Effects Of Combined Application Of Nitrogen And Potassium On Aphid Resistance In Chrysanthemum

Macrosiphoniella sanborni Gilletteisone of the most harmful pests of chrysanthemum(Chrysanthemum morifolium),at present,the production is mainly chemical-based,not only increase production costs,but also increase pesticide residues in products.Nitrogen and potassium fertilizer is not only a necessary element of plant nutrition,but also a large number of chemical fertilizers produced in agriculture at present,excessive fertilization or improper fertilization will cause plants to suffer from greater pest pressure.The related research shows that the scientific application of nitrogen and potassium fertilizer will have a significant effect on the life parameters of herbivorous insects and control the growth and development of pests.Therefore,the study of nitrogen and potassium fertilizer application is of great theoretical and practical significance for improving the comprehensive control of chrysanthemum aphids.This test mainly takes chrysanthemum as the test material,under different concentrations of nitrogen and potassium application level treatment(N0K0,N1K1,N1K2,N1K3,N2K1,N2K2,N2K3,N3K1,N3K2,N3K3),the chrysanthemum seedlings during the inoculation of aphids.The population dynamics of aphids after inoculation were investigated,and the changes of nutrients,osmotic regulators,secondary metabolites and defensive enzyme activities of chrysanthemumafter aphids were compared.The main findings were as follows:1.Aphids investigation results showed that the breeding ratio of aphids of N0K0 was the highest and the N2K2 propagation ratio was the lowest,and the results showed that:CK>N3K3>N3K2>N1K3>N1K1>N1K2>N2K1>N3K1>N2K3>N2K2after the 10 plants were inoculated with aphids under the condition of nitrogen potassium application.It can be seen that the treatment under the condition of N2K2 level was more favorable to control the number of aphids,and the N2K2 can also alleviate the inhibition of plant growth which were caused by aphids.2.Reasonable nitrogen and potassium fertilizer application to a certain extent reduced the soluble sugar in chrysanthemum leaves and improved the content of soluble protein.After the plant was inoculated with aphids,the correlation analysis showed that the reproductive ratio of soluble sugar was positively correlated with that of aphids,and there was a certain negative correlation with soluble protein.It can be explained that under the condition of nitrogen and potassium application,the plant resistance to aphids was improved by reducing the endogenous soluble sugar and increasing the content of soluble protein in the plant underaphids infestation.3.Reasonable nitrogen and potassium fertilizer application can improve the content of secondary metabolites(flavonoids,total phenol,lignin)in the plant,among which CK secondary metabolites had the lowest content and the N2K2 had the highest,and the correlation analysis showed that the secondary substances in the plant were negatively correlated with the propagation ratio of aphids.It can be explained that the application of nitrogen and potassium can improve the aphid resistance of plants by increasing the content of secondary metabolites in the inner source of chrysanthemum.4.Reasonable nitrogen and potassium fertilizer application can affect the plant endogenous osmotic regulation substances and improved the content of proline to reduce the content of the membrane lipid peroxide product malondialdehyde,thus reducing the oxidation damage of the plant,improving the plant resistance to aphids,of which the content of MADof N2K2 was the lowest,proline content was the highest and the largest variation.5.Reasonable nitrogen and potassium fertilizer application can improve the activities of the endogenous SOD,POD,CAT,PAL,PPO and TAL,and increased the content of the secondary metabolites in the plant.Among them,the enzyme activitiesof N2K2 treatment was the highest,the change amplitude was the largest,and the correlation analysis showed that the content of secondary substances in plant leaves was negatively correlated with the propagation ratio of aphids,and nitrogen and potassium application could not only improve enzyme activity and increase the content of secondary substances,but alsocould enhance the resistance of chrysanthemum to aphids.