BSPP News Spring 1998 - Online EditionThe Newsletter of the British Society for Plant Pathology
Number 32, Spring 1998
Reports of Recent Conferences (continued)
7th International Rubus-Ribes Symposium
and other visits, Australia and New Zealand, January 1998
I left behind a very windy and chilly London on New Year's Day and arrived in Christchurch on the afternoon of the 3rd to a very exceptional 36oC. Fortunately, the following days were a little cooler as our party spent two days visiting cane and bush fruit growers in the surrounding Canterbury Plain. Much of the labour employed in fruit picking comes from Samoa. At one site the grower combined black currant production with deer farming. As part of this operation new-grown antlers were removed every 55 days to collect the velvet - a practice not permitted in the UK. The velvet is destined for the Eastern medicine trade.
On blackcurrants the most common UK disease, powdery mildew, is rarely found. Botrytis is also uncommon, leaving the growers only leaf spot to worry about. Another unusual feature concerned "big buds" due to gall mite, which are still green and swollen at harvest, unlike in the UK where the mites migrate much earlier in the season. The boysenberry crop of 3000 tons p.a. is very important in NZ, this hybrid fruit being mechanically harvested for processing and export. Trials were visited where Botrytis control was being examined in relation to infection periods.
Led by Geoff Langford of Lincoln University, the group moved North through the Southern Alps to spend two nights at Nelson. On the way we had a short trek through an area of natural NZ forest, the trees dripping with lichens. In the Canterbury Plain the area was largely grass and scrub when Europeans first arrived, and has been planted mainly with trees from the Northern hemisphere. Much of the mountainous area in the North was planted with Pinus radiata for commercial production, the same trees that are being devastated in parts of California by Fusarium subglutinans at present.
From Nelson we went to the HortResearch Centre at Riwaka where we sampled the results of the blackberry breeding programme. The station also carries out trials on hops and kiwifruit amongst other things. On the second evening we were the appreciative guests of the Nelson Yacht Club. We returned to Christchurch via a new area of wine production near Blenheim, and a sealion colony on the East coast.
By the evening of the 9th January the group had arrived at the Queen's College, Melbourne University for the Symposium, organised by Graeme McGregor of AgVic on behalf of the ISHS. Over the next 7 days we had a mixture of platform sessions, posters and excursions in the vicinity of the city. The main areas of disease concern were Phytophthora root rot of raspberry and Rubus Bushy Dwarf Virus. On the former topic a number of contributions were made from Europe and North America on attempts to alleviate the problem, but a common worry was the dependence of growers all over the world on one group of fungicides, the phenyl-amides, for control. To date there have been no publications reporting resistance, but this can only be a matter of time, as many plantations are treated with soil drenches twice a year. In the UK work is underway on resistance-breaking strains of RBDV; these are said to occur in France and Yugoslavia, but have not been reported from other parts of the world. My contribution to the proceedings was on the value of trapping ascospores as a method of determining the start of a spray programme for the control of powdery mildew in black currants. Most of the papers and posters will form a special edition of Acta Horti-culturae in due course.
The excursions were partly scientific and partly touristic, the latter being a visit to Healesville Sanctuary to acquaint ourselves with Australian wildlife. An ad hoc visit was also made to the Melbourne Cricket Ground one evening to educate some of the Americans in the finer aspects of the sport. New Zealand beat Australia B. Scientific visits were made to the Toolangi Research Station (where all were temporarily relieved of troublesome flies when these migrated rapidly to the barbequed meat) and to the Institute for Horticultural Development at Knoxfield. We also visited a grower's holding at Hoddles Creek, where cane fruit plantations had been carved out of areas of the natural forest.
After the end of the Symposium I returned to IHD Knoxfield on 20th January to attend a workshop, arranged by Mark Whattam of the Quarantine Service, on diseases affecting the quality and productivity of the berry industries in Australia and the UK. The following day I had discussions with various researchers at the Institute, led by Rob Holmes and Peter Merriman, on topics as diverse as the impending demise of methyl bromide, diagnostic techniques, post-harvest pathology and plant quarantine.
