Bacillus spp. as biocontrol agents of root rot and phytophthora blight on ginseng

Abstract

Ginseng (Panax ginseng) is one of the most widely cultivated medicinal herbs in Korea. However, yield l osses reached up to 30-60% due to various diseases during 3 or 5 years of ginseng cultivation in the country. Therefore, successful production of ginseng roots depends primarily on the control of diseases. The objective of this study was to select potential biocontrol agents from rhizobacteria isolated from various plant internal root tissues for the control of multiple ginseng diseases as an alternative to fungicides. Among 106 Bacillus strains, two promising biocontrol agents, Bacillus pumilus strain B1141 and Paenibacillus lentimobus strain B1146, were selected by screening against root rot of ginseng caused by Cylindrocarpon destructans in a greenhouse. Pre-inoculation of selected isolates to seed or 1-year-old root of ginseng resulted in stimulation of shoot and/or root growth of seedlings, and successfully controlled root rot caused by C. destructans (P<0.05). Furthermore, drenching of cell suspension of the selected isolates on seedling-growing pots reduced the incidence of Phytophthora blight after the seedlings were challenged with zoospores of Phytophthora cactorum (PcO.OS). P. lendmorbus strain B1146 showed antifungal activity against various soil-borne pathogens in vitro, while B. pumilus strain B1141 did not show any. Results of this study suggest that some rhizobacteria can induce resistance against various plant diseases on ginseng.