Abstract: 0.5 mmol/L BTH was used in seedlingwith two true leaves 4, 8 and 12 h, or 1, 2, 4 and 7 days before or 4 and 2 days after inoculation with P.cubensis. Results obtained showed that BTH had not a curative effect but could induce local and systemic resistance in cucumber against the downymildew. Expression of systemic resistance in leaves was detectable 48 h after treatment and continued for at least 7 days. Chitinase and β-1,3-glucanase activities analysis showed that induced resistance in cucumber leaves was
accompanied by a systemic increasing in both enzymes activities. Two enzymes were related to resistance to downy mildew in cucumber.

Key words: Cucumber downy mildew, BTH, Induced resistance, Chitinase, β-1, 3-glucanase