The country is changing its policy from one of "Fortress Australia" to risk analysis when considering the implication of the introduction of alien pests and diseases. Recently fire blight had been reported in the botanic gardens in Melbourne and Adelaide, which led to the removal of all host plants from those locations and costly inspections of all pome fruit orchards. The disease is non-indigenous and its presence would seriously affect the export of apples to Japan.
On the 22nd January I moved on to Adelaide where Trevor Wicks of the South Australia Research and Development Institute has been a long standing contact, working on similar projects to my own, on Verticillium wilt in potatoes and fruit diseases. The next day we travelled through the bush northwards to the research station at Loxton in the Riverland area of the State, along the very slow flowing Murray River. Here we discussed mildew control trials on grapes where new fungicides, oils and new sprayer technology were being evaluated. The results could be applicable to UK crops on which I am working, including hops and blackcurrants.
The following day we followed a different route back to Adelaide via the famous vine growing Barossa Valley. Many hectares of vines are being planted in S. Australia at present to cater for increased demand for wine in the Far East. Along the way we stopped at a plaque, erected in 1930, commemorating the explorer Captain Charles Sturt who "in January 1830 near this spot had an exciting experience with Natives"! On this stage of my journey, whilst sampling the produce at a local winery, I witnessed the only rain seen during my month down under - it lasted all of 10 minutes.
Before leaving Adelaide I spent the morning at SARDI discussing potato wilt and being shown a new robotic diagnostic machine capable of using PCR and ELISA and then communicating the result to the Institute computer network. At present this is being evaluated by testing cereal fields for take-all, Rhizoctonia and root knot nematode. Interpretation of the results should be interesting!
My final destination was the NSW Orange Agricultural Institute to meet Les Penrose. Orange is located across the Blue Mountains from Sydney, a 45 minute flight. Here the meetings with researchers centered on top fruit, with fungicide resistance in apple scab and stone fruit brown rot high on the agenda. During my brief stay we drove to Bathurst to see field trials at the field station. It was here that in 1906 a horticulturalist named Woltstenholme first recognised the value of the "Granny Smith" apple. He promptly resigned his post and planted up an orchard of the variety. Earlier still an American nematologist/plant pathologist, Nathan Cobb, worked in the area. He had a round revolving table with up to six microscopes. His assistants would prepare the specimens and mount them whilst he sat in his chair rotating the table to look down each microscope in turn. Do they still made scientists like those two?
I had one day left before my return flight to the UK on 31 January, which I spent in the Blue Mountains at Katoomba, the sight of the steepest incline railway in the world. The views were breath-taking and the nearest I had seen in Australia to the splendour of the South Island of New Zealand. So, leaving behind the Sydney Harbour Bridge and Opera House and temperatures in the past month touching 40oC, I arrived back in England at 0600 on 1 February to a ground frost.
The journey had been long but very rewarding, both scientifically and culturally, with many new friendly contacts made and fresh ideas for future work. Without the very generous support of the BSPP travel fund the visit would have been impossible and I would like to record my thanks for the help given.
Tom Locke, ADAS Worcester
ISTA Mycology Workshop
Ottawa, Ontario (Canada), October 1997
Tests for seed borne pathogens may be carried out for a number of reasons, ranging from quarantine requirements, statutory certification, export certificates or domestic advisory tests. Whatever the purpose, critical decisions can be based on the results of a test. This has meant that very strict procedures must be developed and followed to give the guarantees that end-users require. The intense commercial interest in many tests, particularly on vegetable seeds, has lead to the formation of the International Seed Health Initiative (ISHI), and this organisation has developed joint guidelines with ISTA on the production of working sheets. Three workshop sessions were spent on various aspects of this development.
Firstly, Jim Sheppard presented the guidelines booklet and Jeroen van Bilsen, who was the ISHI representative from Bejo Seeds, used his talk on Alternaria dauci testing as an example of how the new procedures should be followed. There was general agreement that the guidelines represented a major achievement, both for ISTA itself, and as a means of generating the most productive outcome from the ISTA and ISHI operations.
Secondly, Denis McGee described the role of the Working Sheet Editorial Working Group,, which he chairs. Despite its awkward name, its function should be very helpful. Essentially it should accelerate the production of ISTA working sheets once the comparative test phase has been completed, and aid the achievement of a uniform format. The group will also be involved in a reorganisation of the ISTA seed health testing handbook, and will produce a framework by which amendments can be added to working sheets and reference methods can be designated.
