Surface contact of cucumber or rice leaves with water can suppress their fungal diseases

Small amounts of water placed onto leaf surface for one day just before challenge inoculation were found to reduce severity of blast disease of rice and cucurbit scab of cucumber. The effect was only local in the first pathosystem and both local and systemic in the second one. In rice, the reduction in symptoms was preceded by increased superoxide production in the treated leaves. Presumably, water liberates plant elicitors inducing oxidative burst and other defense responses that render the plant relatively resistant. This reaction may be an adaptation of plants to higher risk of infections under humid conditions.

► Leaf pre-inoculation exposure to water droplets reduced severity of some diseases. ► The effect was systemic for cucurbit scab of cucumber and local for rice blast. ► In rice, the reduction in symptoms was preceded by increased superoxide formation. ► Presumably, water liberates plant elicitors inducing defense responses. ► This reaction may attenuate higher risk of infections under humid conditions.