Chitosan was evaluated for its potential to induce antifungal hydrolases in susceptible turmeric plant (Curcuma longa L.). Under field conditions, the application of chitosan (crab shell) to turmeric plants by foliar spray method induces defense enzymes such as chitinases and chitosanases. Such an increase in enzyme activity was enhanced by spraying chitosan (0.1%？w/v) on leaves of turmeric plants at regular intervals. Gel electrophoresis revealed new chitinase and chitosanase isoforms in leaves of turmeric plants treated with chitosan. Treated turmeric plants showed increased resistance towards rhizome rot disease caused by Pythium aphanidermatum, whereas control plants expressed severe rhizome rot disease. Increased activity of defense enzymes in leaves of chitosan treated turmeric plants may play a role in restricting the development of disease symptoms. The eliciting properties of chitosan make chitosan a potential antifungal agent for the control of rhizome rot disease of turmeric. 1. Introduction The rhizome rot disease caused by Pythium aphanidermatum is the most destructive disease of turmeric plants in India, which reduces its economic and commercial value [1, 2]. At present, effective fungicides are not available. Therefore, it is necessary to search for effective methods to control this pathogen. The possibility of stimulating internal plant defenses has become an interesting option for enhancing natural disease resistance. Higher plants have the ability to initiate various defense mechanisms when they are infected either by phytopathogens or after treatment with biotic and abiotic elicitors. Among the elicitors known to date, chitosan, a polyvalent cation, has been shown to act as a potent oligosaccharide elicitor which can induce defense responses in plant tissue [3]. Plant defense-related enzymes were known to participate in early defense mechanisms and to prevent pathogen infections [4, 5]. Chitosan has attracted tremendous attention as a potentially important biological resource due to its biological properties including biocompatibility, nontoxicity, and biodegradability [6]. Chitosan has been found to interfere with the growth of several plant pathogenic fungi [4, 7–9]. The potential of chitosan to protect fungal diseases of various horticultural plants has been studied in various investigations [4, 9–11]. The interest in the antimicrobial properties of chitosan was focused on its possible role in plant protection. Hence, the present study was carried out to induce resistance in susceptible turmeric plant (Erode local) against rhizome
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