Finally, Jim Sheppard outlined the scope of the most difficult area of all, which is the number of working sheets which need review. Many methods have not been revised for 30 years, and while some may remain relatively unchanged, there has been a great deal of progress made in a large number of tests which will need the formal ISTA/ISHI approach before the improvements can be published in a working sheet. A small group was formed which will target the sheets needing review, and a few decisions to produce completely new work sheets for high priority pathogens were made at the meeting.
Quality assurance is now a critical part of seed health testing. Various systems are in use, and Valerie Cockerell described the procedures developed within the Official Seed Testing Station in Scotland. As with any QA system, the paperwork seems daunting at first, but several examples of practical benefits soon dispelled any doubts about the need for QA. An ISTA accreditation system will soon be available for labs carrying out disease and other tests on seed.
Several individual tests and other developments were discussed in detail, with some practical sessions in Jim Sheppard's new seed testing labs. Karin Sperlingsson demonstrated the rapid osmo-blotter test for Pyrenophora species on barley and oats, which is based on a colour change in the exudate from infected seed on a sugar impregnated blotter sheet. The colour change is brought about by spraying with dilute sodium hydroxide. The technique is rapid, and reproducible in some extensive ring tests. The principal disadvantage was that it does not distinguish between P. graminea and P. teres. In the UK, seed treatment decisions are highly dependent on the identification of the relative amounts of these species. However, in Scandinavia, seed treatment can only be applied if seed has been tested, and shown to be diseased, and a rapid thoughput of samples is needed which does not allow the lengthy process of identifying P. graminea to take place.
Mark Holderness described results from programmes of work on rice pathogens, using PCR based techniques to track fungal populations and determine the relevance of seed borne infection. This was a particularly interesting example of the use of new detection methods within projects which have a very applied element. As well as the basic research needed to develop the detection methods, the project involved field trials to determine the relative effects of seed borne and other inoculum on disease development and yield losses.
J P Tewari described some initial results on developing RAPD primers for detecting Alternaria species in brassica seeds, and Rhynchosporium secalis in barley seed. Rhynchosporium infected seed could play an important role in contributing to pathogen variation through the movement of seed between different regions.
Risk assessments on seed testing methods are as much a part of health and safety requirements as any laboratory procedure, and one of the least liked methods in routine use is boiling in lactophenol for loose smut detection in wheat. Jim Sheppard presented a much more user friendly technique, which is currently undergoing some inter-laboratory tests.
My own contribution to the workshop was to review methods for the detection of Leptosphaeria maculans on brassica seed. The current technique involves a blotter test, with the seed being treated with 2,4-D to retard growth. Though 2,4-D can be difficult to obtain now, and may be of variable quality, it appears to be a better way of preventing seedling growth than the alternative freezer blotter method, and it is likely that the 2,4-D method will be used in the comparative tests that are now being planned. One of the main disadvantages of the method is that it does not discriminate between aggressive and non aggressive pathotypes, and valuable seed lots, particularly of vegetable brassica crops, could be discarded unnecessarily if they were only infected with the latter.
There were several other useful demonstrations and discussions and, as someone new to seed pathology, I found that the workshop was an excellent introduction to the subject and to many of the people involved, as well as to the operation of ISTA. We were fortunate that the workshop was held in October, which meant that the "fall" colours were at their best, and that there had been no high winds to bring the leaves down before we arrived. Jim Sheppard organised an excellent afternoon trip for us to Gatineau Park near Ottawa. The leaf colours here were superb, and we were all duly amazed that maple leaves could vary from deep green to yellow and orange and red all at the same time of year.
Jane Thomas, NIAB, Cambridge
7th International Verticillium Symposium
Cape Sounion (Greece), October 1997
In a very full programme, there were three and a half days of paper and poster sessions, three evening roundtable discussions, a day field trip and a half day touristic break. The papers were divided into six subject areas: characterisation of Verticillium through molecular methods and vegetative compatibility groups; epidemiology and microsclerotia; host parasite interactions; control by host resistance; biological control; and control by chemical and cultural practices.
The first day was concerned mainly with variation within and between the plant pathogenic Verticillium species V. alboatrum, V.dahliae, V. tricorpus and within the nomen species V. lecanii. This session began with a review (J. Heale) on diversification and speciation in the genus. A second review, specifically on molecular characterization of Verticillium, was provided by M. Typas.
