Pseudomonas savastanoi as an emerging pathogen: Genomics and evolution of host specificity. Pseudomonas syringae pv. phaseolicola pathogenomics

Understanding of the molecular basis of host specificity in bacterial phytopathogens is pivotal for the development of effective management strategies that minimize the use of pesticides and exploit plant host resistance. P. savastanoi pv. savastanoi (Psv) produces aerial tumours on the host, causing one of the most important diseases of olive, but was shown to cause disease in a plethora of plant species. Control of Pph is desirably carried out using resistant bean cultivars. Isolates of Pph are classified into nine races based on their interactions with a set of eight differential bean cultivars, although further differentiation is possible for up to at least fourteen races and five pairs of resistance and effector genes have been postulated to explain part of the gene-for-gene interactions. These two pathosystems offer an unprecedented opportunity to study the molecular basis of pathovar definition. Pph is a genetically highly clonal pathovar, although it shows a range of pathogenic variation underlying race-specificity. The availability of closed genomes for the model strains Pph 1448A and Psv NCPPB 3335, as well as the genetic and functional tools developed in previous projects, make these bacteria ideal candidate models for the analysis of host-range definition and the evolution of virulence.