Antifungal Mechanism Of Chitosan /oligochitosan Against Potato Dry Rot Caused By Fusarium Oxysporum

As one of the four major food crops in the world,potato is of great significance to solve the global food problem.Potato dry rot caused by Fusarium oxysporum is one of the main diseases in the process of potato storage and transportation,which causes a lot of losses in potato industry every year.At present,the commonly used prevention and control method is the use of chemical pesticides,but because chemical pesticides are toxic and can cause environmental pollution,it is not conducive to sustainable development.Chitosan is a kind of natural macromolecular polysaccharide with broad-spectrum antibacterial effect,which is widely used in many fields.Oligochitosan is the degradation oligomer of chitosan.In addition to the advantages of chitosan,oligochitosan has better water solubility.So as to explore the potential of chitosan/oligochitosan in the control of potato dry rot.This study explored the the direct effect of chitosan/oligochitosan on F.oxysporum,and the dry rot resistance of potato induced by chitosan/oligochitosan was also studied.The main results are as follows:（1）In vitro,chitosan could inhibit the mycelial growth and spore germination of F.oxysporum,resulting in twisted and entangled hyphae,terminal branching and cell shrinkage.Chitosan could increase the sensitivity of F.oxysporum to Na Cl/H₂O₂stress Combined with chemical pesticides,chitosan could inhibit the growth of F.oxysporum.It was found that the pathogenicity of F.oxysporum treated with chitosan/oligochitosan was weakened.By analyzing the transcriptome data of F.oxysporum treated with chitosan,the results showed that chitosan inhibited F.oxysporum by affecting the protein degradation,the expression of resistance related genes,Plant cell wall degrading enzymes（PCWDEs）and the expression of cell structure related genes.（2）Oligochitosan inhibited the mycelial growth of F.oxysporum in vitro.It was found that oligochitosan could significantly reduce the spore germination rate of F.oxysporum.The results showed that oligochitosan could lead the hyphae of F.oxysporum to entangle and twist into ropes,and the terminal branches of hyphae were much more than that of the control.Stress experiments showed that oligochitosan could further inhibit the growth of F.oxysporum under high temperature/low temperature/UV while Na Cl weaked the inhibition of oligochitosan to a certain extent.The pathogenicity of F.oxysporum treated with oligochitosan was weakened after inoculating several potato blocks.（3）Both chitosan and oligochitosan could induce the resistance of potato to F.oxysporum,and the activities of POD,PPO and PAL were changed in varying degrees in the induced potato compared with the control potato.