Host range and survival studies of bacterial leaf spot of green gram pathogen Xanthomonas axonopodis pv. Vignaeradiatae

Bacterial leaf spot pathogen Xanthomonas axonopodis pv. vignaeradiatae produces symptoms on leaves, stems, pods and seeds. Small water-soaked spots are the initial symptoms observed on leaves and appear within 4 to 10d of infection. Bacterium was tested on 20 different plant species by inoculating one month old leaves using carborundum abrasion technique and the disease development was recorded. Out of the twenty plant species, the pathogen could produce visible symptoms on Black gram (Vigna mungo), cow pea (Vigna sinensis) and cluster bean (Cyamopsis tetragonoloba). This study indicated that sensitive plant species may be collateral hosts of this pathogen and it has narrow host range. In host age studies, the PDI decrease with increase in age of green gram plants after attaining the maximum severity at 30d stage. In plant debris, the survival period of pathogen was maximum (480d) in refrigerator and minimum (40d) in outdoor conditions. The bacterium survived longer (570d) in seeds, when soaked in bacterial suspension and stored in refrigerator.