BSPP News Spring 2001 - Online EditionThe Newsletter of the British Society for Plant Pathology
Number 38, Spring 2001
Conference and Travel Reports
Cereal Rusts and Powdery Mildews Conference
Budapest, Hungary : 28 August - 1 September, 2000
Hungarians have a strange verbal pattern when saying goodbye. Even when speaking Hungarian, when all goodbyes have been said, they suddenly say "Hallo". This can also be heard when they are finishing phone conversations. I understand that this may be spelled "Halo" in Hungarian, but it is used likewise when they speak English, and suddenly, just when you think the goodbyes have been said - "Hallo".
The conference was well organised, and ran according to a rather leisurely schedule, compared with some conferences I have attended. The relaxations included an afternoon of sight-seeing in Budapest, and a visit to the famous plant breeding and research institute at Martonvasar. The beautiful old house contains a museum of the visits, to the family who lived there, of Beethoven, and our visit included a very enjoyable recital of music from that time by young musicians. These events and the meal times gave plenty of time for personal contact in a conference having about 130 participants, from 28 countries. Some countries that had sent delegates to previous conferences were not represented, including India and Pakistan, China and Russia, and although scheduled to attend, nobody from Iran appeared.
The subjects of this series of conferences, held at four-year intervals, are many different aspects of the important group of obligate pathogens that infect cereals and related grasses, comprising the rusts and powdery mildews. These pathogens are responsible for large losses of yield of the major cereals when severe epidemics occur, as is still all too common. My own interest in them has been in relation to successful breeding of wheat and barley cultivars with inherited resistance that will prove to be durable in widespread cultivation. Perhaps because of my very long association with this organisation, I was asked to give one of two opening lectures, prefaced by a short history of how the system for organising the conferences came into being, which was a gradual process after the end of the second world war.
My paper was on the topic of the performance of the yellow rust resistance gene Yr18 believed to provide durable resistance. In New Zealand, Karamu, a carrier of this gene, had occasional self-sustaining and spreading infections, leading to the question of whether these were the result of rust isolates with virulence for the gene, or of favourable environments for disease development. The results were collected in New Zealand, Mexico and the UK. They showed that environment had a major effect, but that cultivars with Yr18 showed different levels of resistance, in which Karamu was among the more susceptible cultivars, Jupateco R was less susceptible and Thatcher lines into which the gene was backcrossed were the most resistant. There was no evidence for the occurrence of virulence for Yr18. I was therefore disconcerted, later in the conference, when one of my co-authors, S. Viljanen-Rollinson, presented further data from New Zealand on some of the lines, showing very different ranking, such that Jupateco R was among the most susceptible, and Karamu among the most resistant. This did not correspond well with the data I presented, which was partly obtained from New Zealand, and corresponded between all three countries in which the tests were conducted. There was no clear explanation for these new data, and they did not seem to tally with the occurrence of infections on Karamu in commercial plantings in New Zealand.
The other opening paper was given by K.-H. Kogel, Germany, on the identification and expression of genes induced in barley after chemical activation of disease resistance to powdery mildew. These included genes encoding a Ca2+-binding EF-hand protein, a serine proteinase inhibitor, an acid phosphatase, a fatty acid, a lipoxygenase, a thionin and several further proteins with as yet unknown functions. Their possible relationship to the well-known pathways mediated by salicylic acid and jasmonate in barley was discussed.