The important and growing contribution of molecular methods to taxonomic and epidemiological studies in the genus was much in evidence in ten papers (and two posters) one of which stated the convincing case for according species status to the former V. dahliae var. longisporum. Work in Canada on the application of PCR to quantifying V. dahliae in soil and in Germany on using PCR to quantify V. dahliae in infected plants also demonstrated the potential of this technology to practical problems of epidemiology and control. The need for criteria independent of pathogenicity for determining relationships was very clear and exemplified by the finding that a newly discovered strain of V. dahliae in Israel which causes defoliation on cotton is not the same as the cottondefoliating strain which has been present in Spain for more than a decade and appears to have evolved independently. There was an overview (T. Katan) on vegetative compatibility in general and Verticillium in particular and four papers and four posters on this topic. European populations of V. dahliae seem to be dominated by two VCG groups which are also present in North America and in Israel.
In an evening roundtable discussion, the relative merits of the various approaches to understanding variability in Verticillium species wereconsidered. Since the last Symposium, an international reference system for VCGs has emerged, based on the work of Rowe's group in Ohio. By contrast, several, often very different, approaches to assessing variability by molecular techniques have been used, and it was apparent that some standardization would be of considerable benefit to future progress.
For the third session on epidemiology, the Symposium was particularly indebted to the work of Termorshuizen and his group, who contributed five out of seven talks. There was a brief report of the important international exercise on comparing methods of quantifying V. dahliae in soil which had its beginnings at the last Verticillium Symposium. The results showed a clear need for standardisation and cooperation in methods: overall differences from 1 to 80 cfu were found in estimates of the same soils by thirteen different research groups. This topic was given more time in an evening session in which a strategy for future collaboration was mapped out. A related paper covered the influence of plating medium on the morphology of V. dahliae in soil plates and its possible impact on quantification. Other topics covered were the unimportance of conidia compared to airborne microsclerotia and plantborne inoculum in dissemination of V. dahliae; the formation of microsclerotia in plant tissues and their significance in inoculum accumulation and control strategies; and the effects of the fungal antagonists Talaromyces flavus and a Bacillus sp. on micro-sclerotial viability.
The session on hostpathogen interactions and host resistance was opened with a review by Richard Cooper. The reasons were discussed for this once widely studied disease model apparently becoming unfashionable in spite of the wealth of excellent anatomical, physiological and biochemical data and the continuing economic importance of Verticillium diseases. Many new, powerful techniques are now available to make significant advances in understanding how these pathogens interact with their hosts and such advances may lead to new control strategies.
Prospects for disease control by genetic engineering were reviewed by McFadden and were centred on natural host defences and their manipulation, including deployment of genetically modified crops. This aspect was discussed further in a paper on improvement of cotton's tolerance to V. dahliae in Australia using transgenic lines with enhanced glucose oxidase and chitinase. Transformed plants showed reduced stunting from Verticillium but those carrying the oxidase transgene also suffered various deleterious effects. She also described the potential for exploiting the transient expression of avirulence genes (from the cotton pathovar of Xanthomonas campestris) in cotton containing bacterial blight resistance genes as triggers of the host's endogenous defence responses. Successful trials in the USA with potato carrying transgenes were reported during discussions.
Wednesday required a pre-dawn start for a lengthy field excursion. On
the rich, alluvial soils around Livanates, three and a half hours drive
to the NW of Athens on the Euboean Gulf, we saw Verticillium wilt
in eggplant, olive and cotton. Eris Tjamos and colleagues demonstrated
field trials on biological control with two Bacillus spp suspended
in water retaining granules and pressure-injected into the soil around
olive trees in affected areas (see photo). We then drove to Thiva (Thebes),
an important centre in ancient Boeotia from the Mycenean civilisation until
12C BC, through the victory over Sparta (371BC) to the Byzantine era and
the Frankish occupation. Many magnificent artefacts are displayed in the
small but well stocked archaeological museum, including a unique collection
of Mycenean clay sarcophagi. A revelation to many of us was the existence
of "designer" statues with recesses such that you could place the head
of your choice. It was at Thebes that the sphinx posed the riddle to Oedipus.
