Tobacco's Defense Response And It's Mechanism Induced By Chitosan

1.The antifungal activities of chitosan with different concentrations on 8 pathogens were investigated in vitro.It was found that the chitosan had a direct effect on the morphology,growth and multiplication of the chitosan-treated pathogens.When concentration was≥0.2%,growth of 7 pathogens showed significant difference(P＜0.05)compared with the control except for Colletotrichum gloeospotioides.The antifungal activities increased as the chitosan concentrations gradually varied from 0.75g/L to 5.0g/L.The higher concentration was,from 0.75g/L to 5.0g/L,the more remarkable effect of antifungal activity was;but there wasn't a linear correlation between them;the growth of Colletotrichum gloeospotioides was accelerated at concentrations of 0.75g/L.The antifungal effect of chitosan would keep longer with higher concentrations.In addition,the minimum inhibitory concentration(MIC) of the 8 fungi were tested,ranging from 3.0g/L to 5.0 g/L depending on the fungi species.In the present study,the antifungal activity of chitosan was influenced by concentrations,time and the fungi species.2.The antifungal activity of chitosan with different molecule weights (MWs),concentrations and pH against Phytophthora parasitica var nicotianae(Ppn)were investigated in the study.As a result,the aberrance of mycelium was found,and the metabolism and cell wall were destroyed too.At the lower concentration(≤0.625mg/L),the antifungal effect increased with MWs' increasing;and chitosan with lower MW would be more easily affected by its concentration.At≥5.0mg/L,the chitosan sample with the MW of 4.7×10~4 had the strongest antifungal activity.Chitosan was affected greatly by pH except for the one of 5×10~3. Chitosan with various MWs had different antifungal mechanism.The chitosan of 5.0×10~3 basically penetrated the fungi to kill or inhibit their growth,on the other hand,chitosans of 2.01×10~5 and 9.0×10~5 would be on the surface of fungi to form a membrane which could interfere the metabolism of Ppn,and the 4.7×10~4 one probably had the two mechanisms.3.We studied the changes in peroxidase(POD)and phenylalanine ammonia-lyase(PAL)activities in susceptible and resistant tobacco after inoculated with Ppn and sprayed with chitosan solution,then analysed the POD isozymes by PAGE.POD and PAL activities showed a significant increase after treated with chitosans respectively.The time and intensity were different between them,and the resistant one had higher activity. One peak of POD was found in the tobacco after activated by Ppn too.To PAGE of peroxides isozylnes,significant changes were found in pigmentation of 4 POD zones,and the pigmentation of those which treated with chitosan was deeper than CK.No new zones of POD were found in the leaves of tobacco treated with chitosan or inoculated with Ppn.It indicated that the POD and PAL activity could be activated by chitosan,which related with the MWs,concentrations of chitosan.4.The effect of chitosan and Ppn on the change of proteins and compounds in the leaves of tobacco were studied by SDS electrophoresis and IR spectroscopy.The protein of Ppn was less than CK after treated with chitosan.Except for these,the peaks of IR spectroscopy were higher and wider indicating that more compounds were synthesized.It differed from the changes of SDS electrophoresis of protein in Ppn.To tobacco, wider and higher peaks and deeper pigmentation zones were found.And no new zones or peaks appeared or disappeared,the change of capacity of them was the primary response to treatment.So the increasing of antifungal activity to Ppn was a systemic response.5.The conductance in the leaves of tobacco was investigated after sprayed by the chitosan.The chitosan could reduce the conductance which indicated the increasing of ability of resistance to stress.The resistance to Ppn induced by chitosan greatly in the tobacco,and disease index became lower.The rate of relative resistance efficiencies respectively reached 29.9%and 44.1%in honghuadajinyuan and zhongyan 100 at 72h and 48h after treated with chitosan,and the relative resistance efficiencies of chitosan were influenced by their MWs, concentrations and how long it was between chitosan spraying and Ppn inoculation.Peroxides isozyme...