Local Plant Pathology Meetings Scottish Mycology and Plant Pathology Club This was another lively and interesting meeting of the Club, which was attended by 32 people. It began with a paper by Gareth Hughes (Edinburgh University) on sampling strategies for citrus tristeza virus and its transmission by two aphid species. Using data from Spain, Florida, Costa Rica and the Dominican Republic, two sampling strategies were compared, sampling individual trees (6.7% of total) and bulked (4) samples from 25% of trees. Neil McRoberts from SAC Auchincruive then presented a paper on models of disease progress incorporating spatial variability. The idea of considering epidemics at less than the field level (precision farming) was presented, together with various ideas for modifying existing models to take into account spatial variability (adding a new spatial heterogeneity parameter; combining logistic equations with over dispersed probability distributions and by considering disease at two adjacent levels in a spatial hierarchy, e.g. plants and plots). Janice McNaughton (SAC Edinburgh) presented her work on expression of pathogenicity in parasexual progency of the eyespot fungus. The majority of parasexual progency were not pathogenic, indicating that recombination had disrupted pathogenicity, but novel phenotypes (R-only) and "parasitic", colonisation only forms were obtained. Mary Noble then gave an account ofAleurodiscus amorphus and its representation in drawings by Beatrix Potter. The afternoon began with S Miller from Scottish Crop Research Institute (SCRI) talking about the potential to control potato diseases with elicitors. David Trudgill (SCRI) gave a paper on the paradox of root knot nematodes (Meloidogyne spp) which reproduce by mitotic parthenogenesis; biotrophic pathogens with little variation but enormous host ranges. They were likened at times during the talk to "stealth bombers" and "low flying marvelous Meloidogyne", perhaps a biased reporter here? Jim Deacon and G Saxena (Edinburgh University) gave a paper on encystment and germination of zoospores of Catenaria anguillulae on nematodes. Results were presented on the effect of mood swing and heart beat drugs on zoospores and other organisms (primarily spiders!) and the rationale for motility and docking in microorganisms was discussed. Stephan Helfer (Royal Botanic Garden, Edinburgh) spoke about rust fungi on the Rosaceae, and made a plea for rust specimens, especially of non-commercial plants e.g. Potentilla and Alchemilla. Posters were given by Vince Mulholland (Scottish Agricultural Science Agency) on the use of PCR to discriminate potato cyst nematode at the species level, J Pickup (SASA) on predicting leafroll virus in Scottish seed potatoes and Miriam Zziwa (SAC Edinburgh) on sensitivity of powdery mildew isolates to morpholine fungicides. Finally, the group remembered Roger Wastie, who had devoted much time to organising SMPPC meetings and who died in January. Jane Chard Scottish Agricultural Science Agency
The autumn meeting of the club was held at the Kerr Building (Glasgow University), home of the Division of Environmental and Evolutionary Biology. After morning coffee amidst the marvellous menagerie (mostly stuffed or skeletal, fortunately) the 35 of us were welcomed by Professor Felicity Huntingford, head of the division. The BSPP kindly offered travel funds to invite Professor Mike Jeger from the Department of Ecological Phytopathology, Wageningen Agricultural University. He spoke about the modelling of soilborne biocontrol organisms using a radical energy-based approach, a method more commonly used in animal studies. Growth of Sporidesmium sclerotivorum hyphae was modelled with different concentrations of Sclerotinia sclerotia as a source of energy. Another lively presentation by Neil McRoberts (SAC, Auchincruive) investigated the eyespot and sharp eyespot sampling procedure used by SAC across Scotland at spatial scales from region through to the pairs of quadrats in a field. A plot of the relationship between the proportion of quadrats infected and proportion of plants infected in that field fitted a beta binomial distribution. Such a relationship is useful in yield loss/disease incidence studies by increasing the reliability of disease incidence estimates from a small number of field samples. The ever enthusiastic Roy Watling (Royal Botanical Gardens, Edinburgh) took us on a fantastic tour of the ectomycorhizal species found in Malaysian rainforest. Very few comprehensive surveys have been