We were then entertained to lunch at the premises of a local company (Spirou
SA) which provides seeds and seedlings to countries of the Mediterranean,
Middle East and Balkans. One of their interests concerns Verticillium-resistant
varieties and rootstocks; they collaborate with pathologists from the Benaki
Institute, Athens on tomato,
watermelon and cotton..
Session 5 began with a review of biological control strategies for V. dahliae (Tjamos). There were several encouraging reports of the potential of antagonistic fungi (Talaromyces flavus and Tricho-derma spp) and bacteria (Bacillus spp, Serratia plymouthica, and Stenotrophomonas maltophilia) as biocontrol agents for verticillium wilts. The potential of Talaromyces flavus is considered such that it has now been registered as a commercial product in Germany as water dispersible granules containing ascospores. Incorporation of this product into soil increased yield of tomato and oilseed rape. In contributions from Professor Tjamos' group, the selection and evaluation of Gram-positive endorhizosphere bacteria as biocontrol agents was described. Dusting seed potatoes with two selected isolates increased yield by 25% in the field. The bacteria colonised the rhizo-spere and survived in host xylem. Stenotrophomonas maltophilia is an important component of the oilseed rape rhizosphere and in field trials reduced the incidence of Verticillium wilt by 23% and increased yield by 9%; an antifungal lactam and lytic enzymes produced by the bacterium may be important in disease suppression. In one paper an unusual role reversal was reported in the control of Rhizoctonia solani on cotton seedlings by Verticillium tricorpus.
The final session started with a fascinating review by Huisman of the ecology of V. dahliae. He considers it to be an obligate parasite as it shows negligible growth independent of the host, but it is a very effective coloniser of the roots of many species, including nonhosts and some monocots. Studies with speciesspecific, fluorescent antibodies shows that the fungus infects behind the root tip, and colonises the inner cortex. Only around 1 in 4000 infections result in xylem penetration and systemic colonisation. Soil inoculum level is the net result of the rates of formation of microsclerotia, their dispersal from aggregates in decomposing plant tissue and their survival. Modelling these processes leads to the prediction that rotations in excess of six years are required to bring inoculum to below critical levels and that annual rotation results in exposing susceptible crops to maximum inoculum. Crops least colonized were sudangrass, maize and alfalfa which experience has shown are the best rotation crops for controlling Verticillium in potato.
The impending withdrawal of methyl bromide as a soil disinfestant has clearly added impetus to work on controlling wilt diseases by cultural means and there were reports of several important developments in this area. G. Lazarovits reviewed the use of highnitrogen organic amendments, which generate toxic volatiles, especially ammonia, and can give excellent control of a range of fungal pathogens and weeds. However, the rates of application required are so high that this approach may not be economically viable. Inconsistency of effect was also reported with a sudangrass green manure which suppressed Verticillium wilt of potato in Idaho but not in Washington State. It was reported that fresh broccoli residues substantially reduced Verticillium wilt of cauliflower in the Salinas valley in California. A totally different approach to disinfestation without recourse to biocidal chemicals was reported by Termorshuizen in which anaerobic decomposition of added fresh, green residues under virtually impermeable plastic sheet substantially reduced the viability of V. dahliae microsclerotia and of some other pathogens. The killing in this treatment is thought to be by the products of anaerobic decomposition such as organic acids. Trials on alternative fumigants for strawberry production in California were reported: a mix of chloropicrin and telone (70:30) was the most effective and reduced V. dahliae soil populations to undetectable levels. Soil solaris-ation is being used with some success for controlling V. dahliae in established olive orchards in Andalucia.
A touristic half day break took delegates to the Acropolis in Athens, whose beauty and history need no description here. Lord Elgin is, rightly, still berated there while Byron is held in high esteem in spite his graffiti on many of the ancient monuments, including Poseidon's temple at Sounion. The evening was spent in an excellent taverna on the coast road between Athens and Sounion. A delicious meal of calamari and other sea produce was consumed in a convivial atmosphere much enlivened by impromptu folk songs from the Russian and Polish contingent in competition with a local bazouki player: a wonderful evening to remember.
