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Since phytoplasmas were identified about forty years ago, there has been steady progress in research on these pathogens. Though the inability to culture phytoplasma in artificial media has been a limiting factor, collaborative efforts of plant pathologists and entomologists from around the world has resulted in a rapid flow of new findings in recent years. This first working group meeting, which attracted over 200 phytoplasma experts from 42 countries, was aimed at sharing knowledge on new discoveries and also presented an opportunity for closer collaboration among groups from around the world.
The meeting itself was held at the Alma Mater Studiorum, University of Bologna, on the outskirts of the City and had a packed programme of talks over 4 days. Being Italy, the meeting was run with style. Of course we had to be late starting the opening ceremony (by 30 minutes), and we then had to stand for the EU National Anthem, the Italian National Anthem and the University of Bologna Hymn. But the long lunches (with wine) and the conference banquet on the Wednesday evening which included a different Lambrusco with each course (5 courses in all!), made for a hugely enjoyable atmosphere and a highly successful meeting. Among the various aspects of research results discussed, the areas that generated the greatest interest included phytoplasma genomics, phylogeny and characterization. The publication of the complete genome sequences of strains of Onion Yellows and Aster Yellows Witches Broom phytoplasmas, along with reports at the meeting of others that are sequenced but as yet unpublished, formed the basis for very interesting discussions on the absence of several metabolic pathways, which make the pathogen heavily dependent on its host plants. Dr. Shigetou Namba, among others explained that the encoding of very few metabolic functions within the phytoplasma genome implied that phytoplasma consume metabolites from the plants, which may be the cause of the severe symptoms in infected plants.
In the area of classification, Ing-Ming Lee set the tone for deliberations with his presentation on new ways of using DNA-based systems to differentiate phytoplasmas. He explained how the usual classification based on actual RFLP analysis of 16S rDNA has been taken to another level through bioinformatics. The availability of high quality sequence data has made it possible to simulate restriction digestions and to generate virtual RFLP patterns that are consistent with actual patterns. An approach based on this method resulted in an expanded classification scheme in which ten new phytoplasma 16S rRNA groups and numerous sub groups were identified. This has led to construction of the most comprehensive classification system for phytoplasmas to date. The concept of multi-gene sequence analysis to delineate closely related species also featured prominently in the discussions. Several innovative discoveries of the use of ribosomal proteins, secY and secA genes as phylogenetic markers for finer distinctions among phytoplasmas were presented, and appear to hold great prospects in overcoming deficiencies of classification based on the highly conserved 16S rRNA gene.
New findings in other aspects including insect vectors, detections methods, epidemiology and plant””pathogen interactions were also discussed. Amongst the insect transmission talks was an excellent presentation from Phyllis Weintraub, who discussed the use of physical barriers and also the possibility of symbiont-based protection as ways of protecting crops from phytoplasma diseases. In addition, Mike Wilson discussed his current project to produce a handbook of leafhopper and planthopper vectors of plant diseases, which will be an invaluable resource for phytoplasma research. The possibility of seed transmission of phytoplasma was also discussed by us and others who had found similar results for other phytoplasmas in different plant species. Discussions on this possibility called for further research to involve pollen and other parts of the seeds to help in identifying the possible pathway through which phytoplasmas find their way into the embryo.
The great success of this meeting and the interests indicated by participants for the continuation of such a forum in the future prompted general discussions on the possibility of forming a formal and autonomous organisation of phytoplasmologists. Prior to this meeting the International Organisation for Mycoplasmologists (IOM) had been the major working group which related to phytoplasmas. However, the apparent advantages of a group solely dedicated to research on phytoplasmas became clearly evident at the meeting.
The final consensus was that we should continue to reconvene as a working group for the foreseeable future rather than forming a new society, and it is hoped that the next meeting will be in three years time in either Israel or Germany. Many thanks go to the organizers of this excellent meeting, in particular Professor Assunta Bertaccini for her enthusiasm, dedication and incredible hard work in putting the programme and social event together, and making sure everything ran smoothly. We also thank the BSPP for funding our opportunity to attend and present at this meeting.
Joseph Owusu Nipah and Matt Dickinson, University of Nottingham