BSPP News Spring 1999 - Online EditionThe Newsletter of the British Society for Plant Pathology
Number 34, Spring 1999
A Summer in Scotland
I used a great deal of my time in Edinburgh learning principals and methods in nonlinear stochastic modelling, and then applying the techniques to strawberry root disease epidemics. For the latter, I worked with Adrian Newton and Jim Duncan of SCRI who had previously collected very detailed data on the distribution of red stele of strawberries. The red stele data posed a modelling challenge because of the extremely large number of observations and high disease incidence. But, I found that the Gibson model could be applied to these data and the results used to characterize disease spread for a soil-borne pathogen.
I anticipate that two journal articles will directly result from the work started in Edinburgh. Perhaps more importantly, the collaborations formed or solidified this past summer will lead to new research contributions for many years.
An important benefit of the fellowship was the ability to conduct research
in new surroundings and have fun with family and friends on weekends and
after work hours. This was a great way to "charge the batteries", as they
say. Scotland is a wonderful place to spend the
Thanks to the generous support from the BSPP Fellowship Programme, I was able to spend the summer of 1998 in Edinburgh, Scotland, working on the spatio-temporal modelling and analysis of plant disease epidemics. I conducted research with colleagues at Biomathematics and Statistics Scotland (BioSS) and the Institute of Ecology and Resource Management (IERM) of the University of Edinburgh, and developed closer ties to colleagues at the Scottish Crops Research Institute (SCRI) in Dundee.
Because of this wonderful funding programme, I was able to continue
work with my long-term collaborator, Gareth Hughes, on the spatial patterns
of plant diseases, and develop new models for the effects of ecological
scale on observed spatial heterogeneity of disease incidence. I was also
able to make considerable progress on stochastic modelling of epidemics
by working with Gavin Gibson of BioSS. Gavin has developed an elegant method
for fitting stochastic spatio-temporal models to mapped disease data, enabling
researchers to both interpret observed spatial patterns of plant diseases
in fields, and to test the effects of infection rates between neighboring
plants (so-called `local infections') and infection rates attributed to
inoculum in the soil and the surrounding area
summer. My wife and I have always considered Scotland one of our favourite places on earth - due to the beautiful landscapes, castles, and especially the extremely friendly, helpful, and caring Scots - and the summer of 1998 confirmed this opinion. We barely even noticed the frequent rains. Edinburgh is a great city, and we did not come close to exhausting the many things it has to offer. We were able to visit many parts of this wonderful land, checking out agricultural and non-agricultural sites, and I personally made progress on characterizing the spatial distribution of single malt whisky throughout the country. I think considerable additional research may still be needed, however, to adequately study components of this very significant "value-added" barley product. My wife was more interested in the wool sweaters than the whiskey, and our 4-year-old daughter was especially fond of the bagpipers. We are afraid she may become a piper `groupie' when she grows up.
The summer of 1998 will be a professional and personal highlight of my life, thanks to the BSPP Fellowship. I hope that more individuals can participate in this outstanding membership benefit.
Laurence V. Madden, Ohio State University
Fourth International Scientific Meeting, Cassava Biotechnology Network
Salvador, Brazil : 3-7 November 1998
Cassava (Manihot esculenta), a member of the Euphorbiaceae, is a perennial shrub which is propagated using stem-cuttings as a root crop in tropics. Serving as a staple food for 500 million people, the storage root is in fourth place, after rice, sugar cane and maize, in terms of calories provided for human consumption in the tropics. In addition, the roots are used as animal feed and as a raw material for the starch industry.
The symposium was held in the Conference Centre, Trans-American Hotel, Salvador, Brazil. About 110 delegates from 29 countries attended the conference. There were a total of 54 oral presentations, 70 posters and 10 working groups, covering a diverse range of research in cassava: Manihot genetic resources, genome research, genetic transformation, biotic stresses, cassava micropropa-gation, cassava starch, microbial biotechnology for processing, cyanogenesis, farmers' participation in the Cassava Biotechnology Network and gene cloning.
The symposium started with a comprehensive overview of global cassava
production by Dr Guy Henry (CIRAD, France). World production of cassava
has been increasing in recent years and there is a trend for more and more
cassava to be used in industry. Dr R.A. Mendes (CENARGEN/EMBRAPA, Brazil)
presented the research of Dr A.C. Allem's group
on the primary genepool of cassava, which provided further convincing evidence for their hypothesis that cassava was originated from Brazil. Dr B. Schaal (Washington University, St. Louis, USA) provided additional evidence for this hypothesis using molecular phylogenetic analysis. The opening session ended with presentations from Dr W. Fukuda (CNPFM/EMBRAPA, Brazil) and Dr H. Rosling (Karolinska Institute, Sweden), in which the importance of farmer participation in the CBN was discussed.
In the first plenary session, on Manihot genetic resources, and in related posters, the evaluation of Manihot genetic resources and analysis of relationships between genotypes were discussed. The genetic diversity of cassava was assessed using Random Amplified Polymorphic DNA (RAPD) markers or microsatellite-primed PCR markers. A Brazilian collection of cassava was reported which consists of 4100 accessions conserved in five regional Active Germplasm Banks.
The second session, on genome research, described a molecular genetic
map, markers linked to disease resistance genes and marker-aided studies
of complex traits being developed in CIAT (International Centre of Tropical
Agriculture, Colombia). Reactions of four F1 mapping populations to cassava
mosaic disease and cassava bac
terial blight were reported.
Genetic transformation (Session 3) was a hot topic during the conference. At the previous CBN conference (Uganda, 1996), selectable and visible marker genes were transferred into cassava to facilitate the improvement and optimisation of cassava transformation. A lot of progress has been made since then. Dr Nigel Taylor (ILTAB, Scripps Research Institute, USA) reported that transgenic cassava plants expressing the coat protein gene of Common Casssava Mosaic Virus, the AC1 gene and defective interfering (DI) sequence from African Cassava Mosaic Virus and the Xa21 bacterial resistance gene from rice are being produced. The effects of these trans-genic genes on defence by cassava against these pathogens are going to be tested. It is also interesting that ILTAB has been transferring the transformation techniques to developing countries such as Zimbabwe.
Transgenic cassava plants containing Bt genes, hydroxynitrile lyase (HNL) cDNA or the cytokinin biosynthesis gene (ipt) have also been produced to manipulate insect attack, toxicity due to the presence of cyanogenic glyco-sides in storage roots and leaf senescence respectively (Dr P. Chavarriaga, CIAT, Colombia & Dr J. Pounti-Kaerlas; Dr D.I. Arias-Garzon, Ohio State University, USA; Dr J. Pounti-Kaerlas, ETH Zurich, Switzerland).
In Session 4, presentations included the biochemical components of disease resistance of cassava (Dr Richard M. Cooper, University of Bath, UK), DNA polymorphism and virulence variation of Phytophthora populations isolated from cassava (Dr E. Alvarez, CIAT), characterisation of a distinct cassava-infecting gemini-virus from South Africa (Dr M.E.C. Rey, University of Cape Town, South Africa) and the increasing complexity and diversity of the cassava mosaic disease in Africa revealed by its etiology (Dr C.M. Fauquet, ILTAB). Dr Fauquet reported the isolation of two virus strains, African Cassava Mosaic Virus (ACMV) and East African cassava mosaic virus (EACMV), and showed that ACMV was very similar throughout Africa while EACMV revealed the presence of different recombined fragments of known and unknown origins.
In Session 5 and 6, research on micropropagation and cassava starch
was discussed. Commercial propagation laboratories are being established
in Brazil and some other countries. The isolation of a clone producing
much less starch but a lot of sugar was an interesting discovery (Dr L.J.C.B.
Carvalho, CENARGEN). In session 7, isola
tion of amylase-overproducing mutants of Aspergillus niger HPD-2 for amylase production from cassava flour was reported (Dr A.B. Escudero, Mexico), and traditional fermentation of cassava and potential modification or improvement was discussed. In session 8, there was lively discussion of the effect of cyanogenesis on farming and the necessity of genetic manipulation of the toxicity in the storage root. Farmer participatory research was presented in session 9, in which the importance of farmer participation in cassava research especially in breeding programmes was displayed.
In the last session, the emphasis was on the molecular study of post-harvest deterioration of cassava storage root. Dr John R. Beeching (University of Bath) reported the characterisation of genes related to physiological deterioration and Mr Y. Han (University of Bath) presented two posters on the isolation and characterisation of genes encoding phenylalanine ammonia-lyase, beta-1,3-glucanase, hydroxyproline-rich glycoprotein and ACC oxidase in cassava. Mr J. Huang (Wagen-ingen Agricultural University, The Netherlands) presented the results of molecular analysis of the deterioration using cDNA-AFLP. Isolation of storage root specific promoters was also reported.
One of the most exciting events during the conference was the field trip on 5 November. Delegates visited a village (three hours drive from Salvador), where farmers have been carrying out cassava research with Brazilian scientists. The farmers' research was reported and exhibited. Delegates then visited the trial field and two cassava processing factories, which gave a great impression. The farmers treated the delegates with their traditional dishes, fresh fruits and traditional music, which was highly appreciated by all the delegates and many were quite reluctant to leave the party.