The symposium was highly successful thanks to the steering committee. Thanks are especially due to Prof. Eris Tjamos and his ever helpful and charming team from Athens. They are to be congratulated for arranging a complex itinerary and the perfect weather. The location and number of participants was ideal for discussion which, quite simply, never stopped. The authors of this report would like to acknowledge gratefully awards from the BSPP Travel Fund which contributed to their costs of attending this symposium.
Richard Cooper, University of Bath, and
David Harris, HRI-East Malling
5th International Conference on Plant Diseases
Tours (France), December 1997
The second day included papers on the impact of diseases on yield, forecasting, integrated crop management, risk management and the benefits of control. Various forecasting models were presented such as PRESEPT (Septoria spp of winter wheat) whereby a single triazole spray applied according to the model was sufficient and economically profitable in most cases and was equivalent to or better than the traditional two fungicide programme. The models CLEAN ARBRO and ASPHODEL, which simulate the maturity of ascospores of Phomopsis on sunflower and Venturia on apples, helped to identify optimum fungicide timing. The system POSITIF developed by Rhône Poulenc for distributors to improve fungicide timing in cereals and grapes was based on disease presence, including a 48h diagnostic (PCR) service, and meteorological data. I presented (see below) my poster on the control of Allium white rot (Sclerotium cepivorum) in module-raised onions with fluazinam but this fungicide is not registered in the UK for this use. Its main use in many countries is for the control of potato blight, while it is registered in Holland in spring-sown onions for the control of Botrytis squamosa and in flower bulbs for the control of Botrytis spp.. A late afternoon seminar on problems pertinent to the region (Val de la Loire) discussed mainly Aphanomyces root rot of peas and Pythium of cucumbers in recycled nutrient solution.
The morning of the third day considered advances in fungicide control with details of several new classes of compounds:
Strobilurins - Two compounds for the control of diseases in cereals, peas, sugar beet and sunflowers originating from a similar `natural' source were presented. Azoxystrobin (Zeneca) has systemic (xylem only) broad spectrum properties with activity against the four major groups of plant pathogens, while kresoxin-methyl (BASF) is being developed on its own and in mixtures with fenpropimorph and with epixiconazole. These act on mitochondrial respiration.
Phenoxyquinolines - Quinoxy-fen (DowElanco), for the control of wheat powdery mildew, offers protection on unsprayed areas through absorption following re-distribution of its vapour phase.
Oxazolidinediones - DPX- JE874 (DuPont) has a large spectrum of activity on many crops including grapes, cereals and potatoes, and has particular efficacy on downy mildews, wheat septoria and barley net blotch. DPX-JE874 inhibits spore germination.
Hydroxyanilides - KBR 2738 (Bayer AG) has activity against Botrytis cinerea and Monilia spp. in several crops including grapes and strawberries. Its mode of action (it inhibits germ tube and mycelial growth) differs from other botryticides and no cross resistance has been found.
Spiroketalamines - Spirox-amine (Bayer AG) has been developed for use in cereals and grapes and acts as a sterol biosynthesis inhibitor for the control of powdery mildew and rust in wheat and rust, rhynchosporium and net blotch in barley.
Benzothiadiazoles - Acibenzolar-S-methyl (Novartis) has a unique
mode of action, making plants more resistant to disease by stimulating
their defence mechanisms through systemic acquired resistance (SAR). Acibenzolar-S-methyl
does not exhibit any fungicidal properties per se. The chemi
cal is being initially developed for protection against wheat powdery mildew but there is a possibility of not only controlling other fungi but also viruses and bacteria.
The conference was wholly conducted in French (and not to let the side down I successfully presented my poster in French). It was disappointing that in such an international conference there were no translation facilities available. For the not-so-fluent French speakers (myself included) it was very difficult to follow the presentations given in the plenary sessions and some of the poster sessions. One of the big problems was that there were two concurrent poster sessions held with some in the same room. With so many delegates, it was difficult or even impossible in some of these sessions to cover all the posters with the author present.
The Congress dinner was held in the Hotel de Ville with a splendid Renaissance ceiling to draw inspiration between courses. I sat next to a delegate from Poland and I am now a happy possessor of a 1982 Solidarity badge. Sadly, however, the pin badge craze has diminished in France in recent years.
