen H. annosum, population differentiation and colonization history of Armillaria ostoyae in the Landes de Gascogne forest were covered. The session on aetiology and epidemiology also covered H. annosum, its spread in the United States Pacific Northwest Christmas tree plantations and first rotation Larix stands. In addition, losses of Quercus rubra infected by Collybia fusipes in southwest Germany, the importance of rhizomorphs in Armillaria spp. , the influence of soil and silvicultural practices on the distribution of H. annosum inoculum in the Landes de Gascogne forest, the spread of Heterobasidion abietinum in Southern Spanish natural Abies pinsapo ecosystems were discussed along with a study on the correlations between logging processes stem cankers of trees in tropical dipterocarp forests. The procession to the evening meal in Chinatown was preceded by three lions (actually pairs of dancers), drums and gongs to the astonishment and delight of both tourists and residents alike.
The next day, following a field trip in the magnificent Yosemite National Park, we travelled to the Mammoth Mountain Inn nestled at over 2000m above sea level overlooking the high desert and the spectacular Minarets. On the following day, the session on ecology covered an analysis of the Texas oak wilt epidemic and implications for unaffected forest ecosystems, followed by comparative analyses of phenotypic and ecological traits of North American and European isolates of H. annosum, and a survey of fungi on Eucalyptus globulus coppice stumps in western Australia. In addition, there were talks on the presence and frequencies of Armillaria species occurring in the northeastern Alps and the interaction effects between them and Heterobasidion, early infection of Fagus sylvatica by H. annosum sensu stricto and root deformation in young Scots pine stands threatened by root diseases, as well as the evolutionary relationships of a glutathione-Stransferase gene from different intersterility groups of H. annosum sensu lato. This was followed by a field trip to Mammoth Lake and a barbecue at Red Meadow’s Pack Station.
The field trips to Lassen Volcanic National Park and Mount Shasta on the friday concluded at the Red Lion in Medford, Oregon. On the next day the field trip to Crater Lake was followed by a barbecue supper at the Lake of the Woods Lodge. On the final day we heard about new diagnostic methods and their research applications, including the molecular identification of wood rotting fungi in standing trees, gas chromatographic – mass spec investigation of metabolites in the needles and roots of pine seedlings to reveal Armillaria ostoyae infection, evidence of fungi in roots from which fungi could not be cultured, and the detection of Armillaria tabescens by baiting with oak logs and cherry seedlings. Then there was the session on planning and management of stump treatments, trials, disease management and control including the ten-year effects of silvicultural treatments on root disease caused by Armillaria ostoyae in South-central Oregon, infection of Heterobasidion spp. in late precommercial thinnings of Norway spruce in southern Sweden, the colonisation of Norway spruce stumps by Phlebiopsis gigantea, and the influence of different soil preparation and wood debris utilization on Armillaria ostoyae root rot development in Scots pine plantations. During the business meeting there were majorities for widening the topic to trees outside forests. Then it was back to the outside world and return to the UK which was worsened by United Airlines losing my bag – at this point I envied the intrepid pioneers and the native Americans traversing these silent green forests who may have had rapids to face but at least did not have to suffer the frustrations of modern air travel!
Roland Fox, University of Reading