The symposium was very intensive, with oral presentations during the day, poster presentations during lunch-time and working groups in the evening. There was a lot of stimulating discussion and it was an enjoyable meeting. The beautiful tropical beach, foods and fruits were brilliant as well. I am grateful for the travel grant from BSPP which enable me to attend and present my research at this important meeting.
Yuanhuai Han, University of Bath
Molecular Biology of Fungal Pathogens IX
"Brumynog" : 15-17 July 1998
In January 1988, around 50 UK researchers interested in the genetics and
molecular biology of fungal pathogens of plants held an informal meeting
in Norwich. This initial meeting has been repeated most years since then
at various sites around the country and the
number of participants has grown to over 100, reflecting the increasing activity in the UK in this area of molecular plant pathology.
The meetings have not been held under the auspices of any Society, although in recent years sponsorship has been obtained from both The British Society for Plant Pathology (BSPP) and The British Mycological Society (BMS), and there are no committees or officers. Rather, the responsibility for organising the next MBFP meeting is passed to a new team of 'volunteers' at each meeting. From the outset the meetings have been generously supported by The Gatsby Charitable Foundation and in recent years further sponsorship has been obtained from AgrEvo UK Ltd, PBI, Unilever and Zeneca Agrochemicals, as well as from BSPP and BMS. Because of this support, it has been possible to subsidise the costs for postgraduate students with the result that the meetings have been characterised by the active participation of these future researchers.
Many former UK postgraduate students in this field gave their first external talk at one of these meetings. The University of Wales Conference Centre at Gregynog has proved to be a popular venue, and the name 'Gregynog' has become associated with the meetings irrespective of where they are held.
The 1998 meeting (MBFP IX) was held at The University of Birmingham ('Brumynog') from 15-17 July and organised by Chris Caten, Jon Green, Sarah Perfect and Simon Cutler. Eighty six people participated, of whom 42 were postgraduate students and many of the rest were young postdocs. This number was rather less than at the previous few meetings, but was pretty good considering the competition of the pending International Congress in Edinburgh. Accommodation was in one of the University residences and the meeting was held on campus about 15 minutes walk away; fortunately the weather was good.
Altogether twenty talks were presented on various aspects of fungal pathogen molecular biology and molecular mechanisms of pathogenesis. In addition, there were three 'complementary' presentations on host responses to fungal infection. Everyone who offered a paper was accommodated and sixteen of the talks were given by students.
Despite (because of?) the relative inexperience of the presenters, all the talks and visual aids were of a very high standard; so much so that some of the 'old stagers' expressed a concern that the meetings are in danger of losing some of the spontaneity and informality of the early gatherings.
In addition to these talks, workshops were held on Fungal Genomics and Bioinformatics, Studying Pathogenicity with Reporter Genes and Approaches to the Study of Biotrophy and Hemibiotrophy.
It is said that "all work and no play makes Jack a dull boy", so the talk of REMI, ESTs, MAbs, transposons, quantitative PCR, apoptosis, etc. was lightened by an inter-lab volleyball tournament. This proved to be a popular and highly competitive event that was won by the team from the John Innes Centre.
There was also a Ceilidh after dinner on the last night, so that the participants returned home having been both intellectually and physically challenged. These social events mix up the groups from different labs and stimulate much constructive discussion of work that goes on by E-mail after the meetings.
The meeting concluded with a business session during which Nick Talbot outlined ongoing discussions within BBSRC about a possible new initiative on plant and animal fungal pathogens, and Sarah Gurr encouraged the postdocs, especially the women, to apply for personal fellowships as the next career development step.
The intention of returning to Gregynog in 1999 was confirmed and the date fixed as 7-9 July. Dave Shaw and Sue Assinder from Bangor will look after the domestic arrangements, and the scientific programme will be organised by Adrian Newton, Paul Birch and David Cooke from SCRI.
Further information about MBFP X can be found at: www.bspp.org.uk/mbfp or by contacting: Dr A C Newton, Scottish Crop Research Institute, Invergowrie, Dundee, DD2 5DA, Scotland; Tel: 01382 562721; Fax: 01382 562426.
Organising meetings without the financial backing of a Society is a risky undertaking and it is only through support from various sponsors that the organisers could sleep at night. We would therefore like to thank AgrEvo UK Ltd, BMS, BSPP, The Gatsby Charitable Foundation and Zeneca Agrochemicals for their generous support. As a result, the meeting not only covered all its costs, despite subsidising student attendance, but yielded a surplus that has been passed onto the organisers of MBFP X.
Chris Caten, Jon Green, Sarah Perfect, Simon Cutler, University of Birmingham
Thought for the day...
A few months in the lab can save you hours of time in the library
Seen in the Genetics Department, University of Cambridge
More on the 7th ICPP, Edinburgh, 1998...!
Dr Eugene Terry, in the Opening Session, emphasised the importance of in-depth
knowledge of ecology of plant diseases and of combining modern biotechnology
and conventional agronomy in research, even though the latter may not seem
strategic. This idea was very well put into practice in the Congress, which
had sessions on themes ranging from molecular biology of pathogenicity
to disease management on resource poor farms.
Whenever possible I attended symposia and meetings on biological control and on disease management using low external inputs, as we are working along these lines in my department. Biological Control was well represented in the Congress, with papers ranging from its ecological basis to its implementation by industry.
On the subject of the ecological basis of biological control, Dr John Whipps gave a very clear keynote lecture on the basis or biological control of fungal diseases, comparing the mode of action of ecologically saprophytic fungi which are non-specific in their action, with ecologically obligate, specific ones, using as examples Giocladium virens (now renamed Trichoderma virens) and Conio-thyrium minitans in their action against Sclerotinia sclerotiorum.
Also in this session, Dr S.E. Lindow gave a good overview of one of the problems in biological control on the leaf surface: the patchiness or aggregated localisation of bacteria on the surface. This, of course, makes it more difficult to get any biocontrol agent to the point where it is needed in order to interact with the pathogen. Among these interactions it seems that nutritional competition for sugars is an important mechanism of biological control. He also showed that immigration of bacteria into crops from neighbouring vegetation can account for much of the diversity in the phyllosphere bacterial population. The rest of the symposium on "The ecological basis of biological control" gave examples of control of different diseases, their successes and difficulties.
The subject was continued in a more informal meeting on "Implementation of Biological Control of Plant Diseases" chaired by Dr Nyckle J. Fokkema. Here I came to the conclusion that one shouldn't follow an orderly succession of laboratory, field, toxicological and formulation studies, but do them all at once, not leaving any until later. Or more exactly, do a bit of everything from the beginning. This is a useful aspect to consider, as some researchers may tend to work with agents which will never be used in crops because of practical problems in industrial production, application or commercialisation. If these recommendations are followed there will be less possibility of continuing costly research on an antagonist which would never be used in the field because it is impractical to produce in large quantities, to formulate and maintain its viability or because it produces toxic metabolites.
On Wednesday there was a very interesting Symposium on "Preventing and controlling disease in systems involving low external costs", in which Prof M.S. Wolfe talked about diversity in the cropping system, pros and cons and different ways of achieving it. I do hope the farming community is really moving away from large expanses of monoculture towards his vision of increased diversity, focus on biological systems and increased employment.
The Symposium continued in the afternoon. I was particularly interested
in Dr Rebecca Nelson's
presentation on "Improving farmer's disease management decisions", as this is relevant to my present work with vegetable growers in Uruguay. The need to work with farmers and to complement or integrate their experience with our scientific knowledge was also emphasised by Dr L. Mughogho, Dr Hilary Warburton and Dr Thurston in the afternoon session. Dr Martha Rosemeyer's presentation was in line with this view, combining the scientific approach of determining the limiting factor, in this case phosphorus, in order to increase yield in the traditional planting system called "frijol tapado" without decreasing its disease and weed prevention effects.
In the evening there was a meeting on "Monilinia of stone and pome fruits", including identification of the different species, epidemiology and genetic and biological methods of control. Dr Charles Lane presented a surprisingly simple, low cost method which only requires a potato dextrose agar medium and incubation facilities, not even a microscope to separate the three species. Other methods being studied for identification to the species level are serology and RAPD-PCR. Latent infections remain a problem because of cross-reaction of substances of the fruit pulp in serological tests and because of the very small amounts of fungus in the fruit. Also, the discovery that often latent infections do not develop in storage complicates matters even more.
In studying the movement of pathogens, we were treated to the effect of dispersal of biocontrol agents by bees, of bacteria by rain splash and movement in soil, and citrus tristeza transmission by different aphid species.
In an evening meeting Dr Ieuan Evans emphatically showed the importance of crop nutrition, both in causing disease symptoms and susceptibility to biotic diseases.
On Tuesday Dr N.D. Paveley gave an excellent talk on the different factors to consider in optimising the decision of when and how much fungicide to use on a crop. Dr J.M.B. Secher then showed the basis of the decision support system used for cereal diseases in the Netherlands.
On Thursday, when I attended the Symposium on "Endophytes", I began
to revise my concept of what pathogens are! At least I started thinking
about the difference between pathogens and non-pathogenic micro-organisms
which live in or on plants, when I learnt about endophytic fungi and bacteria
that normally aren't pathogenic, but in some circumstances may cause disease
in their hosts. Perhaps we should talk about pathogenic phases instead
pathogens! I was very glad I didn't have to teach a group of students beginning a Plant Pathology course at that moment!
