Isolation of Antagonistic Microbes for Biological Control of Ginseng Root Rot

Ginseng (Panax ginseng C.A. Meyer) is widely cultivated in Korea as a medicinal herb. Ginseng yield have recently been reduced by various factors, e.g. abnormal climate, disease and insect damage. Cylindrocarpon destructans, Fusarium solani and Sclerotinia sclerotiorum are major pathogens causing root rot disease in ginseng. Yield losses of ginseng reached up to 30 – 60% due to various diseases caused by C. destructans, F. solani and S. sclerotiorum during ginseng cultivation. It is well known that biological control using microorganism is eco-friendly method which can prevent disease in ginseng cultivation. Antagonistic microorganism can replace chemical agent, and reduce yield losses caused by several pathogens. In addition, antagonistic microorganism is also known to improve yield of ginseng by promoting the activity of plant root. For isolation of antagonistic microorganisms suppressing growth of pathogen, soil samples were collected from ginseng cultivation area and antimicrobial activities of isolates from soil were evaluated. Two strains that have antifungal activity against C. destructans, F. solani and S. sclerotiorum were isolated from soil. The optimum temperature ranges for growth of isolates were 25˜30 °C and both strains had protease activity. Analysis of the 16 s rDNA gene sequence revealed that these isolates belongs to genus Bacillus. 16 s rDNA gene sequence of each strain showed 99˜100% of sequence similarity with B. subtillus and B. amyloliquefaciens, respectively. Ginseng root rot caused by pathogens was decreased 27.3%˜ 56.7% by B. subtillus while decreased 18.9% ˜ 67.5% by B. amyloliquefaciens (Table). These results suggested that these microbes could be used as biological control agent for prevention of major pathogens in ginseng cultivation.

Tab. 1: Rot symptom degree of ginseng root.

Isolate	CDa)	FS	SS
N.T.b)	3.0c)± 00	4.0 ± 0.0	3.7 ± 0.5
B. subtillus	1.3 ± 0.5	1.7 ± 0.5	3.0 ± 0.0
B. amyloliquefaciens	1.7 ± 0.5	1.3 ± 0.5	2.7 ± 0.5
a) CD: C. destructans. FS: F. solani, SS: S. sclerotiorum b) NT: not treated. c) Rot symptom degree: 0 (not rotted), 1 (yellow color), 2 (light brown color). 3 (deep brown color), 4 (severe rotted)