Study On Effects Of Azadirachtin On Learning And Memory Behavior And Ecological Adaptability Of Spodoptera Litura

In this paper,azadirachtin was selected as the stimulation condition to simulate the field application system.The habitual learning,associative learning and aversion learning and memory training of Spodoptera litura were carried out through the olfactory and taste senses.The effects of azadirachtin on learning,memory and ecological adaptability of S.litura were investigated.The antifeeding mechanism of azadirachtin was explained from the perspective of chemical receptors,and the brain tissues of S.litura were obtained by anatomical analysis under different insect ages and induced ways.The structure of brain and the expression of CREB protein in Lepidoptera were analyzed by immunohistochemical technique,which provided theoretical support for the study of creb memory protein in Lepidoptera larvae.In this paper,the following parts had been studied:Dealing with different concentrations of azadirachtin in the head of the third instar by microdrop method,such as taper receptor and so on,so as to determine the main action receptor of azadirachtin and determine the effect.The chemical receptors on the head of the third instar S.litura were treated with azadirachtin by microdrop method.The third instar S.litura showed obvious antifeeding effect.The higher concentration,the better antifeeding activity.Screening out vegetables that the S.litura like and don't like,and their taste sense and smell sense were used to train their chemical receptors after conditioned stimulation with azadirachtin,and then they were trained in learning and memory behaviors of preference and aversion.The behavioral changes were observed and the role of conditioned azadirachtin was determined.After conditioned stimulation of larval vision and taste by azadirachtin,aversion learning and memory training was carried out to observe the changes of their behavior,and the role of azadirachtin as a stimulus condition was confirmed.The third instar S.litura have different degrees of preference to different plants.The third instar S.litura developed the associated learning and memory behavior through the combined training of taste and olfactory.It is mainly habit learning and memory behavior,habitual learning and memory behavior and abhorrent learning and memory behavior.The S.litura larva,which has experienced the training of the smell source of kale leaf,showed a habit of learning and memory behavior in the later stage,and its first selection rate and response rate to the smell source of kale were higher than those of the control.The S.litura larva,which experienced the odor source of sweet potato leaves,showed habitual learning and memory behavior in the later stage,and its first selection rate and response rate to sweet potato leaf odor source were both higher than those of the control.The S.litura,which experienced a single odor source(including azadirachtin),showed aversion learning and memory behavior in the later stage,and the first selection rate and response rate to the smell source of kale were lower than those of the control.The third instar S.litura had different feeding patterns on cassava leaves and cassava leaves containing azadirachtin.With the increase of training time,the third instar of S.litura showed a habit of learning and memory to red light and yellow light,and the showed aversion to yellow light under the stimulation of azadirachtin.The choice of yellow light is less changeable,with the increase of training time,the aversion phenomenon is more obvious.The distribution of CREB memory protein in the brain of S.litura and the distribution under azadirachtin treatment were studied by Laser Confocal Technique to explore the relationship between azadirachtin and learning and memory of insects.In this study,the distribution and expression of CREB protein in the brain of S.litura were determined by immunohistochemical method for the first time.After treated with 1 mg/kg azadirachtin,the area ratio of CREB protein expression in the brain of the second instar of S.litura increased from 3.71% to 17.63%,and that of the fifth instar of S.litura increased from 3.29% to 28.55%.Comparing the spatial and temporal dynamic distribution of azadirachtin(irrigation root method and spraying method)on the seedlings of Brassica oleracea,and to determine the distribution dynamics of the S.litura under spraying and root irrigation.The degradation of azadirachtin on kale and soil accords with the first-order kinetic equation cn0e-kt.The half-life of azadirachtin on kale and soil was 0.26-0.88 d and 1.01 d,respectively,and the coefficient of variation was 0.84-0.97.The half-life of azadirachtin on kale and soil was 0.41-0.97 d and 0.80 d,respectively,and the coefficient of variation was 0.83-0.98.The azadirachtin was treated by irrigation and spraying.The distribution of S.litura on kale plants was as follows: the phenomenon of gathering and feeding on the leaf edge.Under the two treatments,the control effect of spraying method on S.litura was fast and the number of dropped insect was high.But under the method of irrigating root,the effect of spraying on S.litura is fast and the number of dropped insect was high.The control effect of this method was slow and the number of insect population decrease is less.