Biological control of foot rot of black pepper with antagonstic bacteria from rhizosphere

Abstract

An attempt was made at the Department of Plant Pathology, College of Agriculture, Vellayani to screen and identify antagonistic soil bacteria with potentiality to suppress Phytophthora capsici, the incitant of foot rot or quick wilt of black pepper. Bacteria were isolated from the rhizosphere of wild pepper plants, pepper plants in disease free plantations, healthy plants in diseased pepper plantations, pepper plantations where organic farming is practiced, undisturbed forest soils and vermicompost. Population of bacteria in the various 50ils and vermicompost showed great variability ranging from 13.67xl04 to 168xl04 cfu g-1. High population of bacteria was recorded from the rhizosphere soils of healthy plants in diseased pepper plantation of Pepper Research Station, Panniyur and wild pepper plants in virgin forest of Punnamala region of Silent Valley. Of the 194 isolates, only 15 isolates showed antagonism to P. capsici in vitro. Three isolates B5, B7 and Bl3 were highly effective in in vitro inhibition of sporangial production by the pathogen and disease suppression in rooted cuttings of the susceptible pepper variety, Karimunda. Isolate B13 was found to be the most ideal candidate with the ability to reduce mortality of pepper plants and foliar blighting and to provide continued

protection for a longer period. The isolate was effective as cell free filtrates also and was found to produce small quantities of the enzyme, cellulase. Isolate B5 also reduced the disease in pepper plants. The live cells and cell free filtrate of this isolate afforded good foliar protection against P. capsici. The isolate B7 was found to have a dual role disease suppression and growth promotion. All these isolate~ had good survival in the rhizosphere of pepper plants with population of 104 to 105 cfu g-l soil. The effective isolates were gram positive, aerobic, sporulating, rods with ability to produce catalase and were found to conform to genus Bacillus.