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BIOlogie et GEstion des Risques en agriculture - Champignons Pathogènes des Plantes


"Integrated Strategies for the management of stem canker of oilseed rape in Europe" (IMASCORE)
Partners : INRA Versailles, FRA (coordinator) (contact : mhb@versailles.inra.fr), ISA Lisbonne, PT ; UNI Göttingen, GER ; IACR Rothamsted, UK ; CETIOM, FR ; IGR Poznan, POL ; DSV, GER ; Cargill/Monsanto, FRA

Objectives and main results:

The general objective of this project was to propose integrated strategies to control this pathogen. Such strategies relied on (i) the obtainment of new data on this disease, both on the plant and the pathogen sides, in the European context, and (ii) the development of tools which can be used for the management of the disease. Mainly, it was planned to obtain : tools for a survey of populations of the pathogen; standardised protocols as well as reference isolates and an extensive differential set of Brassicas for the assessment of the interactions; new resistance genes and molecular probes for the characterisation of these genes. The main species and races of the L. maculans species complex were to be characterised and mapped at the EU scale and models for risk forecasting were to be developed. In the longer term, Elite varieties integrating the new resistance genes should be obtained and commercialised at the European level.

To meet these objectives, we firstly had to clarify what is termed L. maculans in Europe by comparing a wide range of European isolates with a world-wide collection of isolates. We studied the epidemiology of the pathogens and compared it under three different European climates. New sources of resistance were looked for in B. oleracea, B. rapa and B. napus core collections, by screening with isolates representative of European races, in order to diversify the useable resistance in oilseed rape. The efficiency of newly-released resistant varieties or lines was evaluated under field conditions and was related to both population structure and epidemiological data. Genetic bases of the interactions were analysed on both the plant and pathogen. Specific probes for a further survey of pathogen populations were developed for two main races of the pathogen. The definition of the genetic control of resistances, along with data regarding population structure and epidemiology, were used to design integrated strategies for the control of the disease at the European scale. The IMASCORE programme lead to major progress in the following areas : (i) the geographic repartition of the L. maculans species complex was established at the whole Europe scale, while more and more data have been obtained that indicate rapid shifts in population structure at the race level, (ii) field resistance assays set up in three different countries stressed the importance of multilocal assessments of resistance, (iii) genetic studies on the plant and pathogen sides provided clear evidence that gene-for gene interactions is the rule in this pathosystem, (iv) many new data were obtained regarding the epidemiology of the pathogen, under field and controlled condition. Data on disease development, pseudothecia maturation, ascospores release and weather data have been collected for three years of field epidemiological survey in the UK, France and Poland. Key epidemiological parameters for pseudothecia maturation, ascospore release, and leaf infection (in terms of temperature and leaf wetness duration) were determined and are the basis of the SECURE programme. (v) Data on seed transmission of the pathogen, as well as on the extent of fungicide action within the infected plant were also obtained. (vi) All the tools and new knowledge developed during the programme now constitutes a steady basis for future management of the disease.