Bacterial speck of tomato is caused by Pseudomonas syringae pv. tomato (Pto) and occurs worldwide. It is generally believed that Pto is transmitted by seed and survives on asymptomatic weeds. However, very little research has been done during the last 30 years to further investigate how Pto is transmitted. Moreover, it is still unknown where in the world Pto originally emerged. Using whole genome sequencing we are trying to identify geographic origin and international routes of transmission of Pto. Based on the Pto genomes sequenced so far, it is clear that Pto moves frequently between North America and Europe and occasionally between the northern and the southern hemisphere. Interestingly, one lineage of Pto was identified in a creek in New Zealand upstream of any agricultural activity suggesting that Pto may be able to move long distance not only by seed but also through the water cycle and precipitation and surface water may possibly be inoculum sources of Pto