Wearing my BSPP council hat, I set up a small display in the foyer of the Congress Centre with posters and leaflets to publicise BSPP, MPPOL and ICPP98. All the flyers were taken and MPPOL mouse mats were distributed. It was gratifying that most delegates I spoke to had already received Congress details. I am most grateful to the BSPP and ADAS for funds which enabled me to attend this interesting meeting and I look forward to the next one in three years' time.
John Davies, ADAS, Terrington St Clement
Bunts and Smuts of Wheat in the USAAs a plant pathologist newly-employed as a Pest Risk Analyst at the Central Science Laboratory, early in 1996 my first major task was to assess the risks associated with a new record of Tilletia indica Mitra in the United States of America. This fungus causes a disease known as Karnal bunt of wheat (and other cereals). To cut a very long story short, the Risk Assessment showed that there was indeed a real risk of establishment of the organism should it be introduced into the UK. The risk also extended to the European Union. As a result of this, work, amendments were made to the EU Plant Health Directive and the Plant Health (Great Britain) Order which listed T. indica Mitra as a quarantine pest. Several months after the work was completed I was asked to attend a conference in the USA entitled: `Bunts and Smuts of Wheat: An International Symposium'. The symposium was held at the Sheraton Imperial Hotel and Convention Center, Research Triangle Park, Raleigh, North Carolina from 17-20 August 1997 and was organised principally by the North American Plant Protection Organisation (NAPPO). In addition a visit was made to the U.S. Department of Agriculture (USDA) in Maryland, to liaise with scientists from the Animal and Plant Health Inspection Service (APHIS), Plant Protection and Quarantine (PPQ) and others.
The purpose of my visit was complex. Firstly I wished to gain a greater understanding of both the biology and politics associated with Karnal bunt. I also wanted to gain an understanding of the other two fungal pathogens of wheat under discussion at the symposium, namely Tilletia controversa, the cause of dwarf bunt and Urocystis agropyri the cause of flag smut. In addition, I was prepared to explain the position of the UK and the EU in 1996 in placing T. indica Mitra on the quarantine list, if I was challenged (which I was).
The International Symposium on Smuts and Bunts of Wheat was an interesting mixture of politics and science. Research workers and politicians principally from the USA, Mexico, and India with a few from Canada, Italy (FAO), France (EPPO) and Australia were given the opportunity to speak on all aspects including some of the more controversial issues surrounding the afore-mentioned diseases of quarantine importance of wheat.
Two of the three fungal pathogens of wheat that were listed in the programme were considered in much less detail than T. indica, which is currently a political "hot potato". Much historical coverage of old research was presented on the platform and some drawing together of the subjects of current concern was required. To this end a list of questions for debate had been composed prior to the symposium by one of the members of the organising committee. As the symposium progressed these questions became modified to fit the tone of the meeting. The Breakout Group Leaders (of which I was one) were given the daunting task of addressing some of these far-reaching questions with groups of around 40 delegates from many countries on the final morning of the symposium. Facilitators (non-scientists) were assigned to each Group and while this ensured that the tasks assigned to the Groups were completed (albeit in haste) it also meant that the topics were dealt with superficially. Breakout Group Leaders reported back their findings to the symposium and Dr Van der Graaf from the FAO attempted to draw together some conclusions.
Discussions were held at the end of each of the main symposium sessions in which the debate occasionally became heated because it seemed that the aim of the symposium was to deregulate T. indica. Whilst not in a position to give all the detail relating to the symposium in this article I can conclude that the symposium was a success inasmuch as it has stirred-up the debate over T. indica, and may result in an objective drawing-together of the findings of all of the research workers who have investigated the disease and the pathogen since Karnal bunt was first described in India in 1931. The USDA will be including a summary of the findings from the symposium in the proceedings which are as yet unpublished.
At the end of the symposium I flew up to Washington DC to visit the APHIS headquarters of the USDA in Riverdale, Maryland. The principal topic of discussion at the USDA was the methodology and organisation of personnel involved in Pest Risk Analysis. Introductions and discussions with members of the teams involved both in Commodity Risk Analysis and Organism Risk Analysis were arranged as was a meeting with those involved in developing the methodology for Risk Analysis. Much useful information was obtained in the two days of my visit and many new contacts were made.
