|Park, Ro dong|
Submitted to: Journal of Microbiology and Biotechnology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/7/2005
Publication Date: 10/1/2005
Citation: Lee, H., Park, K., Shim, J., Park, R., Kim, Y., Cho, J., Hwangbo, H., Kim, Y., Cha, G., Krishnan, H.B., Kim, K. 2005. Quantitative Changes of Plant Defense Enzymes in Biocontrol of Pepper (Capsicium annuum L.) Late Blight by Antagonistic Bacillus subtilis HJ927. Journal of Microbiology and Biotechnology. 15:1073-1079. Interpretive Summary: The late blight disease causes serious damage to important crops world-wide resulting in significant loss of revenue. To date, synthetic chemical fungicides have been the most efficacious method used to control this disease. Use of fungicides has been associated with deterioration of soil physico-chemical properties, accumulation of toxic compounds, and an increase in pathogen resistance. Longevity and slow degradation rate of chemicals creates potential environmental and human health concerns. These concerns have forced researchers to find innocuous yet efficacious methods of disease control. Several soil microbes, which produce an array of biologically active compounds, can serve as potential biological control agents. In this study, we have demonstrated Bacillus subtilis HJ927 can significantly protect pepper plants from late blight caused by Phytophthora capsici. Information obtained from this study demonstrates that chitinase-producing soil bacteria could be utilized as potential biocontrol agents of important diseases. This practice should reduce the use of undesirable synthetic chemicals and promote maximum yield of important vegetable crops.
Technical Abstract: To investigate plant protection, pathogenesis related (PR) proteins and plant defense enzymes related to cell wall lignification were studied in pepper plants inoculated with antagonistic Bacillus subtilis HJ927 and pathogenic strain Phytophthora capsici. Phytophthora blight disease was reduced by 53 percent in pepper roots when preinoculated with B. subtilis HJ927 against P. capsici. The activities of PR proteins (chitinase and Ya-1,3-glucanase) and defense-related enzymes (peroxidase, polyphenoloxidase, and phenylalanine ammonia lyase) decreased in roots of B. subtilis+P. capsici-treated plants, but increased in leaves with time. The decrease and increase were much greater in P. capsici-treated plants than in B. subtilis HJ927+P. capsici-treated plants, although P. capsici treated plants had more severe damage. Therefore, changes of enzyme activities do not seem to be directly related to plant protection. We suggest that the change of these enzymes in pathogen-treated plants may be related to plant response rather than to resistance against pathogen attacks.