Bacterial spot caused by Xanthomonas vesicatoria devastated tomato production of Khyber Pakhtunkhwa-Pakistan

In Khyber Pakhtunkhwa (KP) province-Pakistan, bacterial spot caused by Xanthomonas campestris pv. vesicatoria (Xcv) has decimated commercial tomato production. Field surveys were conducted in 2017 and 2018 to analyse the effects of the bacterial spot in tomato producing areas of KP, including Swat, Lower Dir, and Mansehra. During the growing seasons, diseased samples were collected from tomato fields, and disease incidence and severity were documented. The pathogen was isolated, purified, and morphologically and biochemically characterised. Most of the morphological and biochemical characteristics such as yellow colonies, were like those of Xanthomonas spp. Further, the pathogen was confirmed using XV1F/XV1R pair of species-specific primers, which amplify the atpD gene sequence solely in Xanthomonas vesicatoria. Out of 30 isolates, 16 isolates were confirmed to be Xcv. In these agro-ecological zones, this was the first report on the presence of Xcv. Furthermore, humidity and temperature were found to impact the incidence and severity of bacterial spot substantially. Most isolates grew at high temperatures and low humidity; however, some prefered high-temperature and low-humidity environments. In conclusion, bacterial spot disease caused by Xcv has now spread throughout all tomato-producing areas of KP province. To avert future plant epidemics, ongoing climate and pest monitoring is required to build an effective disease warning system for producers and other agriculture-related agencies.