Plant pathogens: how can molecular genetic information on plant pathogens assist in breeding disease resistant crops

Numerous phytopathogenic fungi and Oomycete species cause disease on crop plants. Over the past 17 years a combination of protein purification and forward and reverse genetics has lead to the identification of > 150 distinct pathogenicity and virulence genes required by pathogens to cause disease. Many conserved molecular mechanisms are now recognised that underpin the pathogenesis of very diverse species. In addition, > 20 pathogen effectors have been characterised which activate either non-host or race-specific resistance (R) gene mediated plant defence responses. Recently, full genome sequencing projects have been completed for eight phytopathogenic eukaryotic organisms and others are in progress. Through comparative genome analyses, the gene inventory and genome synteny of animal and plant pathogenic fungi and Oomycete species are being compared with each other and with other nonpathogenic organisms. This is providing exciting new information on the evolution of plant pathogens. For plant breeders, this wealth of molecular genetic information provides the opportunity to develop a suite of new approaches to attain durable disease control. For example, many pathogen targets have been revealed which potentially are accessible for intervention via plant cell derived products. Also, there is now the unprecedented capacity to monitor changes in plant pathogen populations resulting from the introduction of different resistant plant germplasms. A case study involving Fusarium graminearum and F. culmorum, which cause ear blight disease on wheat and other small grain cereals, is presented and illustrates how crop breeding can be assisted by molecular genetic information on the pathogen. Media summary Gene inventories and gene function tests for organisms causing disease provide breeders with unique information to help identify and deploy new sources of durable resistance.