Mechanisms Of Chitosan Solution On The Inhibition Of Bacterial Leaf Blight And Leaf Streak Of Rice And Antibacterial Activity Of Chitosan-nanocomposites

Bacterial leaf blight and leaf streak are the two most damaging bacterial diseases of rice. However, few bactericidal chemicals are available for controlling both diseases. The antibacterial properties of two kinds of chitosan with different degree of N-deacetylation and molecular weight and their effect in protection of rice from bacterial leaf blight and leaf streak were evaluated. Our results showed that both chitosan solutions possess a strong antibacterial activity against both rice bacterial pathogens and significantly reduced disease incidence and severity compared to the control under greenhouse, and that the interaction between chitosan and rice pathogens were affected by chitosan type, incubation time, and chitosan concentration as well as bacterial species. The direct antibacterial activity of chitosan may be attributed to both membrane lysis and cell membrane integrity, and the destruction of biofilm evidenced by the evaluation of biofilm formation. In addition, both chitosan solutions significantly increased the activities of phenylalanine ammonia lyase, peroxidase and polyphenol oxidase in rice seedling following inoculation of two rice pathogens compared to the control. The role of chitosan in protection of rice against bacterial pathogens has been shown to involve direct antibacterial activity and indirect induced resistance.Our study indicated the chitosan/TiO2nanocomposites we synthesized show significantly higher antibacterial activity against rice pathogen compared to both alone in the light. In addition, the sensitivity of chitosan and chitosan/TiO2was significantly enhanced when the EPS was extracted. Our result of FTIR spectra indicated chitosan/TiO2nanocomposites can significantly reduced the concentration of protein of EPS which may be one important antibacterial mechanisms.