Pseudomonassyringae pv. actinidiae (Psa) is a gram-negative bacterium responsible for the bacterial canker in Actinidia chinensis var. deliciosa and A. chinensis var. chinensis, a quarantine organism threatening the kiwifruit industry sustainability. The present study aimed to determine the genetic structure of the endophytic and epiphytic populations of Psa isolated from four different Portuguese orchards with distinct abiotic conditions in two consecutive seasons. The results identified several coexisting and highly heterogeneous Psa populations. Moreover, evident changes in population structure occurred between the epiphytic and endophytic populations, and between seasons with a notable decrease in Psa diversity in autumn. This work provided solid evidence that the initial clonal expansion of Psa in Europe was followed by a wide genomic diversification. This perspective is important for the understanding of kiwifruit bacterial canker disease occurrence and Psa evolution, namely when adopting strategies for management of epidemics.

Pseudomonas syringae pv. actinidiae is a quarantine bacterium affecting all the Portuguese main areas of kiwifruit production. We report the draft genome of six P. syringae pv. actinidiae strains isolated from symptomatic leaves of Actinidia chinensis var. deliciosa in a study that determined the genetic population structure of the endophytic and epiphytic populations in two consecutive seasons. Average nucleotide identity values were above 99% similarity with reference strains from P. syringae pv. actinidiae biovar 3. The genomic differences found between these strains confirm the genetic diversity described for P. syringae pv. actinidiae population in Portugal. Furthermore, data provide evidence that the initial clonal expansion of P. syringae pv. actinidiae in Europe was followed by a genomic diversification constituting a valuable resource for epidemiological and evolutionary studies, namely when adopting strategies for epidemics management.