BSPP News Autumn 2001 - Online Edition

The Newsletter of the British Society for Plant Pathology
Number 40, Autumn 2001 

International Sclerotinia Workshop

Central Science Laboratory, York : 8 - 12 July 2001 

This Sclerotinia workshop was the first to be held outside North America. There was a split campus arrangement, with accommodation provided at the University of York, and the talks and posters at the Central Science Laboratory (CSL). This provided the benefit of being near York, and the opportunities to experience a city with over 2000 years of history, and that of a modern laboratory with excellent conference facilities. Approximately 90 delegates attended, the majority from North America and Europe. The programme covered four scientific themes: biology, taxonomy and molecular biology; chemical, cultural and biological control; resistance; and pathology and epidemiology.

The workshop began on Monday morning with an introduction and welcome by Nigel Hardwick, the chairman of the local organising committee, and was followed by the first session of the day on the theme 'biology, taxonomy and molecular biology'. Professor Linda Kohn (Canada) gave the keynote address, providing an overview of the use of two independent genotyping systems, mycelial incompatability groups (MCGs) and DNA fingerprinting, to compare genetic diversity in Sclerotinia populations. Charles Lane (UK) reported on the first official European record of Ciborinia camelliae on camellia, an EU quarantine-listed pathogen in the Sclerotiniaceae. The pathogen, which causes flower blight, was identified for the first time in the UK in 1999 and has since been reported in France, Portugal, Spain and Switzerland.

After lunch, a tour of the Central Science Laboratory's crop health facilities was organised. Using an extensive range of serological and molecular techniques, allied with more traditional methods of diagnosis, the diagnosticians are able to provide an accurate and high quality service. The rest of the afternoon was devoted to the poster session, with a wide range of high quality posters. 

Biological control, using Coniothyrium minitans, featured heavily in both the oral and poster sessions, reflecting the major advances that have been made with this antagonist. Professor John Whipps (UK), a C. minitans 'guru', started the session on Tuesday morning summarising his recent research on molecular characterisation, inoculum quality produced by solid-state fermentation and integrated control of S. slerotiorum on lettuce. It was exciting to learn that integrated control of S. sclerotiorum using soil applications of C. minitans and reduced foliar applications of fungicide was feasible, and did not require a fungicide-tolerant strain. Both oral and poster presentations by Peter Lüth (Germany) provided a review on the current and future status of Contans WG, a commercial biocontrol product containing conidia of C. minitans. The product, available in Germany, the USA, Austria, Poland, Luxembourg and France, can be used to control S. sclerotiorum on a number of field crops (e.g. oilseed rape), but it has to be applied at least 2-3 months before cropping to obtain good disease control. Use of the product to control S. minor and Sclerotiorum cepivorum is currently under investigation. It was predicted that Contans WG would become the most sold biocontrol product world-wide.

My presentation on integrated control of Sclerotinia disease in field-grown lettuce highlighted the importance of 'breaking' the life-cycle of S. sclerotiorum at three key stages by implementing a number of strategies. Recommendations for disease control included: consider using the soil-applied fertiliser calcium cyanamide to reduce sclerotial germination and subsequent apothecial production; use a soil-applied fungicide (e.g. quintozene while still available) in combination with fungicide sprays to prevent ascospore infection; reduce numbers of sclerotia returned to soil by applying effective post-harvest desiccants to crop debris. It was emphasised that these strategies could be used on a number of crops. Christian Martin (France) described the integrated control of Sclerotinia on protected salad crops by solarization and green manuring. Research on the use of these cultural methods for disease control is likely to increase in view of the increasing demand for organically-grown produce. He described fungicide resistance, and the potential of using fluazinam to control Sclerotinia in field crops, such as bean, potato and peanut. There was considerable discussion on sprayer operator safety as the fungicide is a known skin sensitizer. A number of poster presentations identified novel methods of controlling Sclerotinia, including the application of sucrose polyester coatings to pome fruits, and the use of acetylsalicyclic acid.