In the first set of posters I was impressed by the number of papers on systemic acquired resistance (SAR), many of them financed by chemical companies. Of course this is an indication of their movement towards the use of natural compounds and processes in order to control disease in a way which will probably be more acceptable to the consumer.
I was very well impressed by the excellent organisation of the whole Congress. I have had some experience in the organisation of a Congress for about 200 delegates, and this one had more than 2000! We even have our daily exercise included, going from one session to another, specially if one was held in the Stakis Grosvenor Hotel, about 10 minutes' walk from the rest of the venues. This was taken into account by the Chair of one of the Meetings, who instituted "Gros-venor time", which was 10 minutes later than for the rest.
In a truly international Farewell
Ceilidh, we made up for all the week's sandwiches and evening meals eaten standing up between sessions. It was good to meet other plant pathologists in a more informal atmosphere. The atmosphere got even more informal after dinner, when we were trying to do a little Scottish dancing and getting quite muddled sometimes. The evening ended in true Scottish style, with an impressive bagpipe performance and Auld Lang Syne.
I am very grateful for the possibility the BSPP gave me to attend this excellent Congress, and to meet so many other researchers. I feel that I have been able to return home with a lot of information and contacts useful not only for me but also for the rest of the group I am working with. After the Congress I was also able to visit HRI Wellesbourne and CSL at York, and talk to researchers in a more relaxed atmosphere, not rushing off to listen to a paper or to see posters.
Vivienne Gepp (firstname.lastname@example.org), Catedra de Fitopatologia, Montevideo, Uruguay
Sixth International Mycological Congress
Jerusalem : 23-28 August 1998
The International Convention Centre and Jerusalem Crown Plaza Hotel provided the venue for the Sixth International Mycological Congress which, despite a few last minute cancellations following the USA raids on Afghanistan and the Sudan, was attended by over 600 delegates. With the excessive temperatures and incessant noise from car horns and sirens outside, the air-conditioned lecture theatres and coffee bars provided a welcoming environment for lectures, workshops, poster presentations and informal discussions. Each day commenced with a plenary lecture followed by several sessions running concurrently. Time-tabling clashes led to a few dilemmas over which session or talks to attend, although this was alleviated to a certain extent by some well-disciplined timekeeping. The poster sessions included over 300 presentations and were all held over lunchtime, which created a few problems due to overcrowding in the poster hall and limited opportunities to view posters at other times. The extensive evening social programme included visits to a sound and light show in the Citadel of the Old City, a viewing of the Dead Sea Scrolls at the Israel Museum, and a `folklore' evening, thus ensuring that we received both a scientific and a cultural education!
The opening keynote lecture, given by Stephen Oliver (UMIST), was a review of how the completion of the Saccharomyces cerevisiae genome sequence was likely to lead to major advances in mycological research, particularly using some of the elaborate molecular biology techniques to which yeast is amenable (techniques those of us who work on obligate biotrophic plant pathogens can only dream about!).
Among the highlights on the first day was a session on population genetics. Christian Damgaard (Denmark) presented a theoretical discussion of co-evolution of plant/pathogen gene-for-gene systems in which metapopulations can be considered as the sum of many sub-populations, each going through their own boom and bust cycles. What was less clear was how such models might be tested.
Austin Burt (Imperial College) then discussed the roles of sexual and asexual reproduction in population genetics, culminating in a discussion as to whether any truly asexual fungi exist, or whether in those cases where sexual cycles have not been observed it is simply occurring at very low levels. Linda Kohn (University of Toronto) expanded this debate into a discussion of speciation.
The afternoon sessions contained several impressive examples of the
use of Green Fluorescent Protein (GFP) for imaging components of living
cells. Xin Xiang (New Jersey) examined the role of the motor protein dynein
in moving nuclei along microtubules in Aspergillus nidulans. Using
GFP-tagged dynein and tubulin, she found evidence that nuclear migration
requires a concentration of dynein at the hyphal tip. GFP is also being
used as a marker in novel mutant screens. Nicole Sievers (Marburg) described
use of an A. nidulans strain with GFP-stained nuclei for rapid identification
of mutants with defective nuclear migration or morphology. Selected
mutants were then tranferred to culture plates by micromanipulation. Similarly, Cees van den Hondel (Leiden) reported the use of GFP fused to glucoamylase (a wall-targeted protein) to identify secretion-deficient mutants in A. niger.
The Tuesday plenary session was given by David Hawksworth (MycoNova) and reviewed just how little we know about fungal biodiversity _ of the estimated 1.5 million species of fungi on earth, less than 100,000 have been named, and the resource potential in the remainder is enormous.
A session on economic and applied aspects followed. Derek Hollomon (Long Ashton) explained how the problem of fungicide resistance has so far been minimised by monitoring fungicide sensitivity, deploying new chemicals with novel modes of action, and restricting the use of certain `at risk' products. He highlighted the potential of `molecular beacons' (fluorescent PCR primers) for detecting low frequency mutations in particular target sites within pathogen populations to give early warning of emerging resistance problems.
Disease control using Bion was reviewed by Oostendorp (Novartis). The compound seems to mimic the action of salicylic acid because in Arabidopsis mutants where SAR is not inducible by pathogens or salicylic acid, it cannot be induced by Bion either. Activation persists much longer in monocots than dicots and the compound is not effective in those plants where SAR does not normally operate. Bion can help to reduce the number of applications of conventional fungicides when used as part of an integrated control strategy.
After lunch, the theme was the infection process. Pappachan Kolattukudy (Ohio State) gave a comprehensive review of pre-penetration events, starting with removal of spore self-inhibitors, priming of the fungus to germinate through calcium/calmodulin signalling and a set of hard surface-induced genes, followed by induction of genes for appres-sorium formation by chemical signals.
Kurt Mendgen (Universitat Konstanz) reviewed his work on the bean rust fungus, and the isolation of plant-induced genes (PIGs) from a haustorial-specific library. Amongst the interesting findings was the fact that the rust ATP-ase gene was more similar to that from Vicia faba than to those from other fungi. Also, from the PIG genes isolated, it was suggested that rusts may have no biosyn-thetic pathways for lysine and arginine and therefore need to transport these from the plant. This led to speculation that the haustoria might be an elaborate means for fungi to go beyond obtaining nutrients from the apoplast by providing access to the cytosol, where amino acids are more abundant.
The endophytic cereal pathogen, Claviceps purpurea, provides an interesting model to study biotrophy as it is culturable and transformable. Paul Tudzynski's group at University of Munster has cloned several genes encoding xylanases, catalases, superoxide dismutase and a novel cell wall protein containing three hydrophobin domains, and they are now assessing their role in pathogenicity by gene knock-outs. EST analysis based on a cDNA library of infected rye tissue showed that fewer than half of the 100 genes so far sequenced show any homology to known genes.
On Wednesday, the plant pathology switched to virulence determinants in fungi. Wolfgang Knogge (Max-Planck) discussed the isolation of the Nip1 gene from Rhynchosporium secalis, and the hydrophobin-like structure of the gene product. Evidence was presented that when the gene was knocked-out, the fungus was less pathogenic on susceptible plants, adding weight to the argument that there is a cost to virulence in fungi.
Interestingly, in most of the naturally occurring virulent fungal races, the gene is lost through a total deletion, rather than point mutations accounting for loss of function. This is becoming a recurring theme in avirulence determinants. Although there are examples of genes (such as Avr4 in Clado-sporium fulvum) where function is lost by point mutation, there is also increasing evidence for gene deletions, chromosomal rearrange-ments and transposable elements in fungal genomes.
Also in this session was a talk from Dov Prusky's group (Israel) on latent infections of Avocado by Colletotrichum gloeospori-oides. They had shown that secretion of pectic lyase by the fungus was important for infection, and that this did not occur at pH less than 5.8. In unripe avocado, the pH in the pericarp is low at first, rising above 5.8 only when the fruit ripens. In one of their resistant cultivars, the pH in the pericarp never rose above 5.8, which might account for the resistance.
Wednesday afternoon was devoted to a series of Workshops. Probably the best-attended of these concerned image analysis of fungi, although a more accurate title may have been the `Spitzen-korper workshop'. Salomon Bartnicki-Garcia (University of California) started by reviewing the major contribution that video microscopy has made to understanding the role of the Spitzenkorper in orchestrating tip growth and fungal morphogenesis. Rosamaria Lopez-Franco (ITESM, Mexico) and Charles Bracker (Purdue) presented spectacular video sequences of growing hyphal tips, viewed with digitally-enhanced phase contrast micro-scopy. Laser microbeams were used as `optical tweezers' to push the Spitzenkorper around the cell to study effects on morphology and the direction of apical growth. Nick Read (Edinburgh) described an interesting new vital dye for imaging the Spitzenkorper in growing hyphal tips. The fluorescent dye transiently labels the plasma membrane but is rapidly internalised into endosomes before accumulating in the Spitzenkorper. Nick also reviewed ratio imaging techniques for the measurement of intracellular pH and ion concentrations within hyphae, highlighting some of the potential problems and pitfalls.
