Plant diseases threaten global food security and cause losses of billions of Euro to the EU economy each year. Disease control by pesticides is often not possible, e.g. in the case of bacteria or soil-borne pathogens, is in general not durable due to the emergence of pesticide resistance in pathogens and raises continued ecological concern. In 2009, the Directive 2009/128/EC was adopted which requires member states to “take all necessary measures to promote low pesticide-input pest management”. The use of disease resistant crop varieties constitutes the economically and ecologically most viable alternative to pesticides in plant pest control. Unfortunately, the current number of resistance genes in major food crops is limited, while their action spectrum is often restricted to individual strains of pathogens. More worrying, from an agronomic point of view, is the ability of pathogens to accelerate their rate of evolution in response to the high selection pressure imposed by resistance genes, which frequently results in rapid breakdown of plant resistance. Break-down of resistance can occur after only a few growing seasons and is difficult for plant breeders to estimate the agronomic lifespan of a resistance gene without prior knowledge of the matching effector. Consequently, breeding for durable disease resistance in crop varieties by trial and error is slow and costly.
The impact of genome sequencing
The genomes of the most important pathogens of cereals and solanaceous plants have been sequenced and were published during the last five years, generally in extremely high impact journals. These projects have been conducted by international consortia and European researchers and European research funds were generally of key importance.
This on-going sequencing of pathogen genomes is revolutionizing plant pathology and is generating for the first time the insights into the molecular and evolutionary mechanisms of pathogen virulence, necessary to efficiently breed or engineer for durable disease resistance. The availability of whole genome sequences has enabled progress in the identification of pathogen molecules involved in evading or breaking disease resistance and plant-pathogen interaction research has strongly shifted to the investigation of pathogen virulence effector proteins and their mode of action in host plants.
Effector proteins are secreted by pathogens during infection as key elements in disease and resistance. They are essential for virulence as they allow pathogens to manipulate host immunity and physiology in favour of infection. They are also central to resistance as their recognition in resistant plant varieties triggers strong defence responses preventing disease development. Pathogens can escape host recognition through mutations that modify or delete effectors. Depending on the fitness penalty (i.e. the reduction of virulence) associated with such mutations, resistance breakdown in the field and subsequent successful spread can occur rapidly or more slowly. The availability of increasing numbers of whole genome sequences is starting to generate lists of candidate effectors for major pathogens and will further help to understand the role of genome structure and plasticity in the adaptive evolution of pathogens. They are the basis of innovative, pathogen-informed strategies for durable and broad spectrum crop resistance that are emerging
The goal of the Action is to exploit latest knowledge on plant immunity and pathogen virulence for the generation of wide spectrum and long-lasting plant resistance. This will be achieved through two major lines of development and innovation:
- The identification of new resistances (resistance loci/traits) in plant germplasm collections.
- The evaluation of resistance durability by the detailed analysis of pathogen effector proteins in light of their dual role as central players in pathogen virulence and plant resistance protein targets.
Knowledge on durable resistances will be transferred to European plant breeders for the generation of durably resistant crops based on innovative non-GM approaches that will enable sustainable agriculture in Europe and developing countries. In addition to directly contributing to the development of durably resistant crops, the Action will intensify the transfer of concepts and results from academic research to European plant breeders. It will network European research groups in the field to intensify exchange of ideas and people to coordinate future research.
For additional information, please refer to the Memorandum of Understanding