Nearly 150 scientists from 16 countries attended the symposium. There were nine sessions covering a range of topics, from genomics to field disease management. Each session opened with an invited presentation, providing an overview of recent research and development activities in the relevant areas, and followed by several offered platform presentations. In addition, there were a varying number of posters within each session.
The symposium was opened with two presentations from Bayer CropScience, the main sponsor of this meeting. Dr Schreier provided an overview on development of new fungicides for managing Botrytis diseases, focusing on the mode of actions, fungicide development cycles and resistance management. He pointed out that consumers are now playing more important roles in marketing products than before, which was previously dominated by growers. He also suggested that toxicity tests are probably more stringent than for human medicine. The global economic importance of Botrytis disease was the focus of the next presentation by Dominique Steiger. About 225 million Euros were spent on Botrytis fungicides in 2005; single-site fungicides from eight families accounted for 65% of the total use. China is, by far, the country with the largest Botrytis-fungicides treated area, while France is the country where there is the greatest expenditure on Botrytis-fungicides. As expected, grape is the most important crop for Botrytis fungicides.
Dr Molly Dewey (Oxford University) then provided an excellent introduction on detection and quantification of Botrytis species, focusing on PCR-based methods and monoclonal antibodybased immunoassays. In addition to the use of these methods in research, new technologies are being developed for fast and reliable detection and semiquantitative assays of Botrytis in field samples, such as lateral flow devices. Several oral and poster presentations in this session focused on development and use of specific methods in research and development. For example, one study revealed the considerable extent of variability between isolates in genes related to pathogenecity: gene expression may differ with the isolates that were used to inoculate host plants. Dr Aerts described a new multi-purpose selective media for Botrytis for estimating inoculum strength in glasshouse studies. Tim O’Neill (ADAS, UK) presented a poster on the use of real-time PCR to quantify latent Botrytis in cyclamen, gerbera and poinsettia.
The next session focused on Botrytis biology and genetics. The opening talk by Prof Hahn covered recent discoveries in Botrytis biology using molecular techniques, including spore germination behaviour in relation to host surface characteristics. There were several presentations from INRA, France and Reading University, UK on fungal population genetic structure in relation to geographical regions, host and resistance to fungicides. Overall, there are significant different differences in fungal populations from different regions and hosts although the exact extent of population differentiation varied considerably. Less population differentiation was found in the fungal population with resistance to multiple fungicides. Several other studies speculated that sexual recombination might have taken place in order to explain the observed larger than expected fungal variation. However, very little sexual reproduction has been observed in nature though it is possible to induce sexual reproduction in the laboratory. There were also a few presentations on signaling involved in the infection process by Botrytis, including the overview by Prof. Tudzynski of Germany. One Italian study reported the molecular characterization of dsRNA mycoviruses in Botryotinia fuckeliana.
There were two large sessions: one on ecology and epidemiology, and the other on disease management. Prof Elad opened the former with an invited presentation. Often two types of lesions (restricted and spreading) are observed though the exact causes for them are not well understood. Having reviewed many studies, Prof Elad suggested that restricted lesions may have resulted from infection by a single conidium. Free water is favourable for infection although too long a period of wetness may result in less disease. Furthermore, infection under dry conditions is possible, particularly on flowers. Fungal colonization following infection may depend on relative humidity or presence of free water. He used several examples to illustrate how such knowledge could be used to manage Botrytis in practice. Two presentations demonstrated that host development stages critically influenced the infection by Botrytis; one was for the infection of blackcurrant fruit (Xiangming Xu, UK) and the other was for grape berries (Marc Feraud, INRA, France). In blackcurrant, fruit become less susceptible to infection as they mature, which is the opposite of what is generally observed on strawberry and raspberry fruit. On grapes, the vigour of host growth and nutritional status also affected infection by Botrytis. Prof Wilcox (Cornell University) showed that disease spread among grape bunches was greater in urea-treated than in control vines and that well irrigated plants also resulted in greater disease spread. Two studies from New Zealand and Australia described the research work on developing models predicting Botrytis bunch rot in wine and table grapes. One study demonstrated the importance of adopting standard disease assessment on the basis of plant development in predicting disease development and evaluating predictive models. Several presentations from Prof Shaw’s group (Reading University) described several types of infection on different hosts. In particular, systemic infection was clearly demonstrated in lettuce and primula. Other contributions focused on inoculum sources on roobios (Chris Spies, South Africa), thrips as a vector of Botrytis for grape flower infection (Marlene Jaspers, New Zealand), and bunch rot development in field conditions (Vivienne Gepp, Uruguay).
Prof Waard (Wageningen University) opened the disease management session with a very interesting talk on compounds that provide indirect disease control through inhibition of fungal ATP binding cassette (ABC) transporters, which is important for pathogen virulence. He suggested that modulators of ABC transporters can be used as lead compounds for further development of compounds for indirect disease control. One of the key aspects in Botrytis management is to reduce the rate of strains developing resistance or insensitivities to fungicides. Several presentations reported the presence of field Botrytis isolates that are resistant to multiple fungicides. Such resistance was shown to correlate with overexpression of efflux transport proteins (Kretschmer, Germany), leading to reduced accumulation of fungicides by fungi. Single nucleotide mutations were shown to be responsible for resistance to the hydroxyanilide fenhexamid and to dicarboximides (Agelini, Italy). Several presentations described the extent of fungal resistance in field populations to various fungicides in the USA on apple (Xiao, USA), on grapes in Chile (Esterio) and France (Fillinger) and in Israel on several hosts (Korolev). Similarly, one study demonstrated the potential of the fungus becoming resistant to a specific antibiotic produced by biological control agents (Ajouz, France).
