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8th Meeting of the International Union of Forest Research Organisations (IUFRO) Working Party Phytophthora in forests and natural ecosystems, SaPa, Vietnam 18th – 25th March 2017
In March 2017, around 100 forest Phytophthora researchers from all around the world arrived in Vietnam for the 8th meeting of IUFRO working party 7. 02. 09, ‘Phytophthora in forests and natural ecosystems’. The opening ceremony was held at the Army Guest House in Hanoi with speeches by local dignitaries and a string quartet played classical music as delegates mingled in a reuniting of old friends and colleagues.
A two-day pre-conference field tour started the next morning with the delegation winding northwards among paddy fields and terraced hillsides to SaPa, visiting forest nurseries and plantations of Eucalyptus and Acacia affected by Phytophthora cinnamomi en route. The nursery operations viewed during the tour were less than optimal in terms of Phytophthora management but moves are afoot in the country to educate nursery managers and improve disease management practices.
The conference itself comprised sessions held over four days and started with a series of talks on Phytophthora management and control. Peter Scott, of Scion, New Zealand, demonstrated his modelling approaches to predict global Phytophthora diversity and biosecurity risk. His time series models predict up to four times more Phytophthora species than those currently described.
Peter and his group are also modelling Phytophthora invasiveness traits to predict global risk. This was of particular interest to me as I lead an LWEC Phase 3 project (Phyto-threats; https:// www. forestry. gov. uk/fr/phytothreats) which also involves identifying and ranking global Phytophthora risks to the UK. Given the degree of overlap in the two projects we managed, later in the week, to hold a successful Skype meet- ing between the New Zealand and Australian Phytophthora team and Beth Purse and Louise Barwell, Phyto-threats’ ecological modellers based at CEH, Oxford.
Future meetings are now planned between our two groups to scope out potential areas for collaboration. Giles Hardy from Murdoch University in Australia gave an overview of 25 years of research on management of P. cinnamomi in Western Australia, showing histological evidence for ‘hidden’ survival of the pathogen as hyphal aggregates in non-host, asymptomatic plants. Having been studying for a few years now the survival and spread of P. austrocedri on juniper in Britain, this struck me as a good example of the plasticity of Phytophthoras enabling them to be such successful plant pathogens. Other presentations centered around the problem of Kauri dieback in New Zealand caused by P. agathidicida and highlighted the importance of community engagement in disease management.
Stanley Bellgard of Landcare Research, New Zealand, presented on the ‘Curious Minds’ programme which is aiming to encourage better engagement of school children in science and technology through demonstrating the relevance of science in their lives. Stanley described how the children (“the next generation of Phytophthora researchers”) had designed and developed re-useable bait cassettes to house bait plants in their studies of Phytophthora diversity in local waterways. We had a chance to inspect these bait cassettes which certainly seemed to me a step-up from the mesh bags that we currently use in our own studies!
Other topics included the use of metabarcoding to detect Phytophthora species in soil and water in a range of different ecosystems around the world, including a presentation by my colleague Beatrice Henricot of Forest Research who demonstrated the high diversity of species found at public garden sites in Scotland. It was interesting to see how ubiquitous some Phytophthora species are across different environments, and I believe that as the global picture continues to develop we shall start to see (and hopefully understand) patterns in species distribution and diversity. Importantly, David Cooke of the James Hutton Institute in Scotland highlighted some of the pitfalls of using the multi-copy ITS region for Phytophthora identification, and he described a bioinformatics pipeline developed by his colleagues which takes into account within-species sequence variability when clustering to a species assignation.
Other presentations of particular interest to my work included a talk by Matteo Garbelotto, University of California, on disease ecology of the aerially dispersed P. ramorum which demonstrated a six-week delay between rainfall events and finding of inoculum in rain traps. In terms of Phytophthora management in nurseries, a critical link in the dissemination of Phytophthoras globally, Laura Sims, also of the University of California, presented a nicely contrasting ‘before and after’ study showing how a series of changes to nursery management practice can dramatically reduce Phytophthora detections.
Similarly, Agnes Simamora of the University of Nusa Cendana in Indonesia, showed how P. boodjera infections in a containerised production nursery can be eliminated by steam-sterilising the re-used seedling trays. This evidence to support the positive effects of relatively straightforward management changes will be useful in my own Phytothreats project which is looking at Phytophthora diversity in relation to different management practices across UK nurseries.
Last, but not least, there was an evening session in which Thomas Jung of the Phytophthora Research Centre in the Czech Republic presented several talks on surveys conducted in various parts of the globe looking for centres of origin of Phytophthoras. It was of great interest to the delegation that his surveys have isolated P. ramorum from streams in natural forests in the northern part of Vietnam, close to SaPa, and much discussion focused on whether this might indeed be a source region for the pathogen.
Thomas also described a new sister genus of Phytophthora, provisionally named ‘NothoPhytophthora‘, from soil samples and streams. This is one we shall be looking out for in our own surveys. Overall, this was a very enjoyable meeting which has stimulated research ideas and resulted in new collaborative projects for our group, and I wish to extend my gratitude to the BSPP for providing funding enabling me to attend.
Sarah Green Forest Research Following the success of the 2014 meeting of this IUFRO group in Argentina, it was the turn of Asia and Oceania to host the conference. South East Asia has long been postulated to be the centre of origin for many Phytophthora species, and with their rapidly expanding economy Vietnam is now experiencing many of the problems with Phytophthora as those encountered in other areas of the world. It was thus decided that the 8th occasion of this conference would be held in Vietnam, hosted by the Vietnam Academy of Sciences in association with Murdoch University, Australia.
