Pharmacodynamic Acnalysis of Anti-chitosan in the Prevention and Treatment of Tomato Virus Diseases

Abstract

Viral diseases are primary diseases of tomatoes with an occurrence rate generally reaching above 30% and up to 90% in severe cases. Control of viral diseases is an enormous challenge in crop protection. Application of insecticide for preventing virus transmission through reduction of insect vectors is considered an useful means. The crop breeding technology and tissue culture are also employed to generate viral resistant cultivar or virus-free seedlings. However, these methods are often less effective in practice because of viral mutations. It has been reported that chitosan, as an efficient plant resistance-inducing elicitor, can inhibit the infection of pathogenic bacteria, induce the production of phytochemicals and stimulate plant self-resistance, and has been widely used in the prevention and treatment of viral diseases. In this study, by investigating the field disease index and monitoring the form and content of the virus in the diseased leaves and new leaves before each application, it was clarified that continuous spraying of 0.5% chitosan water solution for 3 times at an interval of 7 days has a significant control effect of preventing tomato virus disease. Negative staining electron microscope observation method visually showed the existence and changes of virus in leaves; RT-PCR method analyzed the virus types as tomato spotted wilt virus (TSWV), tomato chlorosis virus (ToCV), tobacco mosaic virus (TMV); The qRT-PCR method further clarified that the inhibition rates of 0.5% chitosan solution on tomato spotted wilt and tomato chlorosis virus were 75.31% and 67.18%, respectively. It is concluded from our tests that the plant defence elicitor chitosan (a.i. 0.5%) is able to inhibit virus replication in crop cells and prevent the aggravation of tomato plant virus disease symptoms. Therefore, the strategy for the management of tomato virus disease is to apply the inducer chitosan regularly to maintain a low virus titer and prevent the occurrence and spread of virus disease.