The Relationship Between Cotton Hair Characteristics And Aphid Resistance And Its Physiological Mechanism Of Aphid Resistance

Cotton aphid is an important pest that harms cotton production.Breeding cotton varieties with hairy characteristics is considered to be one of the main ways or methods to resist cotton pests.However,the relationship between hair characteristics and cotton aphid resistance has not been conclusive,and there are few studies on the dynamic changes of hair characteristics.To this end,this study used five cottons with different hair differences as materials,and further analyzed the response changes of hair characteristics such as hair length and density,leaf composition thickness and other traits and their relationship with cotton aphid resistance at different growth stages.The relationship between leaf hair characteristics and aphid resistance was clarified;the physiological mechanism of aphid resistance of cotton hairy materials was revealed through the determination and analysis of the main antioxidant enzyme activities,soluble sugar content and volatile metabolites of different hairy materials.The research results have an important guiding role in screening aphid-resistant cotton materials and breeding new cotton aphid-resistant varieties based on the characteristics of fuzz in production.The main results of this study are as follows:1.The analysis of the hair characteristics of the 5 tested materials at different growth stages found that the cotton hair density changed differently in different periods.The hair density of KS2611 was bud stage >boll stage > seedling stage,while 20Y01,20Y03,HP565 and SWS-1.The growth changes of the hair density are the same,which is the seedling stage > bud stage > boll stage.From the same growth stage of each material,the hair density in the bud stage is HP565 > SWS-1,and the hair density in other stages is SWS-1 > HP565 > 20Y03 > 20Y01 > KS2611;the change trend of the hair length in different periods is the same,which is shown as seedling stage < bud stage < boll stage,and the difference in hair length between materials in the same period is small.There was no significant difference in the structural thickness of the leaves of the five materials at the bud stage,and there was no significant difference between the thickness of the upper epidermal cells and the thickness of the spongy tissue.2.The identification test of resistance to aphid in the field showed that the aphid damage index of the more hairy material was lower than that of the less hairy material.The indoor aphid resistance test showed that the selection of cotton aphid was related to the characteristics of hairs,and more cotton aphids chose less hairy materials;the reproduction rate of cotton aphid on different cotton materials was significantly different,and the reproduction rate of cotton aphid on the multi-hairy materials HP565 and SWS-1 was small.,strong aphid resistance.On the less hairy materials 20Y01,20Y03 and KS2611,the reproduction rate is large,and the aphid resistance is weak.The identification results of field and indoor aphid resistance were consistent,and the results showed that the aphid resistance of the more hairy material was stronger than that of the less hairy material.3.The relationship between hair characteristics and aphid resistance is shown as negative correlation between hair density and insect resistance index aphid damage index in different growth stages.The greater the hair density,the smaller the aphid damage index.Hair length,upper and lower cell thickness,palisade tissue,spongy tissue thickness and aphid resistance were less correlated.4.The research on the physiological mechanism of aphid resistance shows that the content of soluble sugar in cotton is closely related to aphid resistance.In normal seedlings,the soluble content in leaves of multi-hairy materials SWS-1 and HP565 was significantly higher than that of less-hairy materials KS2611 and 20Y01.The soluble sugar content in leaves of all materials increased after cotton aphid gnawed.The activity of phenylalanine ammonia lyase(PAL),peroxidase(POD),and polyphenol oxidase(PPO)in leaves were determined,and the difference between peroxide(POD)and phenylalanine in different materials of normal seedlings was determined.There were significant differences in acid ammonia lyase(PAL),in which the more hairy material was significantly higher than the less hairy material,and the difference in polyphenol oxidase(PPO)was not significant.After cotton aphid damage,the activities of the three enzymes were all increased.Among them,peroxide(POD)and polyphenol oxidase(PPO)KS2611were significantly lower than SWS-1,while phenylalanine ammonia lyase(PAL)had fewer hairs.There is no difference between the material and the hairy material.5.Through extensive targeted metabolomics analysis of the multi-hairy material SWS-1(group s)and the less-hairy material KS2611(group w)after docking,it was found that the metabolic level in cotton leaves changed significantly under the feeding stress of cotton aphid.A total of 1190 metabolites were detected by metabolomics,of which alkaloids accounted for the largest proportion,accounting for 15%.Among them,the ratio multiples greater than 7 were qingliguangning,patellogenin,and nordihydrocapsaicin.Aphid is closely related,followed by flavonoids,accounting for 12%,and phenols 8%.After the leaves of the s group and the w group were eaten by the cotton aphid,the analysis of the volatile matter content of the leaves showed that the metabolites in the s group were significantly different from those in the w group,including 24 kinds of metabolites that were significantly up-regulated,and 16 that were significantly down-regulated.Among the up-regulated substances,the number of olefinic substances is the largest,and the ratio is the largest,which are caryophyllene,D-limonene,styrene,basilene,(Z)-2-dodecene,and 3,5-octadiene.Followed by aldehydes,alcohols.In summary,the hair density gradually decreased with the progress of the reproductive period,while the length gradually increased.The greater the hair density,the stronger the aphid resistance,and the hair length has nothing to do with aphid resistance.The high aphid resistance of the multi-hairy material is closely related to the content of soluble sugar and peroxidase(POD)activity,and is closely related to the content of chloramphenicol,patinarin and nordihydrocapsaicin in the metabolite alkaloids,and the content of volatile substances.Caryophyllene,D-limonene,styrene,basilene,(Z)-2-dodecene,3,5-octadiene and other olefinic substances are closely related.