Mycobiology.  2002 Mar;30(1):31-36.

Selection and Efficacy of Soil Bacteria Inducing Systemic Resistance Against Colletotrichum orbiculare on Cucumber

• Kwack MS
• Park SG
• Jeun YC
• Kim KD

Abstract

Soil bacteria were screened for the ability to control cucumber anthracnose caused by Colletotrichum orbiculare through induced systemic resistance (ISR). Sixty-four bacterial strains having in vitro antifungal activity were used for selecting ISR-inducing strains in cucumber. Cucumber seeds (cv. Baeknokdadagi) were sown in potting mixtures incorporated with the soil bacteria, at a rate of ca. 10(8) cells per gram of the mixture. Two week-old plants were then transplanted into the steam-sterilized soil. Three leaf-stage plants were inoculated with a conidial suspension (5x10(5) conidia/ml) of C. orbiculare. Diseased leaf area (%) and number of lesions per cm2 leaf were evaluated on third leaves of the plants, 5~6 days after inoculation. Among 64 strains tested, nine strains, GC-B19, GC-B35, GK-B18, MM-B22, PK-B14, RC-B41, RC-B64, RC-B65, and RC-B77 significantly (P = 0.05) reduced anthracnose disease compared to the untreated control. In contrast, some bacterial strains promoted susceptibility of cucumber to the disease. From the repeated experiments using the nine bacterial strains, GC-B19, MM-B22, PK-B14, and RC-B65 significantly (P = 0.05) reduced both diseased leaf area (%) and number of lesions per cm2 leaf in at lease one experiment. These strains with control efficacy of 37~80% were determined to be effective ISR-inducing strains.

Keyword

Anthracnose; Colletotrichum orbiculare; Cucumber; Induced systemic resistance; Soil bacteria

MeSH Terms

Bacteria*
Colletotrichum*
Soil*
Soil