Inoculation Method of Pectobacterium carotovorum sub-sp. carotovorum and Factors Influencing Development of Bacterial Soft Rot in Radish

摘要

Among the five inoculation methods evaluated for induction of bacterial soft rot (Pectobacterium carotovonim sub-sp. carotovorum) on radish, stabbing of roots and cut surface method with the pathogen suspension (108 cfu/ml obtained from 18 h old growth) induced the highest level of rotting (5 cm~2). However, cut surface inoculation method was convenient and effective for field studies. Investigations on the influence of the levels of inoculum, temperature and relative humidity on bacterial soft rot development in radish were carried out under controlled conditions by per cent weight loss assay. Complete rotting of radish was recorded at 48 h after inoculation with a bacterial load of 10~(12) cfu/ml. However, it took 72 h for complete rotting when 10~8 cfu/ml was used. The pathogen at less than 10~5 cfu/ml failed to induce rotting. Increased temperature (20 to 35C) enhanced the rotting ability of the pathogen. Similarly at increased RH levels, rotting was increased. The highest rotting levels were recorded when radish discs were incubated at 35C and 100% RH.