Host range and virulence diversity of Pectobacterium carotovorum subsp. brasiliense strain RDKLR infecting radish in India, and development of a LAMP-based diagnostics.

Aim: This work aimed at determining the pathogenicity, molecular characterization, host range and rapid detection of Pectobacterium carotovorum subsp. brasiliense (Pcb) causing soft rot disease in radish.

Methods And Results: The four isolated isolates were inoculated to radish, typical soft rot symptoms were observed and Koch's postulates were proved. The most virulent strain RDKLR was morphologically and biochemically distinct. Pcb showed a positive potato soft rot test and elicited hypersensitivity response on Nicotiana tobaccum. The genes Pel2 and pmrA were used for subspecies characterization of Pcb. It has a wide host range and infection was observed on slices of carrot, tomato, radish, potato, cauliflower, cabbage, chilli, knol-khol, bell pepper and cucumber. Infectivity was also seen in seedlings under glasshouse conditions. Pcb produced cell wall degrading enzymes in semi-quantification assay and is a strong biofilm producer. The LAMP technique was standardized to help rapid detection and take prophylactic measures to manage the disease.

Conclusion: This work reports Pcb as a new soft rot causing organism of radish in India. Pcb is highly virulent with a broad host range. The LAMP technique helps in rapid detection.

Significance And Impact Of The Study: Pcb-induced soft rot causes significant yield loss, decreased market value, damage in transit, storage and the market. Disease characterization and early identification aid in disease management and prevention in the field.