Projects

The major airborne cereal diseases in most of the European cereal growing areas are powdery mildews and rusts. These diseases can be controlled in an economic and ecologically safe manner by cultivation of resistant varieties. However, as successful varieties become widely grown, populations of the mildew and rust pathogens adapt to them. This may lead to heavy attack by disease, which then needs to be controlled by fungicides. The present extensive use of fungicides may present an environmental hazard, and involves large and unpredictable expenditure by farmers. If we were able to understand the behaviour of the mildew and rust populations better, and could therefore make better predictions as to the performance of resistant varieties and fungicides, we could reduce the need to use fungicides to control these diseases. This would reduce both environmental hazards and farmers’ costs.

At present, the same resistance genes and fungicides are used in many European countries and, since mildew and rust fungi are easily spread across Europe by wind, Europe-wide selection in favour of virulent and fungicide resistant fungal genotypes takes place. National survey programmes have been set up in many European countries in order to monitor changes in virulence frequencies and fungicide sensitivity. The main aim of these programmes is to ensure an effective use of resistance genes and fungicides on the national scale. There is a need to improve and co-ordinate the efforts made in the national programmes because of the Europe-wide scale of the issue, as well as to provide a rapid flow of information among the countries. Further, the information from the surveys is at present insufficient on a European scale due to the lack of generally accepted differential cultivars and standard methods for analyses of fungicide sensitivity.

In addition to monitoring the pathogen population, there is a need for reliable and comprehensive information on the presence of resistance genes in commercial varieties in order to help breeders to select the most efficient combination of resistance genes and farmers to grow the most resistant varieties. Further, the improvement of strategies for Europe-wide use of resistance genes, integrated with the use of fungicides, will increase the time period of successful use of resistance genes and fungicides, while reducing the environmental load of cereal production.

To achieve these goals, a detailed knowledge of pathogen populations across Europe is required concerning among other things: how the fungal spores are spread; which selection forces influence the pathogen populations; how these selection forces can be changed by better strategies for the use of resistance genes and fungicides; the frequency of mutations and sexual recombination in the pathogen; how these mechanisms influence the appearance of new pathotypes and how molecular markers can be used for improving our understanding of the genetics of host plant resistance and of pathogen virulence, aggressiveness and fungicide sensitivity. In addition, improved knowledge of the host populations is required, including: identification of the resistance genes present in pre-competitive lines and commercial varieties of barley and wheat and analysis of non-race-specific resistance. Research and development is taking place on these subjects in the countries involved in this project and this research, in many cases, has a worldwide reputation.

The present Action will have contact with the few international initiatives concerning co-ordination of pest control in general such as:

1. The European and Mediterranean Plant Protection Organization, EPPO, which is mainly concerned with quarantine questions and with guidelines for testing and use of pesticides and not directly involved in co-ordinating research;
2. The International Organization of Pest Resistance Management, IOPRM, which is promoted by the United States, but not finally established; this initiative focuses on pest management in non-industrial countries and mainly involves people from government and industry. The present Action is much more specific and concentrates on co-ordinating research activities and on controlling major European cereal pathogens; and
3. The European Cereal Rusts and Powdery Mildews Foundation, which is a small, private organization, with no finances, offices or staff. Some of the results of the action are intended to be published in the Bulletin published by this organization and to be presented at the conference which it organizes every fourth year.

2. OBJECTIVES OF THE ACTION

The action aims at co-ordinating national research on improving integrated strategies for use of host resistance genes supplemented by fungicides to control pathogens spread by wind throughout Europe. Thus, it supports European agriculture in its attempt to produce healthy and high quality cereal crops at a low input and it aims at changing agricultural practice towards environmentally safer production. The action concerns the major cereal pathogens in Europe, powdery mildews and rusts, and has the following objectives:

• to co-ordinate national surveys on virulence and fungicide resistance as well as analyses of pathogen population data;
• to compare and, where necessary, to standardize methods, e.g. assessment of virulence, aggressiveness, fungicide sensitivity and definition of DNA markers, so that results from different laboratories can be integrated;
• to co-ordinate definitions and national monitoring of host resistance genes;
• to improve strategies for management of host resistance genes supplemented by fungicides and co-ordinate national recommendations;
• to establish regular expert meetings and an information system to ensure a rapid and effective exchange of information to scientists, breeders and farmers.

