Quantitative Changes of Plant Defense Enzymes in Biocontrol of Pepper (Capsicium annuum L.) Late Blight by Antagonistic Bacillus subtilis HJ927

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 $53\%$ in pepper roots when preinoculated with B. subtilis HJ927 against P. capsici. The activities of PR proteins (chitinase and ${\beta}$-1,3,-glucanase) and defense-related enzymes (peroxidase, polyphenoloxidase, and phenylalanine ammonia lyase) decreased in roots of B. subtilis+P capsid-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.