Dr Elmer (HortResearch, New Zealand) provided another keynote speech in the disease management session, focusing on development of integrated disease management strategies for use in practice, particularly on integrating biological control agents and other alternatives to synthetic fungicides. Field trials demonstrated the potential of a biocontrol agent (BotryZen – a formulated product of an Ulocladium oudemasii isolate) integrated with fungicides in effectively managing Botrytis bunch rot in grapes. However, the efficacy of this biocontrol agent depends on the cultivar. Several alternative chemicals were also shown to be very efficacious against Botrytis and powdery mildew on grapes. Several other studies reported the potential of BCAs on strawberry (Cota, Brazil), apple (Duraisamy, Italy) and on tomato (Aerts, Belgium). Fungicides remain an essential component of strategies for successful management of B. cinerea.
As such, several studies focused on how best to use these products in field conditions by understanding their temporal dynamics of effectiveness (Harms, Germany), mode of action (Fillinger, France), effectiveness in reducing geosmins (a volatile compound produced by Penicillum expansum) in vines (Cousin, France), and control efficacy on flowers (Lubbe, South Africa) and roses during postharvest (Morris, USA). In one study, many extracts from medicinal plants were evaluated and a few extracts were shown to be very effective. However, the cost of these medicinal products is far too high to be used in agriculture (Pertot, Italy). Prof Jan van Kan (Wageningen University), described several QTLs responsible for resistance to Botrytis cinerea on tomatoes. Modelling and forecasting disease risks were described for Botrytis on tomatoes (Aerts, Belgium) and vines (Charnay, France). Finally, several presentations described problems and strategies for integrated management of Botrytis on vegetables (Gullino, Italy), roobios (Lamprecht, South Africa), tomato (Aerts, Belgium), lisianthus (Elad, Israel) and grapes (Walter, NZ).
The Botryits “-omics” session followed the ‘disease management’ session. This session was opened with a presentation by Prof Fillinger (INRA, France) on the B. cinerea genome. Her talk focused on general comparisons among three sets of genomic sequences: B. cinerea from France (http://urgi. versailles. inra. fr/ project/Botrytis), and B. cinerea and Sclerotinia sclerotiorum from the Broad Institute (http://www. broad. mit. edu/ annotation/fgi). Current predictions of the three genomes suggested that there are 14000 to 16000 genes for both species, of which more than 50% (ca. 8400) were shared by the two species. Currently much effort is being focused on functional annotation of the genomes, such as mating type loci, genes involved in primary metabolism, stress response, transcription factors, and the early phase of infecting plants. Robin (INRA, France) described gene clusters involved in secondary metabolism of the fungus for sesquiterpenes biosynthesis and its possible contribution to necrotrophic and polyphageous habits. Preliminary results on the secreted proteome from B. cinerea identified about 90 proteins, including cell wall degrading enzymes and proteases (Shah, USA). Similar research was also done to understand the secretome during the early infection phase (Espino, Spain; Cantoral, Spain). Dr Vivier (Stellenbosch University, South Africa) provided experimental evidence suggesting that the mechanism for the fungal inhibition effect by PGIPs is related to the lipoxygenase (LOX) pathway. Several studies focused on understanding host genes involved in the host response to Botrytis infection on tomato (Curvers, Belgium), Arabidopsis (Denby, UK), and tobacco and grapevine (Vivier, SA).
Host-pathogen interactions were the focus of the next session, which was opened with an overview by Jan van Kan. First, he reviewed generic roles of host plants played in the host-pathogen interactions with emphases on reactive oxygen species, senescence, and programmed cell death, host specificity and improving resistance via interfering with cell death. Next, he reviewed plant responses to Botrytis infection, including PGIPs and phytohormonemediated defense pathways. In the same session, Prof Tudzynski (Wilhelms University, Germany) reviewed the pathogen side of the host-pathogen interaction, focusing on pathogenicity determinants. Several presentations then focused on specific aspects of either host or pathogen responses. The final session was an open session on Botrytis management, industry and the food chain; this session was open to people from the farming, agrochemical and food industry and drew a good attendance. Prof Darriet (INRA, France) gave a fascinating talk on the impact of bunch rot complexes on musts and wine off-flavours. Although Botrytis is always present on rotten grape bunches, the wine off-flavours were shown to relate to interactions between B. cinerea and other secondary invaders, particularly species of Penicillum on the production of geosmin. P. expansum synthesizes geosmin in amino-acid deficient grape juice, which was caused by B. cinerea. However, only a minority (5%) of Botrytis strains tested promoted geosmin production (La Guerche, Farnce). Several presentations focused on the control of Botrytis using fungicides: mode of action (Wilcox, USA), fungicide resistance (Walker, France; Kretschmer, Germany), control efficacy (Brink, SA; Petit, France), and their life-cycle management (Lachaise, France). The final 2 oral presentations focused on disease management from an industry perspective.
Molly Dewey, Tim O’Neill, and Xiangming Xu are grateful to BSPP for travel funds. Xiangming also gratefully acknowledges additional funding from the Worshipful Company of Fruiterers.
The next Botrytis meeting will be held in Cadiz, Spain in 2010.
Xiangming Xu, East Malling Research Molly Dewey, Oxford University Tim O’Neill, ADAS