On Thursday, Pierre de Wit (Wageningen) discussed the C. / tomato interaction, and in particular the Avr4 and Avr9 genes and the corresponding resistance genes in tomato. Olin Yoder (Cornell) then presented his work on Cochliobolus heterostrophus, presenting evidence of a massive rearrangement in the genome of the fungus to account for race T of the pathogen, the cause of the Southern Corn Leaf Blight epidemics of the 1970s. Race T not only has a reciprocal translocation from the original Race 0, but in the process it has picked up between 1-2 megabases of alien DNA, of completely unknown origin. Results were also presented of REMI mutagenesis experiments on C. victoriae, which showed that disruption of a peptide biosynthesis gene Cps1 resulted in loss of pathogenicity but the fungus was still able to produce Victorin toxin, indicating that the toxin alone does not cause disease symptoms.
A final session of interest was on mycorrhizal fungi. Although difficult organisms to work with, there is much interest in these fungi because of their plant growth promotion effects and also their potential role as biological control agents against some soil-borne pathogens. The groups of Guillaume Becard (Toulouse), N. Requena (Max-Planck) and Luisa Lanfranco (Turin) have been able to develop a range of differential display and PCR based techniques to isolate and clone genes involved in the early stages of the mycor-rhizal/ plant interaction. I. Ginzberg, (Volcani Center, Israel) presented her work on the effect of mycor-rhizal fungi on plant defence-gene expression. Interestingly, the fungi caused a delay in PR protein expression and also suppressed the induction of these genes by chemical agents such as BTH. Suppression also occurred in leaves, possibly as a result of increased cytokinin levels. The argument was presented that this accounts for the increased susceptibility of mycorrhizal plants to foliar pathogens. On the other hand, physical exclusion of root pathogens may explain the observed biological control of these diseases.
The Congress was well-organised, informative and thoroughly enjoyable, and we are extremely grateful to BSPP for the travel awards that enabled us to attend. And what about our own presentations at the conference? Well we can only assume that they went down well and that news travels fast in Israel. What other explanation could there be for the intense interest shown by the security staff at Tel Aviv airport in checking through the abstracts and our slides as we were leaving the country!
Matt Dickinson, University of Nottingham
9th Conference of the ISHS Vegetable Virus Working Group
Turin, Italy : 22-27 August 1998
The International Society of Horticultural Science (ISHS) formed the Vegetable Virus Working Group in 1971. One of the main aims of this group is to bring together vegetable virus research workers from all over the world to discuss current work interests. This is achieved by organisation of an international conference every three years. The 9th Conference of the VVWG was attended by about 70 participants from 19 countries. The conference programme consisted of paper and poster sessions, evening visits to local sites of interest and a technical excursion to the Italian Riviera.
On the evening of our arrival in Turin, a welcome buffet was held in the grand setting of the Palazzo Cisterna, a palace built in the seventeenth century which now houses Turin's local government. After a brief guided tour around the palace's magnificent rooms, delegates tucked into an equally impressive array of food and drink kindly provided by our hosts.
The first full day paper session began the next morning and was concerned
with identification, characterisation and new viral diseases of vegetables.
The session began with a review by H. Huttinga on diagnosis, identification,
characterisation and detection of virus diseases. This was a great introduction
to the day's 13 paper presentations in which viruses from 9 different genera
were discussed. Amongst these was the first report of a phytoreovirus in
Africa associated with leaf-curl in tobacco, presented by C. Rey; a report
on the incidence of two potyviruses,
zucchini yellow mosaic virus (ZYMV) and watermelon mosaic virus (WMV) in the Netherlands, by J. Verhoeven and a report on the use of 5'-end nucleotide sequence to clearly distinguish between luteoviruses, turnip yellow virus (TuYV) and beet mild yellowing virus (BMYV), which are almost indistinguishable on the basis of host range, symptom expression and serology, presented by J. Schubert. Two papers in the afternoon discussed the occurrence of phytoplasmas in tomato.
The day was concluded with a visit to the botanical gardens of Turin University. These gardens were founded in 1792 and now cover a total area of 30 thousand square metres. In some areas of the garden the traditional Piedmontese vegetation has been recreated. The gardens also contain greenhouse facilities and scientific laboratories.
The next day continued with a half day paper session entitled `Ecology
and epidemiology' followed in the afternoon by the poster session. The
morning's key lecture was by J. Duffus who gave an entertaining talk on
the impact of virus ecology and epidemiology studies in California agriculture.
H. Lecoq presented the second key lecture of the day on the ecology and
epidemiology of potyviruses, the largest group of plant viruses whose members
are distributed worldwide and therefore, unsurpri-singly, featured strongly
in this day's paper presentations. The poster session after lunch covered
a range of topics. Afterwards there was a visit to the Istituto di Fitovirologia
Applicata where we
were shown around the laboratories and glasshouses, built in the early 1990s. An interesting feature was an underground tunnel which linked the main building to the glasshouses. This was built in order to avoid the risk of vectors entering the glasshouses at certain times of the year and no doubt to keep the research workers warm and dry at other times of the year!
After two full days of paper and poster sessions a technical excursion was arranged for the third day. This allowed us to make the most of the unusually warm weather, but also meant an early start for the 3 hour drive southwards to the Italian Riviera. The time passed quickly, though, as we drove through splendid scenery to the first stop of the day. We arrived at a growers, where we basked in the sun while being shown greenhouses and fields of basil which is used in the production of Ligurian pesto and in the heat was giving off the most fantastic aroma. The next stop was the Centro Regionale di Sperimentazione ed Assistenza Agricola (CeRSAA). This is the Albenga regional centre for agricultural aid, which was established to promote the use of new technology and provide technical support to the region's growers. Among the many services it provides is a disease diagnostic service and test facilities for resistant plant cultivars and new cultivation techniques.
After lunch we had a guided tour of the thirteenth century walled town of Albenga and visited an olive oil mill situated in the wall of the town. The final visit of the day was to a grower who had lost a whole crop of peppers to tomato spotted wilt (TSWV) and cucumber mosaic virus (CMV), with the exception of a small number of a new resistant variety which were on trial and were unaffected. This illustrated just how devastating virus infection can be to crops and the value of developing new resistant varieties.
The final full day paper session was entitled `Control, including engineered
resistance'. The morning started with a key-note lecture by B. Raccah on
the control of vector-borne viruses by managing host susceptibility and
vector activity. This was a very interesting talk and described the practices
used to protect crops from the devastating consequences of virus infection,
which we had witnessed with the pepper crop only the day before. An interesting
point made was how even the simplest of techniques, such as placing a tightly
woven netting over the crop or covering the ground with UV reflective plastic,
can very effectively prevent insect vectors reaching the plants and transmitting
eases. Amongst the other papers that morning was my contribution to the meeting, where I reported the findings from my PhD research into the identification of novel genes for resistance to bean common mosaic virus (BCMV) in Phaseolus vulgaris.
After lunch, the session restarted with a key lecture by B. Gronenborn entitled `From replication to resistance: Geminiviruses and beyond' in which he described the development of transgenic plants expressing altered replication initiator proteins (Rep) of geminiviruses which are resistant to geminivirus infection. This theme was continued in the rest of the afternoon papers, where engineered resistance of plants by the expression of a virus gene was discussed for a number of plant viruses. A paper by O. Le Gall described the use of infectious cDNAs to study the pathogenicity of lettuce mosaic potyvirus (LMV). Papers on transgenic plants promoted a lively debate, where the benefits and risks of using such plants were discussed and many, varied opinions put forward.
As it was the last night of the conference a social dinner had been organised. This was held in the courtyard of a nearby medieval castle situated along the banks of the River Po. The castle is contained within a medieval village complex, all of which is a replica of a 15th century Piedmontese village built for the 1884 International exhibition of Turin. As with the rest of the week there was plenty of delicious food and wine.
The last day of the conference consisted of a half-day paper session entitled `Host-pathogen interactions', including a very informative key lecture from P. Palukaitis in which he discussed the strategies, routes and barriers to virus movement within plants. I would especially like to thank Maurizio Conti, Piero Caciagli and everyone else responsible for the organisation of such a successful conference. I would also like to acknowledge the generous award from the BSPP travel fund which made my attendance possible.
Georgina Donovan, University of Birmingham
2nd International Rice Blast Conference
Montpellier, France : 4-8 August 1998
Rice is a major staple food for approximately two-thirds of the world's population. More than 90% of the world's rice is both grown and consumed in developing countries. The ever increasing population in these countries places heavy demands on enhancing rice production. Blast, caused by Pyricularia grisea (teleomorph Magnaporthe grisea) is the most widespread and damaging disease of rice in most regions. The disease is so complex and diverse that it requires concerted efforts from scientists to work together to reduce its impact.
About 120 scientists from more than 24 countries gathered in Montpellier from 4-8 August 1998 before the International Congress of Plant Pathology of Edinburgh to share their experiences and latest findings regarding this important disease of rice. The congress was held at the AGRO, the National Agricultural School, in Montpellier, a city about 500km from Paris with a varied cultural life and a superb Mediterannean climate.
The themes for the conference sessions included: host resistance; breeding and selection strategies; pathogen population studies; pathogen genetics and molecular biology; epidemiology and integrated pest management. There has been a tremendous accumulation of knowledge in the past decade especially with the development of molecular techniques and the mapping and cloning of genes involved in pathogenicity - all with the aim of better understanding the pathogen and providing ways to control the disease.