On Tuesday afternoon, delegates were taken on a coach excursion across the North Yorkshire Moors National Park to the historic and picturesque seaside town of Whitby, providing an opportunity to catch up with 'Sclerotinia' friends and meet new ones attending the workshop. Some delegates were energetic enough to climb the 199 steps leading to the parish church of St Mary, whose graveyard inspired Bram Stoker to include it in his novel 'Dracula'. 

In the evening, a medieval banquet was held at St. William's College, a 15th century building situated in a quiet corner of the city next to York Minster. 

Wednesday morning saw some bleary-eyed delegates challenged by a session on resistance, chaired and encouraged by Jim Steadman (USA), one of the pioneers who initiated and organised the earlier workshops. Presentations described the identification and mapping of molecular markers and quantitative trait loci (QTLs) for resistance to S. sclerotiorum in bean, soybean and peanut. There were some interesting posters describing induced resistance to Sclerotinia. For example, lactofen was shown to induce multiple defence mechanisms in soybean, including a massive induction of isoflavone aglycones, predominantly the 5-deoxyisoflavones, daidzein and formononetin.

Workshop sessions on the theme 'pathology and epidemiology of Sclerotinia' occupied the last day. Several presentations reviewed the epidemiology, forecasting and management of Sclerotinia on oilseed rape. Alastair McCartney (UK) described a polymerase chain reaction (PCR)-based assay for the detection of S. sclerotiorum ascospores in air samples and oilseed rape petals. The development of this PCR assay into a cost effective, rapid and user-friendly technique for early detection of the pathogen is likely to have a major impact on optimising the timing of fungicide application. In the afternoon, a number of presentations reviewed recent research on the epidemiology of S. sclerotiorum on lettuce and carrots. John Clarkson's (UK) findings revealed that ascospore survival was much greater than that found previously by workers in the USA, and may explain why diseased lettuce is often observed in the absence of suitable preceding conditions for apothecial production or ascospore infection. There was an inability to determine a clear relationship between lettuce leaf wetness or relative humidity duration and infection, and further work was proposed to examine this phenomenon before a suitable disease prediction model can be made. The final presentation by Graeme Bourdôt (New Zealand) on risk analysis of S. sclerotiorum for pasture weed control of the thistle Cirsium arvense was rather extraordinary as most plant pathologists concentrate all their effort in controlling Sclerotinia.

There was a lot of stimulating discussion at the workshop, both in the formal sessions and, especially, outside them. I gained a lot of new information on all aspects of Sclerotinia, which will be useful for developing my research further and providing advice on integrated control. I also made useful contacts with Sclerotinia researchers from around the world. 

Many thanks were due to our hosts at CSL, and the organisers, Nigel Hardwick and his committee, for providing an excellent workshop. I thank the BSPP for the travel award that enabled me to participate in and present research at this memorable workshop, and I look forward to attending the next one.

Mark McQuilken
Scottish Agricultural College, Ayr Campus

In Professor Linda Kohn's keynote address on genotypic diversity in Sclerotinia, she showed that genotypic studies can be carried out through more traditional methods in petri plates to determine mycelial compatibility groups, but there are advantages in DNA fingerprinting and microsatellite markers. With these newer methods there is a greater possibility of comparing the genetic structure of the species in different parts of the world. I was interested to find that in spite of forming apothecia, the Sclerotinia sclerotiorum population in a field seems to be made up normally by a few predominant clones combined with several uncommon ones. As different cultivars of a crop may respond differently to different genotypes, it makes sense to study the local population and identify and use the most common genotypes in epidemiological and management studies, in particular in resistance screening.

Among biocontrol agents being developed, Coniothyrium minitans seems to be most advanced, having a German commercial product registered in seven different countries, but other fungi and bacteria are also being studied. Among these, various species of Bacillus are capable of degrading sclerotia, although they probably work with other antagonists in nature. Odile Carisse's presentation on Microsphaeropsis ochracea showed an unusual route to selection of biocontrol agents.  This fungus was originally selected for apple scab control, and has now been shown to reduce sclerotium viability. Martinson and del Rio's poster presented data on the residual disease control due to Sporidesmium sclerotivorum applied to the soil five years before. Other papers addressed the use of various species of Trichoderma in India and Argentina. 