Topics covered in the conference included three main themes: Resistance Genetics and Breeding; Molecular, Biochemical and Physiological Aspects of Host-Pathogen Interactions; Population Diversity and Dynamics (of pathogens). Within this last topic, an interesting paper on the diversity of the leaf rust pathogens of cereals and grasses was presented by Y. Anikster from Israel, under the title 'A newly found leaf rust on Aegilops speltoides in Israel'. Apart from indicating a probable previously-undescribed formae speciales, the paper showed that there are two major groups of leaf rust pathogens, with different alternate hosts, one group having a sexual generation on Ranunculaceae, commonly on Thalictrum, the other on Boraginaceae, such as Anchusa, Echium and Lycopsis. The 'speltoides' type was related to Puccinia triticina with alternate host Thalictrum. This group also includes the leaf rust pathogen of wheat, often referred to as Puccinia recondita f. sp. tritici, but argued by some taxonomists to be correctly named Puccinia triticina Erikss. This is clearly a complex set of pathogens. Anikster argues that the two major groups have been sexually isolated from each other from ancient times and are evolving separately, and that some distinctive groups can be distinguished within the two main groups. Two papers about leaf rust of wheat used the name Puccinia triticina for the pathogen, whereas others used Puccinia recondita. As with many taxonomic problems, the final resolution of the correct name may take many years. I find these papers fascinating because they show an image of the way evolution has worked in these obligate pathogens that have such extraordinary life-cycles.
Also, in the same group of papers, an argument was presented that the powdery mildew of barley shows an increase in virulence complexity from West to East across Europe and Asia (E. Limpert, Switzerland). I heard some challenges to this proposal. In the paper, the author took the opportunity to describe his poster presentation arguing that the use of normal distribution for making statistical tests of biological variation may commonly be erroneous, because, he argues, much biological variation has a log normal distribution. If true, this means that relevant statistical differences may be missed in the lower end of a distribution. Of course, data transformation is usually used in attempts to equalise variances, but statistical tests using the log normal distribution could presumably be used without transformation if they did describe the type of variation occurring.
At least part of the recognised durable resistance to the leaf rust of wheat is believed to be controlled by the gene Lr34. Z. Pretorius (South Africa) described the phenotype produced by this gene on flag leaves of wheat, in which pustules of the rust are larger at the base of the leaf than at the tip. This could be related for the tendency for leaf tips of cultivars with Lr34 to become slightly necrotic and less favourable to a biotrophic pathogen.
I was interested to learn, in a discussion with J. Chong, Canada, that the very large number of genes named for resistance to Puccinia coronata in oats, far larger than the number named for resistance to each of the rusts of the much more important crop, wheat, arises in part from the much less rigorous data required for their designation than in wheat. Apparently the requirement for a gene for resistance to P. coronata does not include any need for tests of possible allelism with previously named genes. Some genes were even named as susceptibility genes - and nobody seems to know the meaning of this terminology.
Of course, there were many other points of interest in the presented papers and posters, but there has to be a limit to this report. It is proposed to hold the next of this series of conferences in England, probably in Norwich, in 2004 to be organised by James Brown of the John Innes Centre.
The Proceedings of the Conference were available at the conference and are published as Volume 35, numbers 1-4, 2000, in Acta Phytopathologica et Entomologica Hungarica. Copies can be obtained from Akadémai Kiado, H-1519 Budapest, P.O. Box 245, Hungary for US$196 and US$20 postage and packing. Unfortunately, the binding of the volume is very weak.
I wish to finish by thanking the BSPP and the organisers of the conference for financial support, enabling me to attend. Goodbye - Hallo.
Cereal Rusts and Powdery Mildews Conference
Budapest, Hungary : 28 August - 1 September, 2000
Budapest: the bustling heart of Hungary, dominated by beautiful bridges across the not so 'blue' Danube, thermal baths and paprika, and host to the 10th Cereal Rusts and Powdery Mildews Conference (CRMPC). A relaxed and informal atmosphere pervaded throughout this conference with scientific discussion outside of the lecture theatre playing just as an important role as the formal presentations. The scientific programme was dominated by work on rusts, with less emphasis on 'my favourites' the powdery mildews - perhaps a reflection of the intensive discussion these beasts received at the First International Powdery Mildew conference in Avignon, France last year.
Budapest explored 7 discussion sessions covering topics from host resistance and epidemiology, to disease control and physiological specialisation. Two opening lectures aimed at easing us into the conference before an 'intense' session of sightseeing, began with Karl Heinz Kogel highlighting the potential of induced resistance in future plant protection systems, with particular reference to barley resistance to powdery mildew. Roy Johnson's review of wheat resistance to yellow stripe rust, conferred by the Yr18 locus, was preceded by an interesting outline of the history of CRPMC.