The co-ordination is expected to be built up during a five-year period with two main tasks, surveys and comparison tests. National surveys take place every year and in the first year results from these can simply be put together. Based on discussions of sampling strategies and studies of population structure, a European sampling strategy may be defined, and by the end of the project a procedure for regular reports on changes in the European pathogen populations should be defined. Along with this should go reports on the use of host resistance genes and fungicides, including the use of diversification schemes such as variety mixtures. Finally, based on mathematical models, attempts will be made to predict changes in the pathogen populations. The data will be communicated adequately, e.g. by the Bulletin of the European and Mediterranean Cereal Rusts and Mildews Foundation or by other journals of relevance for science and practice.

In addition to studying the response of pathogen populations to different strategies of using resistance genes and fungicides, the studies of pathogen populations will be used to optimize strategies for the use of host resistances and fungicides. An obvious example is in the prediction of which variety mixtures will be most appropriate for a particular region at a particular time.

Comparison tests will take place for the major pathosystems at least twice. Selected isolates will be exchanged among laboratories for testing, together with seed of differentials. The results will be collected and analysed and definition of methods and genes should be agreed on. An important part of this is to define appropriate differential sets for assaying virulence genes and to compare and, where necessary, standardize methods for measuring aggressiveness and fungicide sensitivity. If possible, the results of such tests should be published in scientific journals.

3. ORGANIZATION AND MANAGEMENT

The Management Committee (MC) will meet two to three times each year, preferably in local laboratories, to treat the subjects relevant to the objectives of the action. Preferably, one delegate from each country should participate in all MC meetings to promote continuity and successful co-ordination. The second delegate could vary depending on the main subject of a particular MC meeting.

Further, one person for each major pathosystem and trait, preferably an MC member, should be chosen for a specific period as responsible for the co-ordination and the reporting of the results.

Two or three workshops will be held where the research of importance for the project is presented and the results of the co-ordination can be discussed in a broader forum.

General Information: Current status

At the Management Committee meeting in Grignan (F), March 1995, H. ØSTERGÅRD (DK) was unanimously re-elected as Chairperson and J. BROWN (UK) as Vice-Chairman. At present the work is done within six Working Groups of which WG6 was formed at the MC meeting in Cambridge (UK) in December 1995, and WG4 was renamed at the MC meeting in Lunteren in September, 1996 :

• Working Group 1 : "Surveys on virulence, aggressiveness and fungicide resistance", (Co-ordinators : P. Bartos, CZ , R. Bayles, UK, V. Caffier, F, J. Clarkson, UK, G. Kema, NL, U. Walther, D)
• Working Group 2 : "Variety and species mixtures to control airborne diseases of cereals", (Co-ordinators : M.S. Wolfe, CH, M.R. Finckh, CH)
• Working Group 3 : Cereal rust and mildew genome database" (Co-ordinator : H. Giese, DK)
• Working Group 4 : "Host resistance especially partial resistance", (Co-ordinators : R. Niks, NL, H. Skinners, N)
• Working Group 5 : "Epidemiological parameters" (Co-ordinator : C. Vallevaielle-de-Pope, F)
• Working Group 6 : "Fungicide sensitivity" (Co-ordinators : F. Felsenstein and B. Nielsen)

Since the Action began in February 1994 European scientists working on powdery mildew and leaf rusts of wheat and barley and wheat yellow rust have been brought together. Another disease, wheat leaf blotch, has been included from late-1996. The emphasis has been on co-ordinating methods of testing, modelling and surveys of the pathogens which cause these diseases, so that data from research in different countries can be compared and used by scientists across Europe.

Scientific and technical progress :

• we have developed core differential sets of varieties for research on wheat rusts, to allow comparison of virulence assays in different European countries ;
• we have recommended a standard nomenclature for resistance genes which has been agreed by scientists, breeders and test authorities in countries taking part in the Action ;
• we have set up "blind" ring tests of fungicide resistance in barley mildew so that results of future research in different European countries can be more easily compared ;
• we have set up an Internet database, called PATHOGENES, with molecular marker and virulence data on barley mildew from several laboratories in the Action. This is connected to GRAINGENES,
• database on cereal genomes. Information on resistance genes has been contributed to GRAINGENES by this Action ;

co-operation between laboratories (e.g. 17 Short Term Scientific Missions 1995/96) in the Action has led to scientific advances in our understanding of :

• the genetics of avirulence of barley powdery mildew ;
• the influence of density on epidemiological parameters ;
• short-range and long-distance dispersal of pathogen spores ;
• comparative evolution of cereal mildew in Denmark and France ;
• the effect of leaf stage on epidemic development of cereal mildew.
• An e-mail bulletin board has been set up, to facilitate communication between participants in the Action.
• An Internet home page describing the Action (objectives, status, participants, new results, technical picture gallery, meetings) has been set up.
• Work planned: Working Group 1 plans in 1997 to produce the first European Survey Report on Rusts and Powdery Mildews.

Source: European Commission