| A bioassay for induced systemic resistance (ISR) to Botrytis cinerea in bean has been used to evaluate ISR by a root treatment with Trichoderma harzianum T39 (Trichodex). Previously, it was reported that the salicylic acid-producing rhizobacterium Pseudomonas aeruginosa KMPCH induced resistance in the bean-Botrytis bioassay. Bean plants grown in a soil treated with T. harzianum T39 showed significantly less disease symptoms upon Botrytis cinerea inoculation to the leaves compared with untreated control plants. The observed disease reduction with T. harzianum T 39 was of the same level as in P. aeruginosa KMPCH-treated plants. In order to evaluate the spectrum of this ISR, another fungal pathogen, Colletotrichum lindemuthianum, was used. A 105 ml-1 inoculum was sprayed on primary leaves of 10-day-old beans. Development of anthracnose symptoms was reduced on plants grown in a soil treated with either T. harzianum T39 or P. aeruginosa KMPCH compared with the control. When a 106 spores/ml inoculum was used, P. aeruginosa KMPCH treatment no longer reduced anthracnose symptoms but ISR by T. harzianum T39 was still observed. These results indicate that at least in the bean-Colletotrichum system, the ISR by P. aeruginosa KMPCH and T. harzianum T39 seemed to be different. Mechanisms involved remain to be studied. |
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