The Cotton Defense Response Induced By Acyrthosiphom Gossypii And Its Effect On Late Feeding Of Aphis Gossypii

Acyrthosiphom gossypii and Aphis gossypii are common pests in cotton fields in Xinjiang.For a long time,the competitive relationship between the two in cotton fields has changed with changes in external effects such as climate change,cultivation patterns,and pesticide application.In order to clarify the cotton defense response induced by Acy.gossypii,the temporal and spatial changes of Acy.gossypii populations on cotton,the effects of Acy.gossypii feeding on cotton physiological metabolism,key enzyme activities of the defense system,cotton transcriptome,and effects on late A.gossypii.The findings are as follows:(1)The population development and spatial distribution of Acy.gossypii on cotton are related to its initial infestation density.Under different initial density conditions,the population of Acy.gossypii on cotton showed a trend of first increase and then decrease,and all reached the peak after 4-5 days after receiving aphids.When the initial density was 15 heads per plant,the populations on the 4th and 10 th days were 72 heads per plant and 12 heads per plant respectively.The proportions of Acy.gossypii on the stalks in the initial and peak stages of population development were 35%-50% and 50%-80%,respectively.It can be seen that Acy.gossypii mainly harms cotton stalks and lasts for a short time.(2)The feeding of Acy.gossypii can change the related substances of nutrient metabolism and cell osmotic pressure regulation in cotton,and the synthesis and metabolism of important compounds in the secondary metabolic pathway.The chlorophyll content in cotton leaves was not significantly related to the feeding of Acy.Gossypii,and the contents of soluble sugar,soluble protein,carotenoids,MDA,and flavonoids all showed different growth rates with the increase in the density of the cotton aphid,and the feeding time.(3)After 1 day of feeding Acy.gossypii,the activities of CAT,SOD,POD in cotton leaves fed by 15 heads per plant of Acy.gossypii and the PPO and PAL activities of cotton fed with 3 densities significant increase in cotton than those in the control group.In addition,the activities of CAT,SOD,POD,PPO and PAL in cotton leaves showed different increasing trends with the prolonged feeding time of Acy.Gossypii.It can be seen that during the feeding process,Acy.gossypii will break the dynamic balance of the ROS system,activate the defense system of cotton,and promote the change of enzyme activity that has the function of scavenging and degrading toxic free radicals.(4)Acy.gossypii feeding caused differential expression of 6565 genes in cotton.KEGG enrichment analysis of these differential genes showed that a total of1224 differential genes were annotated,enriched in metabolic pathways,porphyrin and chlorophyll metabolism,biosynthesis of secondary metabolites,carotenoid biosynthesis,pentose phosphate.The annotated differential genes of metabolic pathways and biosynthetic pathways of secondary metabolites accounted for 92% of the total annotated differential genes.It can be seen that the feeding of Acy.gossypii has a great influence on the regulation of cotton physiological metabolism.(5)Feeding cotton fed by Acy.gossypii with different density,the development time of A.gossypii is prolonged,the life span of female aphid is shortened and the yield of aphid is decreased.Medium and high density of Acy.gossypii feeding on cotton can reduce the survival rate of A.gossypii.It can be seen that the growth rate of A.gossypii population on cotton after feeding by Acy.gossypii slowed down,and the maximum number of populations decreased.In summary,it can be known that the early damage of Acy.gossypii will cause gene expression differences in different metabolic pathways of cotton.The test results also showed that some key regulatory substances,secondary metabolites,and key enzyme activities in the defense system changed in varying degrees in the biological process of cotton after feeding on Acy.gossypii.And negative effects on the growth and development and population growth of A.gossypii in the later period.The plant defense response induced by feeding of Acy.gossypii is explained,which can provide a theoretical basis for the study of competition among pests occurring in different time and space of the same host plant.