Barbara Valent gave a general introduction on developments in rice blast research over the past five years . As the main goal is to provide rice farmers with varieties possessing more durable resistance to blast, she stressed the importance of understanding the molecular mechanisms behind host-pathogen interactions, understanding the population biology and potential for evolution of the rice blast pathogen and understanding the evolution and behaviour of rice resistance genes. Next, several speakers described work on the molecular and genetic analysis of disease resistance, including map-based studies of resistance genetics.
The first day concluded by with a look at various breeding strategies employed in different rice growing areas of the world and this theme continued next morning. Speakers looked at some of the old and new methods used to control rice blast, including the use of Sasanishiki multilines (near-isogenic lines with different complete resistance genes to blast) in Japan and the use of lineage-exclusion resistance breeding. This strategy involves combining resistances to exclude all lineages in the pathogen population. This contrasts with the conventional strategy which combines resistances to exclude observed virulence types. The former strategy has so far been useful with the Colombian cultivar Oryzica Llanos 5 introduced in 1989 which, so far, has not broken down to blast. The important message here was that combinations of genes that in total confer resistance to every lineage will confer resistance to the entire blast population.
A poster session then followed where I had the opportunity to present my work on the genetic and pathotype diversity of the rice blast fungus in West Africa. Such studies have not previously been conducted in this important rice growing region. Field isolates of M. grisea are genetically homogenous and stable, while each of the West African countries covered has at least 3-5 distinct lineages and 3-5 pathotypes. M. grisea isolates from other hosts appear to be present on rice at low frequencies, but their epidemiological significance is unknown as they are not pathogenic on the susceptible rice cultivar, CO39. It is anticipated that my study will lead to a better understanding of the diversity and distribution of blast genotypes and pathotypes in this region.
On Thursday, the session opened with pathogen population studies as the theme, with papers on the population biology and genetic organisation of the rice blast fungus in various regions. One notable paper gave evidence for recombination in M. grisea in the Himalayas and inferred that recombination affects the population structure and dynamics of M. grisea. A heated debate ensued with some for and others against this notion.
The conference continued with pathogen genetics and molecular biology, focussing on appressorium formation and the penetration process of the fungus. Signalling pathways involved in these processes and pathogenicity factors were discussed by John Hamer, Nick Talbot, Barbara Valent and others, who described the molecular basis of pathogenicity and identification of pathogenicity genes using such techniques as insertional mutagenesis or the use of pathogenicity mutants. This theme continued in the final morning, focussing on the identification and isolation of avirulence genes in M. grisea, followed by genomic organisation and variability. The theme for the last session was epidemiology and integrated pest management where different strategies were discussed for rice blast control, including the use of silicon in irrigated and upland rice ecosystems and varietal field resistance. The use of fungicides such as azoxystrobin and metominostrobin were also discussed.
The congress was well organised, discussions were stimulating and provided a great opportunity to meet others working on this crop and fungus. A data base for M. grisea is now available on the internet, integrating information on the disease. This currently includes an extensive bibliography, a genetic map, a physical map and data on the rice blast populations in Europe and the Philippines, including DNA fingerprint variation, lineage structure and pathotype information. Work is underway to incorporate information on additional blast populations worldwide. It can be accessed at http://probe.nalusda.gov:8000/plant/aboutRice BlastDB.html. When fully developed, it is hoped this database will facilitate greater understanding of the genetics of pathogenesis and host-plant resistance, and serve as a guide to breeders for resistance gene deployment.
Another key point was the need to have the whole of the rice blast fungal genome sequenced. Rice genome sciences are well advanced due to major genome initiatives in Japan, China and Korea, and a new international project to sequence the entire rice genome has set goals for completion of 40% of the rice genome sequence by the year 2003. It is estimated that there are about 9,000 genes of the rice blast fungus that will require sequencing.
I am very grateful to the BSSP and the SGM for their generous contributions that made it possible for me to attend the conference which I found rewarding and which gave me an enjoyable experience. I am also grateful to Natural Resources International/DFID for funding the project and to all involved in this work which is a joint project between HRI, International Mycological Institute, NRI and the University of Exeter.
Jack Chipili, Horticulture Research International, Wellesbourne
Broomrape in Bulgaria : September 1998
In the summer of 1998, I was pleased to be able to keep a promise made
to Dr V Entcheva to visit the Institute for Wheat and Sunflower (IWS) to
complete studies on the parasitic weed Orobanche. Dr Entcheva had
worked with me as a Royal Society Fellow at Long Ashton Research Station
in 1996. My visit was planned to coincide with the Fourth International
I travelled from Clevedon via Gatwick to Albena via Varna and Sofia. Accommodation was provided by IWS at their "Rest House", a small hotel situated in a forest a few minutes above the Black Sea. Despite strong assurances that the weather in September would be perfect, I was greeted by good old fashioned West of England fare: cool and very wet. Planned visits to collect samples of Orobanche from Artemesia growing on the coast near the Romanian border had to cancelled, but this did provide a greater opportunity to plan future publications.
The Workshop attracted more than 100 scientists, especially from countries adjoining the Mediterranean, where broomrapes are important. The presentations covered a wide subject area, dealing with aspects of research that ranged from trying to understand the basis of infection and parasitism, to very practical problems associated with the identification of the parasites and the effectiveness of control measures.
My host, Dr Entcheva, was one of the Organisers, along with Professors K Wegmann, D Joel, L Musselman and C Parker. The major Sessions were:
Germination, Physiology and Biochemistry
B. Zwanenburg (The Netherlands): reviewed the identification of natural germination stimulants, i.e. strigol and surgolactone, and reported progress on the synthesis of stimulant analogues. A Shomer Ilan (Israel): described the wide array of wall-degrading enzymes isolated from germinating Orobanche seedlings thought to be involved in the wall-separation of host cortical cells by the parasite.
Penetration of the Germ Tube and Establishment of Haustoria
D. Joel (Israel) reviewed the beautiful differential changes that occur when Orobanche seedlings infect host roots. His photographs illustrated the formation of a swollen "appressorium" at the tip of the parasite's root where papillae formed and the intrusive cells that pass through the host cortex. J. Westwood (USA): revealed for the first time that Arabidopsis is highly susceptible to Orobanche aegyptiaca. He discussed the potential for Arabidopsis as means for studying the mechanisms of infection and resistance.
D. Joel (Israel) reported specific DNA markers that could be used to identify different species of Orobanche. Through collaborative work with P. Thalouarn (France) several new species have been established. A. Ljubenova (Bulgaria) discussed the molecular evolution of parasitism, where it appears that plant parasitism has evolved eight times.
Resistance to Orobanche and Resistance Breeding
C. Alonso (Spain) presented a masterly review of the resistance of various crops to Orobanche. Resistance has been extremely effective in sunflower, where the genetic basis of several resistant varieties is well established. However, he reported that many commercial varieties of sunflower were now being attacked by the parasite because new highly aggressive races were widespread in Spain and Turkey. He outlined the mechanisms of resistance. Such studies are at best preliminary and conclusions that induced lignification and formation of phytoalexins are important need to be further evaluated. Y. Goldwasser reported that induced synthesis of phenolics and lignin was associated with a hypersensitive-like response involving the death of many host root cells around the invading Orobanche parasite.
Progress in Orobanche Control
Much emphasis was placed on the use of herbicides to control these parasitic "weeds". Although a traditionally strong research area, problems continue to arise through both the host and parasitic partners being sensitive, at least to some extent, to the herbicides used. Successful control requires that application rates are carefully regulated. This is being achieved in irrigated fields in Israel, but such procedures do not seem readily applicable to less developed agriculture systems.
Scientist at the Institute for Wheat and Sunflower described their research in a series of posters. Shindrova et al. showed that yield losses in sunflower were accompanied by reduced oil and protein yields. Nicklova et al. reported new forms of sunflower with resistance to O. cumana derived from perennial sunflower species. Petakov et al. and Christov et al. reported new sunflower lines resistant to Orobanche, mildew and Phomopsis, a fungal disease which has increased greatly in importance during the last few years. Finally Iliev et al. described an alternative approach based on biocontrol.
The proceedings of the Workshop will be published. Details are available from Dr V Entcheva, Institute for Wheat and Sunflower Research "Dobroudja", near General Toshevo, Bulgaria. E Mail: IWS@dobrich.net. Any one wishing to be more informed about parasitic plants, e.g. news of meetings, recent research progress and the latest publications should read "Haustorium - the Parasitic Plants Newsletter". This is available by E Mail from ChrisParker5@ compuserve.com
The remainder of my time in Bulgaria as spent visiting the Institute for Wheat and Sunflower (IWS). The Institute has two sites, both in the NE of Bulgaria, in the Dobrudja region. The largest site is near General Tosheva, where all the field trials and experiments are done. Also at this site is the farm that produces elite wheat and sunflower seed. The latter has been a major success for the Institute. One of their sunflower varieties, Albena, has been planted widely (20-40% of total acreage) in France. I visited the Dobrich site where the main laboratories are sited about 20 kilometres south, where I was able to see their facilities, continue various discussions and even present a seminar on mechanisms of infection, phytoalexins and disease resistance.
