Role of Chitosan in Induction of Defense Response against Phomopsis Vexans and Augmentation of Growth and Yield of Eggplant
Phomopsis blight and fruit rot disease caused by the fungus Phomopsis vexans is one of the most devastating diseases of eggplant that causes great economic losses especially in tropical and subtropical climates. An experiment was conducted to evaluate the antifungal properties of chitosan against P. vexans by inducing defense-related enzymes and increase the growth and yield contributing characters of eggplant. P. vexans isolate VS-2 was identified as most virulent against eggplant by pathogenicity test. The concentrations of chitosan 0, 0.1, 0.2, 0.3, 0.4 and 0.5% were used to control the fungus in in-vitro trial. There was an effect on mycelial growth reduction of P. vexans by chitosan. The highest mycelial growth reduction was found with 0.5% chitosan at seven days after incubation. Consequently, seeds were treated with chitosan @ 0.5% concentration. Chitosan enhanced the germination percentage and seedling growth such as shoot length, root length, fresh weight and dry weight and reduced post-emergence seedling mortality. In the field condition, chitosan reduced leaf blight and fruit rot disease incidence and severity, simultaneously increased plant height and number of branching in eggplant after certain maturity. It was also found to increase the yield and yield contributing characters of eggplant. The defense enzymes catalase (CAT) and peroxidase (POD) activities were also increased several folds by this elicitor. Chitosan contains antifungal properties against P. vexans as well as growth promoting substances to induce resistance of eggplant.