In short, the visit was a great success. Throughout my 10 years of employment with the MAFF I have always been told that the secret of success for a Plant Pathologist is to work on a subject that none of your colleagues are involved in. This proved difficult in the early days of my career with ADAS as there were so many pathologists to compete with (not so now!). The finding of Karnal bunt in the USA in 1996 (unbeknown to me at the time) has resulted in several exciting opportunities, of which this visit was one. Hopefully, there are more to come!
Claire Sansford, Central Science Laboratory
Approaches to Improving Disease Resistance to Meet Future Needs: Airborne
Pathogens of Wheat and Barley
Prague (Czech Republic), November 1997
This conference was organised under the auspices of EC COST Action 817 - "Population studies of airborne pathogens on cereals as a means of improving strategies for disease control" - by the Research Institute of Crop Production, Prague. The conference was preceded and succeeded by various and numerous meetings of the tortuous network of groups and sub-groups which comprise COST 817.
The week started inauspiciously as my colleague and I contrived to lose our posters while trying to fathom the Prague public transport system on a quiet Sunday afternoon. Eventually, replacements were flown out, only to be impounded by Czech customs! The conference was held at the Krystal Conference Centre and the nearby Faculty of Sports of the Charles University.
Session 1 - "Relevance of virulence surveys for practical breeders" (are there impractical breeders?!) - was fortunate enough to receive a flying start with a paper from Ravi Singh of CIMMYT who was en route from Mexico to Delhi. He neatly described the history and use of specific and partial (= slow rusting) resistance to the three rusts of wheat. Our NIAB egos then received a boost as Bill Angus of Nickersons Seeds proceeded to tell the world (well, Europe, anyway) of the value of our very own UK Cereal Pathogen Virulence Survey to the plant breeders. This was followed by papers on the use of Swiss and Danish virulence surveys by Gabriele Schachermayr and Mogens Hovmoeller, respectively.
Wednesday began with Session 2 on "Deployment of race specific resistance", chaired by Dr Akos Mesterhazy. Naturally, many of the papers were on use of major gene resistance to control brown and yellow rust of wheat and barley, ably kicked off by Dr Alex Morgounov from Turkey. Prof Jahoor from Denmark described his exciting work on marker-assisted selection for resistance, particularly to powdery mildews; use of such markers would certainly speed up virulence surveys! Dr Renata Hanisova then depressed her Czech plant pathologist colleagues by painting a rather gloomy picture of the failure of specific resistance to contain mildew. However, Bill Thomas of SCRI completed the session on an up-beat note by describing his comprehensive work on gene mapping in barley.
"Breeding strategies for partial resistance" was the subject of Session 3. A recurring theme throughout the conference and the COST meetings was the short-term nature of specific resistance, due to eventual breakdown, and the increasing dependence by "practical breeders" on more durable forms of resistance. The keynote paper was given by Albrecht Meinel from Germany on breeding aspects of durable adult plant resistance in wheat. Amongst all these biotrophs, Gert Kema from Wageningen slipped in a fascinating paper on avirulence and mating types in Mycosphaerella graminicola.
The splendid Conference Buffet Dinner was notable for two varying forms of entertainment: one planned, one not. Firstly, our reeling brains were soothed by the strains of Mozart and Telemann, played by an accomplished local quartet. Secondly, Eckhart Limpert from Switzerland persuaded groups from many countries to sing Frere Jacques in their own language, culminating in the massed choir all singing together(?)! As an antidote to this, glasses of the local "Becherovka" spirit were then imbibed.
The final session on Thursday was on "How to assess level of partial resistance", with Mogens Hovmoeller substituting as Chairman for the rather ill Adrian Newton (NOT related to the previous evening!). The keynote paper was delivered by Rients Niks from Wageningen on partial resistance to barley brown rust. Erik Schwarzbach described work on partial virulence for mlo in the barley mildew population; heavy reliance is placed on this durable resistance throughout Europe, especially in Germany and the UK.
Overall, an excellent conference, benefitting greatly from the presence of the (practical) plant breeders, whose contributions helped us to focus on the end users of our pathology work. But, however good the conference, it is the charm of Prague which remains in my memory: the Old Town Square, the Tyn Church, and the November sunshine on the Vltava river. I would like to acknowledge receipt of a BSPP Travel Award, which partly funded my attendance at this conference.
John Clarkson, NIAB, Cambridge