undertaken and it was particularly interesting to note that the distribution of orders found in these tropical forests was similar to that of temperate forests of Britain. There were many common species but in one survey 79% of samples were classed as new species showing how little we know of these fungi. Modesty prevents me from enthusing about the next talk by David Cooke (SCRI, Dundee). I spoke of our recent molecular analysis of the inter-relationships within the peronosporales on the basis of internal transcribed spacer (ITS) regions of rDNA. In an examination of the Peronospora species found on raspberry and rose, it was seen that levels of sequence similarity suggestP. rubi and P. sparsa are, in fact, con-specific. Interestingly, the peronosporales species examined so far have also proved to be very similar in sequence to many Phytophthora species. We kicked the afternoon off with potato pathology. Rob Clayton (SAC, Aberdeen) discussed his work on seed potao storage, the sampling strategies and how to minimise storage losses due to bacterial and fungal attack. This was aptly followed by a presentation by Beth Hyman (SCRI, Dundee) on the pioneering work on protocols for PCR-based Erwinia detection on potato tubers. Don Clarke (Division of Environmental and Evolutionary Biology, University of Glasgow), on home territory, discussed the complex interactions between host (Senecio) and pathogen (Albugo) in natural systems. Miriam Zziwa (SAC, Edinburgh) spoke to us about her work on the morpholine insensitivity of wheat and barley powdery mildew. She is investigating the effects of fungicide dose reduction on build-up of insensitivity in mildew populations. The control of bracken is a great problem in the UK and the presentation of Doreen Main (Strathclyde University) on formulations and efficacy of the potential mycoherbicide Ascochyta pteridis was met with interest. Some virology to finish with as E Cecchin (Glasgow University) presented the use of Arabidopsis as a quasi-host for the examination of host-pathogen interactions in the tracking down of virulence factors in Cauliflower Mosaic Virus. The BSPP are gratefully acknowledged for their continued support for visiting speakers and, of course, we thank our new SMPPC organiser Fiona Burnett (SAC Edinburgh) for getting together such an interesting programme and the local host (Don Clarke) in Glasgow for his hospitality. David Cooke Scottish Crop Research Institute Cambridge Mycology and Plant Pathology Club Two meetings were held during the Michaelmas Term. On 15 November, Peter Gladders of ADAS Boxworth presented a 20 year review entitled "Controlling winter oilseed rape diseases - we can do better". A consistent approach to monitoring diseases in commercial crops since 1976 was now paying dividends. Seasonal variation in eastern England was largely attributable to variation in autumn rainfall in the case of canker (Leptosphaeria maculans) but to variation in the carry-over of inoculum in the case of light leaf spot (Pyrenopeziza brassicae). Recent MAFF and HGCA-funded experiments with a "wave" design had identified critical periods for disease control and clearly indicated that it was possible to achieve complete disease control. A further breakthrough in 1995 with fungicide timing experiments showed that canker could only be effectively controlled when sprays were used as protectants. The theory now needs to be translated into farm practice as it is clear that fungicides are not being used effectively. Many treatments are being applied too late and disease incidence remains high. The development of forecasting systems and better understanding of fungicide properties now means we can do better. "Rhododendron powdery mildew - Epidemiology and identification studies" was presented by Avice Hall of the University of Hertfordshire on 29 November. Members were treated to an insight into the mysterious world of the rhododendron enthusiast. This disease probably became established as recently as 1977 in the UK. Following disease progress through a range of symptoms and over several years on a perennial host produced many challenges not faced by cereal mildew pathologists. Active development takes place from May to September and appears to be limited by a relatively high temperature requirement. It was some time before members realised that the name of the pathogen had not been used - Microsphaera sp. seems to be the safest option at present. Peter Gladders ADAS, Boxworth
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