Several common themes and 'take home messages' came through from the oral and poster presentations. A large emphasis was placed on the importance of breeding for resistance, as opposed to chemical control of the pathogen through fungicide application. Different types of host plant resistance were covered ranging from race specific resistance, as exemplified by Lr10, a wheat leaf rust resistance gene (Beat Keller), to partial and non-host resistance. Several lectures warned of the dangers of relying too heavily on major host resistance genes, which can easily be overcome by simple mutations in the pathogen population. Robert Parks illustrated how a single pathotype of wheat leaf rust, race 104, had spread, causing major epidemics from East to West Australia within the space of five years. This was the result of two single mutational events, which enabled the pathogen to overcome two major host resistance genes: Lr26 and Lr17b.
Breeding programmes aimed at achieving more durable resistance are required. The use of Quantitative Trait Loci (QTL) analysis to identify potentially more durable, minor resistance genes was reported by R. Niks, concerning work on barley leaf rust, while the potential of incorporating slow rusting and slow mildewing resistance into breeding lines was suggested by R. Singh. Singh additionally pointed out that with all these efforts towards breeding new resistant lines it is vital to test the stability of resistance under different environmental conditions. The potential benefits of combining adult plant resistance and seedling resistances in a single breeding line were presented not only for crown rust by James Chong, but also towards yellow stripe rust by Lesley Boyd.
With any plant breeding strategy it is important to have a good understanding of the genetic basis of the host-pathogen interaction. James Brown, in one of only a few talks dedicated to powdery mildew, gave examples of variations on the classical gene-for-gene relationship, in addition to detailing the comprehensive linkage map for Blumeria graminis f.sp. hordei, constructed by his group.
The use of molecular techniques in studying population diversity and dynamics were presented by several authors. DNA Sequence and AFLP analysis are being exploited to identify new, and monitor the spread of existing, pathotypes. This was illustrated by Hovmoller's work on the evolution of populations of Puccinia striiformis f.sp. tritici in Northwest Europe. It is important that modern molecular methods are used in conjunction with traditional methods of identification, based on host range and morphological characteristics e.g. spore dimensions (as presented by Yehuda's classification of a new leaf rust on Aegilops speltoides in Israel), to obtain a more comprehensive classification of the pathogen. My own work on the molecular evolution of host specificity in wild grass powdery mildew attempts to achieve this with some very interesting results concerning the formae speciales system.
All of the themes were enhanced by around 30 posters covering many other aspects of cereal rust and powdery mildew research. The scientific and social programmes intermingled with an interesting half-day excursion to Hungary's most notable breeding station at Martonvasar. Here the delegates had the opportunity to learn about the history of the country's wheat breeding programme and the facilities available today, as well as enjoying the beauty of the grounds and ornamental lake surrounding the station.
I would like to thank BSPP for their generous financial assistance towards my attendance at this conference, which was additionally supported by the International Botanical Congress Fund Edinburgh. It enabled me to present my work orally, broaden my knowledge particularly in the area of rust pathology, and convert some of my e-mail correspondences into friendly faces.
John Innes Centre, Norwich
The11th MBFP took place in sunny Norwich... at the University of East Anglia and the John Innes Centre (Norfolk, UK). As last year, there were around 100 participants, mainly postgraduate students and post-docs, of which a large number were able to present their work and stimulate new discussions on the many different approaches applied to the study of plant-fungal pathogen interactions.
The first session covered the infection process of Magnaporthe grisea. Darren Soanes (Exeter) presented his work on MPG1 using a GFP construct to study expression of the MPGI promoter. The second presentation, by Pascale Baldhadere (Exeter), described the screening of REMI transformants on barley cut leaf assays for penetration deficiency followed by the isolation and study of the PDE1 gene. Marie Dufresne (Sainsbury Laboratory) ended the session with a talk about the genetic components required for proliferation of M.grisea in distinct plant tissues (leaf/root).
