On The Effects Of Pathogen-inhibition And Systemic Inducing Resistance Of Two Oligosaccharides

Zhongke -2 Zhongke -6, two kinds of active substances ?oligosaccharides, which were extracted from the cell wall of some fungi. Oligosaccharides can stimulate responses of the immunity reaction of plant, in this couse, there are some resistance substances come into being so as to inhibite the incidence of disease.In this study, we take TEV on tabacco, WMMV on vegetable marrow, anthracnose on cucumber, powdery mildew on cucumber as objects, research on the resistance mechanism of oligosaccharides, through analyzing the inhibition to some pathogens, effect and the reaction of histology and Ultrastructure.The research results are following:(1) The inhibition of two oligogalacturonide and oligochitosan, to the mycelial growth was studied by injecting the culture medium at different concentration in Fusarium oxysporitm f.sp.cucumerirum, Gibberella zeae, Glomerella cingulata and Exserohilum turcicum.The effect of oligosaccharides on spore germination were evaluated in Pseudoperonospora cubensis and Puccinia striiformis WestThe results indicated that oligosaccharides had inhibition on phytopathogens ,and the degree of inhibition depend on the concentration of oligosaccharides.(2) The protection of oligosaccharides for the disease of TMV and WMMV was tested in greenhouse.The result sindicated that the two oligisaccharides can decrease the severity of diseases, release symptom of leaves ,and abnormal occurred lessly .After treatment with oligosaccharides in 5-7 days ,the resistance expression of inoculated plant up to the maximum .(3)The efficacy of medicament on anthracnose > powdery mildew have been measured.After treatment with oligosaccharides in cucumber,the severity and infection type of diseases is lower than control .The thick of colony on the disease leaves is thin ,spore production decreased obviously . After treatment with oligosaccharides.there are no differences between treatments and checks on latent period.The time of spore production was prolonged obviously,which treatment time is 5-7 days before inoculation. Compared to control,the time of spore production prolonged 5 days in the inoculation of 7th days after treatment, the production of spore reduced as well.(4)The histology of oligosaccharides on the development of powdery mildew was examinated with light microsocopy.The geminating rate of spore and apprssorium formatting rate was higher than control at beginning and reach the same level 48h later.Under the invasion site where papilla can be form,the haustoria formation rate was lower .colony extension was inhibited.The number of spore strain of one cology and spore of one strain reduced too.(5)The expression of Ultrastructure reflected in two aspects,one is the pathogens.the other is host. The main changes is depression, cell necrosis, the details expression in cell is depression of subdivisions of colony and haustoria, accumulation of cell matrix, cellular organ dissociation and cellular tissue collapse; the original reaction performance in disease that pathogen invasion is to make the cell wall thicken ?some black material deposite between cell wall and membrane.In conclusion .oligosaccharides have the effect of inhibition ,and the resistance can be induced ,the severity of diseases decreased , histology and Ultrastructure had some changes correlation with resistance ,but all that had happened can be realized under the condition of high concentration.