I also had the unforgettable experience of travelling to Sofia with Dr Peter Ivanov, Director of IWS, and Dr Entcheva: 500 kilometres each way in a Lada fitted with a radar speed detector!. One highlight was visiting a Bulgarian farmer on the outskirts of Sofia. When we arrived at his farm, you can imagine my surprise when the boot of the Lada was opened to reveal two 40 Kg bags of wheat seed. The IWS Director had agreed to deliver it on his next visit to Sofia. I have to say that the Lada did not appear to have noticed the extra weight, though after we left the farm the strange noise on the back axle had disappeared!! The return trip had equal highlights: being startled on a motorway by the car swerving to miss a cow, then within the next minute or two overtaking several horses and carts and finally to pass a decorous young lady plying her trade. It really was quite different from driving on the M5!
I am very grateful to the British Society for Plant Pathology for covering all the costs involved in travelling to and from Bulgaria. While in Bulgaria I was the guest of the Institute for Wheat and Sunflower. I enjoyed greatly the friendly welcome from all IWS staff and much appreciated the accommodation provided in their guest houses in Albena, Dobrich and Sofia. I am particularly indebted to Dr Entcheva, who was my guide at all times, and to Dr Peter Ivanov, Director of the IWS for his generous hospitality, provision of transportation and his introduction to Bulgarian history.
John Bailey (email@example.com)
10th International Sclerotinia Workshop
Fargo, North Dakota, USA : 9 -12 September 1998
The workshop was organised and hosted by Drs. Berlin Nelson and Tom Gulya of the Department of Plant Pathology, North Dakota State University and the USDA-ARS respectively. There were 82 registered delegates, all from the US apart from five from Canada, one from Sweden and myself. The workshop covered occurrence, distribution, basic biology, pathology, ecology, epidemiology, chemical and cultural control, IPM and biological control.
I presented a brief review of Sclerotinia in the UK and also two posters on winter oilseed rape in conjunction with Caroline Young (ADAS) and on field lettuce in conjunction with Caroline, and John Whipps and Simon Budge (HR1-Wellesbourne). It was apparent that there were numerous methods (published and unpublished) to induce carpogenic germination of sclerotia and the organisers requested that researchers should send in details of their own method for inclusion in the final version of the workshop report.
Jim Steadman and his team (at the University of Nebraska in conjunction with the University of Wisconsin) used RAPD to differentiate mycelium of Sclerotinia sclerotiorum, S. trifoliorum and S. minor but cannot detect intraspecfic virulence variation. In addition, there are three restriction enzyme generated PCR-RFLP patterns that show species differentiation, growth rate, sclerotial size and development and also mycelial interaction. PCR-RFLP based species identification can be done in 24h. Work on species identification by RFLP analysis of isolates of Sclerotinia spp. from canola (spring-sown oilseed rape ) was reported by Dan Phillips (University of Georgia) with Linda Kohn (University of Toronto) and all were S. sclerotiorum.
A manual of the "The Blue Plate Test" was presented which was developed by Jim Steadman and colleagues for field use to forecast white mould in soya beans. The test agar consists of agar plates containing a semi-selective medium containing the pH indicator bromophenol blue - the agar changes colour from blue to yellow in response to oxalic acid produced by S. sclerotiorum. This test was evaluated by ADAS in the UK in winter oilseed rape to detect S. sclerotiorum on petals but unfortunately cross reacted with Botrytis cinerea. It was also apparent that very little work had been carried out on the understanding of the molecular genetics of S. sclerotiorum.
Oxalic acid plays a role in pathogenicity and one test using oxalate to indirectly test for physiological resistance to white mould in dry beans was presented by Judith Kolkman (University of Michigan) whereby 20d seedlings were cut at the stem base and immersed in 20 mM of oxalate (Sigma) at pH 4.0. Plants were rated for wilting symptoms after 12-15h. Results showed that wilting symptoms in tests had a strong, consistent correlation to disease in the field. In a similar test Stephen Wegulo (Iowa State University) found a red coloration produced in solution (as described above) was related to resistance. Lu and co-workers (Pioneer Hi-Bred International) found a detoxifying gene in wheat for oxalate oxidase which was used to transform a sunflower inbred line with significantly enhanced resistance in glasshouse trials.
Marc Cubeta (one of our Journal editors) and colleagues at N Carolina State University, working on S. sclerotiorum of cabbage demonstrated that freezing and wounding may be important factors pre-disposing infection. This is the first time that freezing injury has been experimentally demonstrated to be of importance. Marc also reported fungicide evaluation with good protection given by fluazinam, azoxystrobin (Zeneca), Rovral, Ronilan, Topsin M (tbz), fludioxonil (Novartis) and BWC01402F and BWC01201F (the latter both from BASF). Conio-thyrium minitans applied as a foliar spray of > 500 spores mm-2 reduced infection in dry beans apart from conditions of very high disease pressure as reported by Bremer (Agrim) and Huang (Agri-Food) and co-workers (Lethbridge, Canada). Apetalous canola has been developed by Jurke (Zenica Seeds) and colleagues, with the first line ZNA 005 submitted for Canadian registration in 1997. From a limited number of trials, significantly lower disease was recorded in the apetalous line compared with normal lines with also increased yield, protein and oil content.
An invitation was extended by Nigel Hardwick to host the next workshop in July 2001 at York. There was a favourable response and this would be the first time since the start of the workshops in 1974 that the venue has been outside the US apart from the sixth and eigth held at Saskatoon and Toronto, Canada in 1986 and 1993, respectively.
The journey to Fargo did not go to plan. Air tickets to Fargo and back had been organized in June but on the Friday before my departure the following Monday I was informed that NorthWest Airlines were on strike. Luckily I was able to get a flight to Chicago with a 3.35 am start from central London (a night bus, N 97, which must be the best value connection to Heathrow at £1.50). After arrival in Chicago, I had a "tube" ride to Union Station in the city centre, a 5h wait and then a 15 h train ride to Fargo arriving 6.00 am - a journey not to be taken lightly after a 9 hr flight! After a rest, I was able to tour the CASE tractor plant.
The conference started on Wednesday evening but Thursday was the hottest day of the year in Fargo 35.6oC and fortunately the hotel was air conditioned. I was unable to get a space on the train to return to Chicago (in the US all seats have to be prebooked and only one train a day - I will never again criticise British Rail) and would have had to leave at 2.15 am. I was extremely fortunate in obtaining a lift from Wayne Pedersen, Glen Hartman and Juju Manandhar all working on white mould of Soya beans, an 11h journey with an overnight stop. I stayed with Wayne and his wife and 2 children and was made most welcome. I was invited to a lakeside picnic dinner to celebrate the retirement of Dr. Robert Ford, Head of Plant Pathology at the University of Illinois-Urbana Champaign.
On Sunday after church we all went to Arcola some 35 miles South West of Urbana to a broom corn festival. Broom corns are sweeping brooms made from grass sorghum as opposed to seed sorghum and I have had one in my garage for years but did not know its origin! Later that day I visited some of Wayne's experiments on soya which had a low incidence of disease. Driving through the area which was exclusively corn and soya, the GM crops of each, which were in the majority, were easily identified because of the absence of weeds.
I acknowledge ADAS for financing the trip and allowing me to attend the workshop.
John Davies, ADAS Terrington
Application of Biotechnology in the Improvement of Jute, Kenaf and Allied
Beijing, China : 22 - 25 November 1998
Wagon covers in the Wild West, sand bags in the First World War, wallpaper, clothing, hats, rope: these are just some of the diverse products made from jute (Corchorus) or its associated fibres kenaf or mesta (Hibiscus), collectively known as JAF (jute and allied fibre) crops. In the UK, Dundee was the city of "jute, jam and journalism". As a sea port and a centre of manufacturing, Dundee's history is closely linked with jute, in an industry which employed 50,000 people at its peak and supplied all the world's demand for jute products.
One of the reasons for the decline of the industry was competition from the new synthetic fibres. Nonetheless JAF crops are alive and well and enjoying a resurgence because of their "naturalness". They are produced by small scale farmers in Asia, with Bangladesh being the largest producer, the other main countries being China, Thailand, India, Nepal and Indonesia. Dhaka in Bangladesh is the home of the International Jute Organisation (IJO), the administrative, co-ordinating, promotional and research commissioning body for the industry. Dr Aimin Liu from the IJO organised this workshop which was hosted by the Chinese Academy of Agricultural Science in Beijing; the local organiser was Dr Gong Xifeng. The workshop had representatives from Bangladesh, China, Thailand, Indonesia and the UK (myself); a delegation from India was unfortunately unable to attend. The objective of the workshop was to review the current state of technology in the improvement of JAF crops, to assign the next research priorities in the application of biotechnology towards improvement, and who will carry these forward. JAF crops are seen as "poor farmers" crops and have not had anything like the technological input which the major food crops have had. Biotechnology will impact on: (i) overcoming incompatibility barriers to hybridisation between species within Corchorus and Hibiscus; (ii) haploid breeding using anther and pollen culture (iii) new genotypes from somaclonal variation (iv) generation of transgenic jute and kenaf with improved insect and disease resistance, lignin reduction and fibre yield.
