Inhibitory Mechanism Of Polysiloxane Grafted Quaternary Ammonium Salt Against Banana Fusarium Wilt

Banana fusarium wilt is a typical soil-borne disease caused by the fungus infestation of Fusarium oxysporum f.sp.cubense?Foc?,which is one of the important diseases that restrict the development of banana farming,and among them,the No.4physiological race?Foc4?is the most serious harm.In chemical control,although many chemicals showed obvious inhibition or even killing effect on Foc4 in laboratory testing,the easy loss of chemicals in field would reduce the controlling effect.The vast majority of approved fungicides for Foc4 are small molecular structures,and it is difficult to make the long-term adsorption in the complex soil environment,and also difficult to contact and kill the pathogen in the soil,while easy to irrigation and rainwater loss,for these chemicals with low molecular weights.Aiming at the above problems,in this dissertation,we designed and synthesized a kind of polymeric quaternary ammonium salt with amphiphilic,namely:polysiloxane grafted quaternary ammonium salt?PDMS-g-BC?,whose polymer backbone is hydrophobic polydimethylsiloxane?PDMS?containing hydrophilic and good bacteriostatic dimethylbenzyl quaternary ammonium salt side groups.The hydrophobic-hydrophilic structure of PDMS-g-BC has both the general properties of macromolecular surfactants and stable adsorption on solid?e.g.,soil particles?due to the“hydrophilic-hydrophobic interaction”,which makes it a long-term adsorption in the soil.Based on the polymer synthesis,this dissertation firstly compares the inhibition effect and inhibition mechanism of PDMS-g-BC against Foc4 with another hydrophilic macromolecule quaternary ammonium salt homopolymer?polyacrylamide quaternary ammonium salt,PQD-BC?and a commercial low molecular weight quaternary ammonium salt?benzalkonium chloride,BC?which has the similar quaternary ammonium salt groups with PDMS-g-BC and PQD-BC;and further studied the adsorption characteristics of above two polymeric quaternary ammonium salt and BC in soil and antifungal properties in soil.The results showed that the inhibitory activities of PDMS-g-BC and PQD-BC against Foc4 were similar to that of BC in the common plate and broth.The IC₅₀,IC₉₀,MIC and MFC for PDMS-g-BC were 0.64,7.05,0.15,0.4 mg/mL,respectively.It mainly caused the lipid peroxidation of the cell membrane by destroying the cell wall and cell membrane,affecting the normal function of mitochondria and genomic DNA,thus cause the death of the fungal cells.Further soil leaching and soil inhibition tests show that only amphiphilic macromolecule quaternary ammonium salts,i.e.,PDMS-g-BC,could be effectively adsorbed in the soil?for example,when the initial concentration of PDMS-g-BC in soil0.1%wt,there was still about 80%effective adsorption rate after leaching.?,and the adsorbed PDMS-g-BC in soil showed strong inhibitory effect on Foc4,while for the same conditions,PQD-BC and BC were easy to lose from the soil?the effective adsorption rate of only about 10%?and showed less inhibition against Foc4.The good adsorption properties of PDMS-g-BC in the soil gives it a good&potential application on the control of Foc4.