Preparation And Nematicidal Activity Evaluation Of(Phosphorus, Sulfur And Fluorine-) Containing Chitosan Oligosaccharide Derivatives

China is rich in marine resources.It is a hot topic to extract the active functional components from it for application in several fields.Chitosan or chitosan oligaosaccharide?COS?which is extracted and producted from the shrimp or scrap shells is a biocompatible,biodegradable,modifiable natural macromolecule.Because of its inhibitary ability against microorganism and plant growth promoting effect,it has great potential applications in agriculture.It has been an important source for the development of new pesticides.The root knot nematode disease in the process of agricultural production causes great losses of yield and economic annually,and it is not easy to be preventted and controlled.Currently,there are few kinds of nematicides which are very harmful to the environment and human by high toxicity.It's urgent to develop novel,green,highly effective and low toxic nematicides.In this paper,three kinds of derivatives contain phosphorus,sulfur and fluorine with nematicidal activity were prepared firstly by grafting phosphate esters,dithiocarbamates and trifluorobutene groups onto chitosan/chitosan oligosaccharide backbone respectively,and their structures were characterized.Then,the nematicidal activity against Meloidigyne incognita?M.incognita?and plant immune regulation effect of derivatives were evaluated.The main results are as follows:1.The phosphoryl ester functional groups can improve the water solubility,nematicidal activity of chitosan/COS:chitosan/chitosan oligosaccharide Schiff base-poly ethylamine-diethyl phosphonyl ester derivatives had well water solubility,plant inducing activity and low plant toxicity;The nematicidal activity and inhibitory activity of egg hatching of COS derivatives were higher than chitosan derivatives;In phosphorus containing derivatives,chitosan salicylaldehyde Schiff base-poly ethylamine-phosphate diethyl ester and chitosan oligosaccharide salicylaldehyde Schiff base-poly ethylamine-phosphate diethyl ester derivative had the highest nematicidal activity against M.incognita,and their LC₅₀/72h?0.39mg/m L and0.27mg/mL?were lower than 3.93mg/m L of COS respectively,meaning the nematicidal activities were obvious higher than COS.2.The dithiocarbamates functional groups can improve nematicidal activity and egg hatching inhibitory activity of COS:COS derivatives were more conducive to obtain water solubility than chitosan derivatives;All COS-dithiocarbamates derivatives had well water solubility,plant inducing activity and low plant toxicity;In sulfur containing derivatives,chitosan oligosaccharide-dithiocyclobutane derivative had highest nematicidal activity against M.incognita with LC₅₀/72h=1.23mg/m L and egg hatching inhibition activity with IR/14d>90%,its nematicidal activitie was obvious higher than COS.3.The trifluorobutene groups and thiadiazole groups can enhance the nematicidal activity,inhibitory activity of egg hatching and plant inducing activity of COS:All fluoride derivatives and intermediates,had well water solubility,nematicidal activity,plant inducing activity and low plant toxicity;chitosan oligosaccharide–thiouresa,chitosan oligosaccharide thiadiazole,chitosan oligosaccharide–thiadiazolen–trifluorobutene derivatives had strongest nematicidal activity against M.incognita,and their LC₅₀/72 were about 0.063mg/mL which showed the obvious higher nematicidal activity than COS.4.The inhititory activity against Meloidigyne incognita J2s and egg of chitosan and COS can be improved by structure modification,at the same times,the derivatives had plant growth regulating ability and the inducing activity of pathogenesis-related protein such as chitinase,?-1,3-glucanase,peroxidase,phenylalanine aminotransferase,polyphenonl oxidase.In this paper,for the first time,a series of phosphorous,sulfur and fluorine functional groups with nematicidal activity were grafted on the polysaccharide backbones to obtain chitosan/chitosan oligosaccharide derivatives.The derivatives not only can play the biological activity of chitosan/chitosan oligosaccharide molecule itself,such as plant growth regulation and inducible resistance,but also have nematicidal ability with low toxicity.Therefore,they have great potential for application.This study suggested that new nematicides can be developed from the structure modification of bioactive molecular such as chitosan and COS.In a word,it provides a new way for the development of green,efficient and low-toxicity nematicides.