A cell wall glucan elicitor induces resistance in taro against Phytophthora leaf blight

A cell wall glucan elicitor preparation was isolated from the mycelial walls of Colocasia leaf blight pathogen, Phytophthora colocasiae. Response of different cultivars of Colocasia to elicitor treatment on detached leaves, injection in plants and spraying on the leaves were tested. Elicitor treatment on the detached leaves resulted in a quick initiation of hypersensitive reaction (HR) in resistant cultivars but it could not induce HR in susceptible cultivars. In susceptible cultivars, only slight yellowing without any necrotic spots was observed. The elicitor injection induced resistance to P. colocasiae even in the susceptible cultivars while elicitor spraying did not show any significant induction of resistance. Elicitor injection induced systemic resistance in both the susceptible and tolerant cultivars. However, the induction of resistance in susceptible cultivars was delayed compared to the tolerant cultivars. When the pathogen was inoculated on the resistant cultivars 5 days after elicitor injection, the leaf area damaged and number of spots per plant were less compared to the susceptible cultivars. The response of different cultivars to elicitor injection under pot culture conditions and field conditions has been discussed.