Incidence and transmission of Xanthomonas axonopodis pv. vesicatoria in tomato (Solanum lycopersicum L.) seeds grown in Rajasthan

Background- Tomato (Solanum lycopersicum L.) of family Solanaceae is one of the most globally consumed vegetable crop. Aim- A survey was conducted to study the bacterial diseases incidence in crop. Method-Dry seed examination of 75 seed samples of tomato belonging to 13 districts of Rajasthan revealed 10-100% incidence of Xanthomonas axonopodis pv. vesicatoria (XAV) on Tween-80 (semi-selective medium). Two naturally infected seed samples of tomato carrying 100% incidence of XAV were selected and categorised into asymptomatic, moderately discoloured and heavily discoloured seeds. Results- The heavily infected seeds were shrivelled with or without pseudo-hairs or water-soaked symptoms on seed surface; on bisecting such seeds the embryo and endosperm showed necrosis and browning. Such discoloured seeds on incubation yielded colonies of XAV. The cultural, biochemical and pathogenicity tests were carried out for identification of the bacterium. For the transmission studies, Petri plate method, water agar test tube seedling symptom test (TTSST), pot experiment and field studies were carried out. In the pathogenicity test, stab inoculation, smoother of seeds with pathogen and inoculation of fruits by pure culture were tried.