In most cases the biocontrol agents are proposed as sclerotial mycoparasites in order to decrease inoculum in soil, but in some cases they have been tried as protectant crop sprays. Dr Greg Boland showed that Epìcoccum nigrum protects New Zealand kiwi flower petals from infection, diminishing future fruit rot. 

The many papers on resistance show that this disease management tool is being actively studied. Dr Phil Miklas' presentation on resistance in common bean showed the difference between avoidance, due to a more upright growth habit and decreased lodging, and physiological resistance. It was intriguing to note that the loci for this resistance is situated close to those identified as conferring resistance to other pathogens such as Xanthomonas campestris pv. phaseoli , Fusarium sp. and bean yellow mosaic virus.

Other researchers' experience in inoculation techniques is very valuable. For example, Volker Hahn showed one used by his group for resistance evaluation on sunflower. They place a disc of mycelium on the tip of the 5th fully-grown leaf and enclose it in a plastic bag to maintain humidity. By measuring the lengths of leaves and petioles and the time when the lesion reached the stem, they can calculate the speed of fungal growth and use this variable to compare cultivars. I will pass this information on to my colleagues who have begun working on Sclerotinia on sunflower in the north of Uruguay.

It was not all work, though. On Tuesday afternoon we went across the Yorkshire moors to Whitby, and walked through the old streets and up the steps to the Abbey ruins. The rain (of course!) held off until we got on the buses to return to York. We should congratulate the organisers on this exceptional control of the weather! In the evening we had a  medieval banquet complete with period music, the Lord and Lady with their guards, a fool and plenty of food. A really memorable evening!

Congratulations to the organisers on a well run Workshop, and thanks to BSPP for financial support. 

Vivienne Gepp
Facultad de Agronomía, Uruguayan University

The XIth International Sclerotinia Workshop had a scientific programme of 28 platform presentations and some 46 posters.  Papers will be placed on the BSPP Web-site in due course.

An afternoon trip was made to Whitby across the North York Moors, enabling our American cousins to see Fylingdales, likely to be involved in the Star Wars initiative, and those from Australia and New Zealand to see where Captain James Cook learned his seamanship.  We returned from Whitby without leaving anyone behind, a major achievement.  In the evening we attended a Mediaeval Banquet in St Williams's College in York.  I was able to inform our North American guests that the building was commissioned 31 years before Columbus found them!

Inevitably there are people to thank for a well run Workshop.  Chief among these were the staff at CSL: Maggi Churchouse for dealing with the registrations and the multitude of requests for information from the delegates, Paul Beales for staffing the registration desk so enthusiastically, Sue Sainty for typing the programme and papers and Mike Cundall for the excellent projection work and for sorting out the delegates' computer projection files.  The papers were edited and the programme finalised by Caroline Young of ADAS and Kelvin Hughes of CSL, Kelvin being a press-ganged member of the Organising Committee who assisted at the last minute while I was away in Leeds on foot and mouth disease duties.  Others on the Organising Committee to thank are John Whipps of HRI and Jim Steadman of the University of Nebraska and Chairman of the ISPP Sclerotinia Committee and not forgetting Mark Hocart, BSPP Programme Secretary. 

Mark's first major meeting as Programme Secretary was a Presidential Meeting in York in 1997.  It is coincidental that his last major meeting was also at York.  Any one who has organised a meeting will know of all the potential problems and the stresses that occur such as, will the delegates and speakers turn up on the right dates and is the venue expecting them?  That is just for the one meeting, to run a string of them over a five-year period is a daunting task.  That Mark, together with all the other events with which he has been involved, still remains so cheerful is a tribute to his enthusiasm for plant pathology and in passing on its delights to others.  I for one wish him well and a less harassed period before some other organisation grabs him.

Financial support came from Blackwells, ISPP and Syngenta for which the organisers are most grateful.

Nigel Hardwick
CSL, York