Abstract

Studies on the nature and extent of bacterial inoculum in storage godowns of onion revealed the occurrence of E. carotovora var carotovora in rootlets, gunny bags, godown sweeping and leaf debris and infected bulb in the field which may serve as source of inoculum. E. carotovora var carotovora survived better in the combination of sterilized soil + leaves + bulbs, which retained more number of bacteria even after six months of inoculation. Half of the inoculum load was detected in the unsterilized soil + leaves + bulbs. Studies on the detection of seed-borne nature of bacterium revealed that bacterial oozing from seed contains E. carotovora var. carotovora. Polyclonal antibodies were raised against unfractionated protein of E. carotovora var. carotovora. Indirect ELISA was carried out to detect the antigen and it was found that 1:1000 dilution of antibodies was necessary to detect the antigen. Seed treatment with Pseudomonas fluorescens FP7 was effective in checking the seed-borne nature of E. carotovora var. carotovora besides increasing vigour index of seedlings. Formalin at two per cent concentration also checked the growth of E. carotovora var. carotovora.

Keywords: Erwinia carotovora var. carotovora, onion, serodiagnosis, biocontrol, Pseudomonas fluorescens.