The second session focused on pathogenicity, beginning with the expression of a biotrophy related gene, CIH1, in Colletotrichum lindemathianum. Katherine Pixton (Birmingham) looked at the expression of a ClH1/GFP construct under different growth and biotrophy conditions. Alexandra Collins (HRI) presented her results on the origins of different crucifer isolates of Verticillium dahliae using RFLP and ITS sequence analysis, which had allowed the identification of four separate groups. The following talk was presented by Morgane Guilleroux (Sainsbury Laboratory) on In planta expressed genes in the interaction between Gaeumanomyces graminis and cereals at the early stage of infection using a subtracted library. The last talk of this session by Bleddyn Hughes (Sainsbury Laboratory) summarised the latest results on the detoxification of oat avenacosides (antifungal molecules) by Stagnospora avenae.
The talks on Thursday morning covered different ways to study host specificity. Rebecca Wyand (JIC) investigated molecular host specificity in wild grass powdery mildew by screening a collection of isolates by ITS sequencing. The next speaker was Anne Rehmany (HRI). She presented results on a map-based cloning strategy for the isolation of an avirulence gene from Peronospora parasitica (a pathogen of Arabidopsis thaliana). The final talk, by Stephen Whisson, (HRI) also showed the use of map-based cloning and results of a subtracted library to identify pathogenicity factors and avirulence genes in Phytophthora infestans.
The second morning session included talks on detection and population studies. Chris Thorton (Exeter) described ways of using antibodies to track Rhizoctonia and Trichoderma in soil. The other talks were all on PCR based methods: Adrian Turner (JIC) has quantified wheat stem base disease agents in field trials by quantitative competitive PCR, Nicholas Gosman (JIC) also used quantitative PCR of fungal DNA as a mean of identifying wheat varieties that are resistant to Fusarium head blight and foot rot, and Beatrice Henricot (RHS, Wisley) used specific PCR amplification of GP42 (cell wall protein) to detect the genus Phytophthora.
The last two talks of the main sessions took place on Friday morning on the effects of host factors on fungal pathogens. Hannah Johnson (Imperial College) has been looking at plant disease resistance by studying the effect of reactive oxygen species on C.fulvum, and Senga Kyle (SAC Auchincruive) presented her study on the effects of essential oils on fungal gene expression.
All of the longer talks presented new and interesting results from a wide range of fungal pathogens, along with the application of many different techniques to study plant-pathogen interactions. Four workshop sessions provided an overview of starting a project and the difficulties that could arise in the lab from using these different methods. By presenting a 5-10 minute talk, many students had the opportunity to stimulate open discussion on problems they might meet during their Ph.D., and to receive advice from more experienced people. 'Pathogenicity and infection', 'Diagnostics and diversity', 'Avirulence and genome organisation' and 'Testing gene function' were the themes of these sessions, which covered a lot in terms of plant-pathogen interactions.
There was no invited speaker from industry this year for the main talks but during the short sessions Zeneca scientists were able to demonstrate their facilities on site at the JIC with a special tour of the new laboratory. Also, Nick Talbot (Exeter) summarised the national situation in the field of fungal pathogenicity and made clear the need to choose one particular fungus as a model for sequencing analysis.
The meeting was not as sporty as the previous year. Even the heated swimming pool at the JIC could not tempt many for a splash on Thursday night. This was probably due to the attraction of the bar which was open at the same time.... The first evening's entertainment was more cultural, with a reception and a private view of the Sainsbury Centre of Visual Arts, which ended up in the bar at UEA after a really nice conference dinner. On Thursday night, we had the chance to know everything on how to brew beer or more precisely "Barley to beer: the last 4000 years of brewing science..." by Chris Ridout - very interesting talk but samples were missing... The evening carried on with a buffet dinner and a special disco where the DJ was James Brown himself!!
People seemed to enjoy both the main session and the short talks. The workshop summaries on Friday morning informed people about the sessions they did not attend. The informality of this meeting is much appreciated as it allows everyone to voice their opinion without feeling intimidated. Next year, MBFP will take place in Gregynog and many thanks again to The Gatsby Foundation, the British Society for Plant Pathology, Zeneca Agrochemicals (and Zeneca scientists for their contribution to the workshops) and the John Innes Foundation for their generous sponsorship of this meeting.
Sainsbury Laboratory, Norwich