A programme of genetic improvement using biotechnology was initiated in 1996: this was Phase 1 of the programme, for which the major research priorities were the development of a transformation system, development of efficient tissue culture techniques, identification of appropriate genes for transformation, construction of a molecular map, and development of fingerprinting techniques for JAF accessions. Workshop participants presented progress reports in these priority areas. An efficient system of plant regeneration from excised cotyledons of jute (Corchorus capsularis) has been established; a similar system is under way with kenaf (Hibiscus cannabinus). Crosses have been made between 20 parents of different species of Hibiscus, and embryo rescue has yielded several plantlets from inoculated ovules. An efficient protocol for Agrobacterium-mediated gene transformation in jute has been established. RAPD markers were used to identify varieties within jute and kenaf, and to examine phylogeny amongst kenaf species.
Research priorities for Phase 2 of the Programme, due to start in 1999, were then discussed at the workshop. These were genetic transformation of jute for resistance against insects - jute hairy caterpillar (Spilosoma obliqua) and stem borer (Apion corchori) - and stem rot disease caused by Macrophomina phaseolina, a major problem in jute. Another priority is the characterisation of JAF germplasm using molecular markers for agronomic, pest and disease resistant traits, which was the topic on which I presented my contribution. The next two years should see some major progress.
In addition to the Workshop, participants had the opportunity to visit the Biotechnology Research Centre (BRC), part of the Chinese Academy of Agricultural Sciences. The breadth and successes of plant biotechnology research in this Institute is truly mind boggling. Much of the effort is directed towards cotton, the most important cash crop in China - some examples of work conducted on cotton at the BRC are the production of transgenic varieties containing Bt (against the cotton bollworm); dual Bt/coat protein genes (the latter against virus); genes for: aphid resistance; resistance against Fusarium and Verticillium wilt diseases. Other crops in the research programme with resistance transgenes are potato (bacterial wilt caused by Pseudomonas sola-nacearum; PVY), rice (bacterial blight), wheat (coat protein gene against BYDV).
Between sessions there were of course lunchtimes and dinner times - and the opportunity to sample Chinese food. Whilst Chinese breakfasts are disappointing, the rest of the day was a treat and we were generously supplied with a huge range of delicious food including the famous Beijing duck. Alongside more usual (bearing in mind my reference point is my local take-away) meat and vegetable dishes I sampled jellyfish and sea cucumber. Other items on the menu, I noticed, but not served were fried bullfrog, anteater, snake and 1000 year eggs traditionally matured in horse's urine, giving credence to the Cantonese claim that "if it's got four legs and it's not a table, we'll eat it". And why not.
We were entertained one evening with Chinese acrobatics at the Chaoyang Theatre - rubber-bodied people doing cunning stunts with unicycles, hoops, masses of spinning plates, or just piling bodies into impossibly high structures. We left feeling that these people were more than human beings. The meeting was rounded off by a visit to the Great Wall at Badaling. It was a bitterly cold day, snow had just fallen. The Wall rises and falls into the distance over precipitous peaks, many of which were engulfed in cloud - truly awesome. The Wall is apparently the only man-made structure visible on earth from the moon, but an American tourist we met reckoned so was the Staten Island garbage dump.
For the chance to participate in this productive and enjoyable workshop, my thanks go to Porntip Wongkaew of Khon Kaen University, Thailand, and Aimin Liu of the International Jute Organisation, Dhaka, Bangladesh, for the invitations and to the BSPP for a Travel Grant.
Rob Harling, Scottish Agricultural College
Clubroot in Japan
International Clubroot Working Group
Fukushima: Nov 1998
Vegetable brassicas form a major component of the diet in Japan and are very intensively cultivated. Clubroot, caused by Plasmodiophora brassicae, is an increasingly serious cause of loss in these crops. The publicly-funded sector and private industry are combining in an attempt to control this problem.
As part of this programme I received a `Research Award for a Foreign Specialist', from the Japanese Ministry of Agriculture, Forestry & Fisheries in November. This enabled me to visit for a couple of weeks centred at the Tohoku National Agricultural Experiment Station, Fukushima. An International Clubroot Working Group Meeting held in Fukushima formed the focal point of this visit. The crucial importance of this pathogen was immediately obvious from the attendance of over 80 active specialists, mainly Japanese, at the Meeting.
Japanese industry has developed the fungicide `Nebijin' (= Beautiful Roots), common name flusulfamide, which is now widely and successfully used. It is recognised, however that this molecule can form only part of a control strategy. Dr Shuhei Tanaka of Yamaguchi University is studying both the mode of action of Nebijin (which relates to cleavage to the walls of resting spores) and the distribution of variation in populations of P. brassicae using isozyme and RAPD pattern analyses.
Developing resistant lines of Chinese cabbage has been successfully achieved at the National Institute for Vegetables, Ornamentals and Tea (NIVOT) by Dr Kuginuki and colleagues. He described the breeding programme, associated tests with populations of P.brassicae and the development of host linkage maps with estimated quantitative trait loci (QTLs).
Private sector breeding has led to the development of radish hybrids (Daikon) with high resistance to P. brassicae and great popularity with the consumer (Takii Company). Dr Tsushima of the Department of Integrated Agricultural Research at Fukushima has elegantly demonstrated the manner by which Daikon may be used as a decoy plant encouraging the germination of soil-borne resting spores. The inoculum potential of P. brassicae is thereby diminished.
The Fukushima Research Station is endowed with fields that are conducive and suppressive to P. brassicae. Hence possible cultural and biological control strategies are receiving close attention. Success in this direction has been achieved, using the endophyte Heteroconium chaetospira, by Dr Hashiba of Tohoku University and Dr Narisawa of the Plant Biotechnology Institute.
Meanwhile, at the Institute of Physical & Chemical Research (RIKEN), Dr Arie has demonstrated the anti-auxin properties of epoxydon produced by Phoma glomerata (see Plant Pathology, 47 (6), 743-8). Opportunities for the study of the life cycle of P. brassicae using hairy- root culture has fascinated devotees of this organism for several years.
Further work using this system, was described by Dr. Kageyama of Gifu University. My contribution was in providing an overview of the host- pathogen relationship especially in relation to our research into the impact of calcium on plasmodial and sporangial growth in root hairs.
Life is not all science and the opportunity to revisit, for a weekend, the ancient (and modern!) city of Kyoto was too good to miss. The surrounding countryside still retains whispers of life prior to the Meiji Reforms of 1868. While within the City, the temples, bookshops and most of all the Botanic Garden (which was staging a fabulous Dendranthema (Chrysanthemum) Festival) offer endless pleasure.
My very sincere thanks go to my good friends Dr Seiya Tsushima and Dr Yoshiro Shishido for all their hard work organising the Clubroot Meeting, enabling me to participate and for many stimulating discussions and too many, many others for their hospitality and generous efforts in making this a most memorable fortnight.
Professor Geoffrey R Dixon, University of Strathclyde & GreenGene International
Detection, Isolation and Manipulation of Soil and Rhizosphere Microorganisms
Joint meeting of BSPP with the Society for Applied Microbiology.
University of Warwick _ 15-17 December 1998
This meeting was attended by some 80 delegates with an equal mix of well-established scientists and young enthusiastic post-graduate students. Weather conditions at Warwick were more like spring than winter (which was NOT the situation on the previous day in Aberdeen!)
The first day started with a review on "Microbes, in the rhizosphere and soil environment" by Richard Burns (University of Kent). This excellent talk tackled the enormous subject area by attempting to answer pertinent questions. Thus the question of what is the rhizosphere led to debate as to what is important, the microbes or their processes? In turn, the subject of how to deal with the enormous populations of viable but non-culturable organisms which are present and whether the rhizosphere can be manipulated to the benefit of man, were discussed.
In another comprehensive and interesting review Mike Daniels (John Innes Centre) discussed "Methods for the study of molecular mechanisms of bacterial pathogenesis". This talk made us aware that although 70 bacterial species have been fully cloned these include very few plant pathogens. This research area is also made more complex and stimulating by the fact that genes often show altered expression when bacteria are present in plants. Research still advances with more and more knowledge being gleaned in areas such as the understanding of the hypersensitive response and avirulence. The talk finished by illustrating a day in the life of xanthomonads in the xylem which showed that populations attain extremely high levels, presumably these bacteria must be starved of nutrients and this may explain why there are such high levels of extracellular enzyme production.
After tea break the day continued by a fascinating talk by Anne Osbourn, also of the John Innes Centre, on take-all and the cereal rhizosphere. This talk emphasised the role of avenacins in the disease.
Ian Barker (CSL, York) had the unenviable job of evaluating alternative technologies for detection and identification of microbes. He described cultural, serological, molecular and physical methods for disease diagnosis with great clarity using real agricultural and horticultural examples to illustrate the techniques. Interestingly, some of the more recently developed tests, using monoclonal antibodies or indeed recombinant antibodies, are proving valuable, not in replacing existing tests but by making them less tedious. The talk also discussed the correlation between the presence of a particular pathogen and its associated disease, bearing in mind that tests are becoming more and more sensitive.