The conference started with a preconference field trip including stops at sites which displayed the plantation forest industry in Vietnam from seedling selection right through to the use of the trees in paper production. There were 85 presentations given on different aspects of research with Phytophthora, broadly organised into sessions on management, community engagement, diversity, ecology, genetics, surveys and new species, pathways of invasion, isolation and ID, pathogenicity, physiology and resistance. There was also a brainstorming session where many of the attendees shared their ideas of what would be the 50 year impact of our current research, and our 100 year vision for Phytophthora research.
I presented my work on the Phytophthora diversity in trade and nontrade locations in Ireland, as well as a poster on the Phytophthora species richness on the island of Ireland. There were many very interesting presentations given, but for me I was struck by the fact that even though many of these species have been known for a long time, we are still discovering new information about their biology and epidemiology. For example, even though P. cinnamomi was first described in 1922, there is still debate over its probable native range. Frank Arentz provided a combination of biological and epidemiological evidence, in combination with the evidence from plate tectonics and anthropology to postulate that the pathogen has been present in Australia and New Guinea for thousands of years. There were also several presentations on the promises and pitfalls of the curative treatment for Phytophthora infected plants using Phosphite. There has been much recent work in Kauri forests of New Zealand where culturally and ecologically import tree species Agathis australis is being killed by the invasive pathogen P. agathidicida. Ian Horner showed that after stem injections with Phosphite these trees could heal around diseased areas, while the Phosphite was also shown to have a fungicidal effect on the pathogen in-vitro.
Another interesting theme from this meeting, and indeed many of these meetings, is the taxonomy of Phytophthora species. Proposals to name many new Phytophthora species and even one new sister genus (NothoPhytophthora) to Phytophthora were made, while other speakers proposed to revise several current names and hybrids. The opportunities for metabarcoding in assessing Phytophthora diversity was also displayed in several presentations. However, many of the speakers also cautioned about the inherent flaws in these next generation sequencing methods, for example the metabarcoding work of Jean Legeay indicating that sequencing errors may favour the amplification of some taxa over others – with obvious implications for the use of the number of reads as a proxy for taxon abundance.
Overall, this has been another excellent meeting of this group. I am very grateful to the BSPP travel and conference fund, along with the RHS and BMS small grant funds for allowing me to attend, present and network with the leading researchers of the Phytophthora community globally. I look forward to attending the next meeting of this group in Sardinia, Italy in 2019.
Richard O’Hanlon Agri-Food and Biosciences Institute, Northern Ireland Having narrowly missed attending this conference two years ago in Patagonia I was keen to participate and catch up with colleagues on the latest research developments in the field. I was also hit by the extra anticipation that P. ramorum, the cause of the disease known as sudden oak death in USA and also the species that causes epidemics on larches in the UK, had recently been found in Vietnam.
After the field excursion we then made our way to SaPa travelling through busy towns and endless agricultural areas, where it was clear that the growing population, now estimated at over 25 million, is encroaching rapidly on natural forest ecosystems. SaPa is a former French hill resort in the North West of Vietnam. Nearly all the original forest below 1000 m has been replaced by cultivation and secondary scrub growth and the resort is expanding very rapidly with many hotels being built in a haphazard way, and a new cable car is now installed which reaches the top of Mt Fansipan, the highest mountain in Vietnam at 3,143 m. This meeting on Phytophthora, a pathogen that everyone currently acknowledges as increasingly significant in shaping natural ecosystems, was eagerly awaited by the local participants to help them to develop their internal policies on forest protection and management. I hope we achieved this, the future will tell.
I presented two papers, my first paper in the session entitled ‘Diversity’ was on ‘Metabarcoding of Phytophthora communities in Scottish soils’. Metabarcoding using Illumina or other NGS sequencing platforms is increasingly being used by researchers to measure diversity.
Until now the region of choice is ITS but it is now apparent that a better barcode needs to be used for this powerful technique. In my talk I highlighted the ‘pros’ and the ‘cons’ of using the ITS1 as a barcoding region for Phytophthora.
The problem of ITS copy variation within species as well as presence of haplotypes in Phytophthora and the short reads generated by MiSeq are issues in species assignment. The use of two regions (ITS and COX) in the project ‘POnTE’ (www.ponteproject.eu) led by Ana Perez-Sierra (Forest Research) alleviate these problems. I was particularly interested by the talk given by Jonas Oliva (Swedish University of Agricultural Sciences) who uses a novel throughput sequencing method SMRT or single molecule real time. This technique allows longer reads to be sequenced and therefore is much more accurate for species identification. Metagenomic studies have great potential in measuring diversity. In my study, eight Phytophthora species can sometimes be found around symptomless trees raising question about their role in the soil. I also found some new especies, yet to be isolated but also present in other countries. The concept of non-culturable Phytophthora species is now accepted by several laboratories.
My second talk in the session entitled ‘Genetics’ was on P. austrocedri, a species associated with forest epidemics on Cupressaceae in Argentina and Britain.
Both populations (UK and Argentina) are clonal but the number of heterozygous sites and shared characters showed that recombination has occurred between the populations and therefore both populations have a common origin. Finding the origin of Phytophthora species and looking at Phytophthora diversity in natural ecosystems is at the core of the work of Thomas Jung. With his new Phytophthora Research Centre in Brno (Czech Republic), he and his team will now assess the risk these new species pose if introduced in other areas of the world. The proceedings for each IUFRO Phytophtora meeting can be found at http://forestPhytophthoras. org/ proceedings
Beatrice Henricot Forest Research
