How can we achieve durable disease resistance in agricultural ecosystems?

McDonald BA.

New Phytologist 185: 3-5, 2010

Plant pathogens evolve rapidly in agricultural ecosystems. It is likely that this fast pace of evolution is connected to the nature of the agroecosystem, which is dominated by genetically uniform species monocultures grown at a high density and on a vast scale. Mounting evidence indicates that many pathogens emerged over the last 10 000 yr during domestication of the affected crops and that new pathogens emerge regularly in these human-engineered ecosystems (Gibbs et al., 2008; Stukenbrock & McDonald, 2008). While the rapid pace of pathogen evolution presents a major impediment to sustainable food production, it also provides interesting opportunities to better understand the evolutionary biology of host–parasite interactions. Pathogen evolution is usually inferred after resistant crop cultivars deployed in farmers’ fields suddenly lose their disease resistance. This ‘breakdown’ of resistance has been observed many times around the world over the past 100 yr. Less commonly, pathogen evolution is observed in carefully controlled field or glasshouse experiments, that is, through experimental studies of evolution. Two French groups recently used serial passage experiments to show that plant viruses can rapidly evolve virulence against resistant cultivars (Chain et al., 2006; Palloix et al., 2009). A New Phytologist article by Brun et al. (this issue, pp. 285–299) presents a landmark study in experimental evolution of a fungal plant pathogen that offers a proof of principle for an important concept, the blending of different forms of genetic resistance to provide long-lasting disease resistance.

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