Chris Gilligan (University of Cambridge) provided a clear and fascinating talk on mathematical modelling of environmental parameters that have an important influence on soil-borne micro-organisms and their interactions with each other, the host plant and the soil environment. Focusing mainly on Rhizoctonia infection of radish plants in the presence and absence of a Trichoderma biological control agent he used a combination of mathematics, statistics and experimental modelling of disease dynamics to show how small changes in pathozone behaviour can lead to variability in disease levels on a larger scale, give variability between replicate epidemics and account for inconsistent success in biological control studies. Making comparisons, of pathogen growth on the soil surface and through the medium of the soil, of size of soil aggregates and non-invasive spread and pathogen dynamics in the absence and presence of the biocontrol agent, Chris showed how the pathozone evolved, how this affected epidemics and secondary infection and how this was influenced by host plant density and the performance of the biocontrol agent.
Chris Thornton (Exeter University) focused on a particular pathogen, Rhizoctonia solani, to illustrate the use of monoclonal antibodies (MAbs) for the detection, quantification and retrieval of live propagules of the pathogen in field soils naturally infested with the fungus for the study of the effects of a biocontrol agent (Trichoderma harzianum) on growth dynamics of the pathogen in horticultural composts and for visualisation (using electron microscopy), of the pathogen in situ to gain insights into positional relationships and time sequences of events. MAbs were raised against a constitutive, extracellular, glycoprotein antigen secreted by actively growing mycelia. The presentation illustrated the various ways that MAbs could be combined with other techniques (microscopy, enzyme assays, hybridoma and nucleic-acid based technologies) to allow a multidis-ciplinary approach.
Day 2 focused on beneficial microbes with both symbionts and biological control micro-organisms being discussed. David Read (University of Sheffield) described advances in the detection, isolation and manipulation of mycorrhizal fungi paying particular attention to the methods that enable the role of these fungi to be evaluated in natural ecosystems. Numerous fungi may occupy the root system of a tree species and this "wood-wide web" captures nutrient resource at a distance, distributes it to the plant by the physiology of the fungus leading to selective proliferation of nutrient enrichment and subsequent nutrient allocation between plants. By selectively amplifying fungal DNA it had been shown that, in bluebells, 2 or 3 genera of arbuscular mycorrhiza are present. Mycorrhizal symbiosis is not always mutualistic and the fungus can have controlling influences and sometimes negative effects on the plant.
Penny Hirsch demonstrated how the use of strain-specific DNA primers
and PCR could be used to monitor rhizobium population levels by detecting
DNA extracted directly from field soils. With the use of nested primer
sets, rhizobia strains could be detected at fewer than 100 viable cells
per g field soil. The method could detect genetically-modified bacterial
inoculants in controlled release experiments down to 1-10 cells per g soil.
These methods should allow the acquisition of new knowledge concerning
survival and spread of rhizobial inoculants for improved nitrogen-fixation in relation to symbiosis with leguminous plants.
The role of pseudomonads as key plant associated bacteria that act as fungal antagonists and influence the microbial ecology of the rhizosphere was highlighted by Mark Bailey. Recent advances in molecular biology have allowed the interactive ecophysiology of natural isolates of fluorescent pseudo-monads and variants with improved activity against Pythium damping-off fungi to be studied. There is a common abundance of ribotypes in the rhizosphere and using site-directed mutagenesis (to avoid gene transfer) and marker genes (green fluorescent protein), constructs can be engineered to investigate antifungal activity in situ. Variants with improved activity and niche specialisation have been developed and some of these bacteria have similar nutrient requirements to the pathogen (Pythium) and displayed strong competition.
Frans de Leij described analysis of differential growth rates on rich
and poor media to give information on microbial communities in the rhizosphere.
Those organisms that grow fast and dominate nutrient rich, unstable environments
are sensitive to environmental stress and are poor competitors (classified
as r-strategists). Those micro-organisms that grow slow in nutrient rich
environments are relatively insensitive to environmental stress and are
characteristic of stable nutrient poor and crowded environments (classified
as K-strategists). It is possible to look at the distribution of different
"growth classes" on a r/K continuum by analysing communities on their ability
to grow on nutrient-rich and -poor agar. In this way r/K distribution is
expressed as an ecophysiological index describing
the "evenness" of r and K strategists within the soil or rhizosphere. An example was the effect of heavy metal contamination from Cu on the degradation of cellulose.
After lunch on Day 2, John Whipps looked at biological control of fungal pathogens in soils. John took us through the "blueprint" procedure for selecting, isolating and marketing a biocontrol agent. Problems of sequential scale-up in production and regulation and marketing procedures are important points and these must be dealt with. Emphasis was placed on the point that if biological control is to replace chemical fungicides then we need to know more about the ecological interactions between the biocontrol agent, the pathogen, the host plant and the environment in which we find them. These points were taken up with reference to the fungal mycoparasites Pythium oligand-rum and Coniothyrium minitans, their mode of action and interaction with the pathogen and the ecophysiology and influence of the environment.
Ken Kilham looked at bacterial biocontrol agents and the use of marker/reporter systems in elucidating in situ activity, colonisation and the effects of environmental conditions. Ken's group have chromosomally lux-marked bacteria (Pseudomonas corrugata R117 and Pseudomonas fluorescens B5) to look at antagonistic activity against Gaeumanno-myces graminis (take-all) and Pythium ultimum (damping-off) of wheat and pelargonium respectively. These workers investigated the influence of matric potential ranging from field capacity (-5kPa) to wilting point (-1500kPa) on the ability of the bacterial antagonists to suppress disease by the pathogen. It was shown that rhizosphere colonisation and disease control was affected. Ps corrugata could not colonise the wheat rhizosphere at stresses greater than -100kPa whereas Ps. fluorescens tended to show better colonisation and biocontrol activity under matric stress. Presence and activity of the antagonists were measured by charge-coupled imaging micro-scopy, a powerful in situ tool, with resolution ranging from the single cell to the population. CCD imaging indicated that colonisation towards the root cap by the antagonists was suppressed at matric stresses greater than -100kPa (i.e. under drier conditions). There was also evidence to indicate that grazing by predatory amoebae played a role in reducing population size of bacterial antagonists.
Finally, Mike Jeger lead a lively open discussion session on future
prospects and developments in the rhizosphere. Mike focused on two points:
(i) what is the rhizosphere? and (ii) organism vs. processes.
Some individuals were willing to accept a loose definition of what is the rhizosphere (David Ingram - "it's what you want it to be") whereas others suggested a precise definition was important to remove any misunderstanding. For this and for monitoring organisms and processes in the rhizosphere, Mark Bailey suggested that we accept we are dealing with a black box and should not worry too much about definitions and those aspects we know very little about as yet. Modern techniques (PCR, DNA profiling, monoclonal antibodies, CCD imaging) together with new approaches (ecophysio-logical indexing, survival vs. colonisation, predator-prey relationships) add further insights and twists to the story but take us deeper into our understanding of rhizosphere micro-organisms.
All in all, this was a most successful meeting. Questions and debate were not inhibited and those attending certainly got an up-to-the-minute report on the state-of-the-art. Many people suggested that the meeting should be recognised as a "first" and that the topic should be revisited every three years or so, something the organisers had not thought about at the outset! Many thanks from the organisers to all those who participated on the day or helped in the preparation and planning of the meeting, without whom the meeting would not have been the success it was. Eunice Allan would also like to express her thanks to the BSPP for an award from their Travel Fund which allowed her to attend this enjoyable and stimulating meeting.
Maybe see you all again in three year's time!
Eunice J. Allan and Barrie Seddon (Plant/Microbe Interactions Convenor SfAM)
University of Aberdeen
A conference I will never forget!
The Convention Center at Warwick provided a warm and welcoming venue for this Christmas meeting which was attended by a small but friendly group of about 60 participants. Richard Burns, from the University of Canterbury, set the stage by giving a broad overview of the activities and complexity of the interactions of pathogenic microbes in the environment of the rhizosphere and soils. This was followed by a talk from Mike Daniels who discussed the use of hrp genes and gene expression to study molecular mechanisms of bacterial pathogenesis. Take-all of cereals disease, caused by Gaeumannomyces graminis var. tritici, was discussed by Anne Osbourn. "Sad" mutants of oats, which vary in their abilities to produce avenacins, have been used to investigate their role in the interactions between oat roots and G. graminis var. tritici, avenae and other fungi.
The most interesting talks, for me, were the two dealing with detection and visualisation of fungi by Ian Barker. He mentioned the difficulties in producing a one-step device that is accurate as well as quick and simple. The potential of new techniques, such as the production of recombinant antibodies and "real-time" PCR were discussed. Chris Thornton showed how using a monoclonal antibody raised to antigens secreted by Rhizoctonia solani, which showed how amylase could be used to quantify and visualise the fungus in soils.
The meeting also included the BSPP-sponsored P.H. Gregory Paper competition and the Sfam-sponsored poster competition. Five people were selected for the paper presentation but only two brave women made it to the day; I cannot be very objective about it since I was one of them. There were about 20 posters on various topics. The wining poster was titled: "Physiological traits of rhizosphere bacteria in relation to supression of Pythium aphanidermatum on cucumber", by L.B Folman from The Netherlands.
The atmosphere at the conference dinner was very lively, particularly when David Ingram compared himself to the famous David Livingstone in a very amusing story. It was lovely and I enjoyed every minute of it specially when I got a very nice certificate, for winning the Gregory Prize, and a cheque of £250, just in time for Christmas shopping. I would like to thank the BSPP for funding my attendance at the conference - it was worth it!
Einat Reichert-Zelinger, Oxford Brookes University