Effect Of Exogenous Calcium Seed Priming On Resistance To Schizaphis Graminum (Hemiptera: Aphididae) And Its Mechanism In Guizi 1 Wheat

Schizaphis graminum（Rondani）is one of the main insect pests affecting the production of Triticum aestivum L.Calcium,as an essential element in plants,is a key regulator of plant response to biotic and abiotic,and participates in kinds of signal transduction.In this study,wheat and Schizaphis graminum（Rondani）were treated with exogenous calcium at seed stage,The effects of the different concentration of exogenous calcium seed soaked of Schizaphis graminum（Rondani）development period,population size,feeding behavior were compared,and the content of Ca²⁺in wheat plant leaf,expression of key genes in calcium signal transduction pathway（calmodulin TaCaM,calcium dependent protein kinases TaCDPK and CBL interacting protein kinase TaCIPK）,callose content,callose deposition area,callose synthase（TaGSLs）gene expression differences.To explore the molecular mechanism of seed soaked treatment with exogenous calcium to induce wheat resistance to Schizaphis graminum（Rondani）,in order to use exogenous calcium to regulate wheat autoimmunity,explore green and ecological control of Schizaphis graminum（Rondani）the new method provides a theoretical basis.The main results are as follows:1 Effects of exogenous calcium soaked treatment on the growth,population size and feeding behavior of Schizaphis graminum（Rondani）The optimal concentration of CaCl₂ seed soaking treatment was selected by observing the developmental period of Schizaphis graminum（Rondani）.On this basis,the effects of the optimal concentration of CaCl₂ seed soaking treatment on the population and feeding behavior of Schizaphis graminum（Rondani）was further studied.The results show that:（1）Wheat seed soaking treatments with different concentrations of CaCl₂all prolonged the developmental period of the 1^st,2^nd,3^rd and 4^th instar of Schizaphis graminum（Rondani）,the aphid fed on 20 mM CaCl₂ soaked the wheat plants to its 1^st,2^nd,4^th instar and nymphal instar was the longest developmental period of Schizaphis graminum（Rondani）,was significantly longer than that of the wheat seedlings treated with water soaking by 0.53,0.35,0.25 and 1.24 d;（2）After 10 days of Schizaphis graminum（Rondani）feeding on 20 mM CaCl₂soaked the wheat plants,the population of wheat aphid was 29.02%less than that of wheat plants soaked with water;（3）Feeding behavior research results showed that,when Schizaphis graminum（Rondani）fed on wheat plants soaked with CaCl₂,the number of probing np wave,C wave,pd wave,E1 and E2 were significantly increased,the total duration of np wave,C wave,pd wave,F wave,average duration of F wavetotal E1 wave were prolonged,the total probing time,average duration of pd waves,total duration of E2 waves and average duration of E2 waves are shortened.The results showed that seed soaked with 20 mM CaCl₂ could significantly prolong the growth and development time of Schizaphis graminum（Rondani）,reduce the population of Schizaphis graminum（Rondani）,and Change the feeding behavior of Schizaphis graminum（Rondani）.2 Effects of exogenous calcium soaking treatment on the content of Ca²⁺in wheat leaves and the expression of key genes in calcium signal transduction pathway under the feeding stress of Schizaphis graminum（Rondani）The results of the study on the content of Ca²⁺and the expression of key genes in calcium signal transduction pathway in wheat leaves under different treatments showed that:（1）There was no significant difference in the content of Ca²⁺with water soaked the wheat plant leaves on before and after feeding by Schizaphis graminum（Rondani）,while the content of Ca²⁺in the leaves of wheat plants soaked with CaCl₂ was significantly higher after being fed by Schizaphis graminum（Rondani）than before;in the absence of Schizaphis graminum（Rondani）feeding,the Ca²⁺content in the wheat leaves of the CaCl₂ seed soaking treatment was significantly higher than that of the water soaking treatment by 20.00%,after 24 h,48 h and 72 h of Schizaphis graminum（Rondani）feeding,the Ca²⁺content in the leaves of the CaCl₂soaked wheat plants was17.80%,20.15%and 35.75%higher than that of the water soaked wheat plants,respectively;（2）In the absence of Schizaphis graminum（Rondani）feeding,there was no significant difference in the expression of TaCaM in the leaves of wheat plants with different treatments,while the expressions of TaCDPK and TaCIPK in the leaves of wheat plants treated with exogenous calcium were significantly higher than those of the control treatments;after 24 h,48 h and 72 h of Schizaphis graminum（Rondani）feeding,the expression of TaCaM,TaCDPK and TaCIPK in wheat leaves of different treatments were significantly up-regulated after fed with Schizaphis graminum（Rondani）,and the expression levels of TaCaM,TaCDPK and TaCIPK genes in wheat leaves treated with CaCl₂ was significantly higher than those of wheat soaked with water,the expression of TaCaM reached the maximum at 24 h,which was 3.17 times higher than that of water soaked wheat,and TaCDPK and TaCIPK gene expression reached the maximum at 48h,which were 1.84 and 2.40 times that of water soaked wheat,respectively.The above results indicate that CaCl₂ treatment promoted calcium signal transduction and calcium deposition in leaves.3 Effects of seed soaked with exogenous calcium on callose deposition in wheat leaves under feeding stress of Schizaphis graminum（Rondani）The results of callose deposition in wheat leaves under different treatments showed that:（1）In the absence of Schizaphis graminum（Rondani）feeding,there was no significant difference in the content of callose in the leaves of wheat plants under different treatments,the callose content in the leaves of wheat plants of all treatments increased significantly after after feeding on the wheat Schizaphis graminum（Rondani）,the content of callose in the leaves of wheat plants treated with CaCl₂ was 53.72%,33.70%and 50.42%higher than that of wheat plants treated with water at 24 h,48 h and 72 h,respectively;（2）In the absence of Schizaphis graminum（Rondani）feeding,there were no significant differences in the expression levels of callose synthase genes TaGSL8,TaGSL12,TaGSL22 and TaGSL23 among different treatments,while the expression levels of TaGSL2,TaGSL10 and TaGSL19 in wheat plants soaking with CaCl₂ were significantly higher than those in wheat plants soaking with water.After Schizaphis graminum（Rondani）ingested,the expression levels of TaGSLs in wheat leaves under different treatments were significantly up-regulated,and the expression level of TaGSLs in leaves of wheat plants treated with CaCl₂ seed soaking was significantly higher than that of wheat plants treated with water soaking at each feeding time period,TaGSL8,TaGSL10,TaGSL19,TaGSL22 and TaGSL23 reached the maximum value at 48 h,TaGSL2 and TaGSL12 reached the maximum value at 72 h;（3）Observe the deposition of callose in wheat leaves through frozen sections,the callose deposits were mainly in the phloem,the deposition area of callose in leaves of wheat plants treated with CaCl₂ seed soaking was significantly higher than that of wheat plants treated with water soaking before and after feeding by Schizaphis graminum（Rondani）.The above results show that the deposition of callose hinders the feeding of the phloem of Schizaphis graminum（Rondani）,the CaCl₂ seed soaking treatment is beneficial to promote the rapid and massive deposition of callose in the phloem and prevent the aphid from uptake of nutrients in the phloem of the plant.In summary,the results of this paper show that treating wheat with CaCl₂ by soaking seeds at the seed stage can significantly promote Ca²⁺signal transmission,calcium deposition and callose synthesis in wheat leaves and significantly improve the resistance of wheat to wheat bifurcate aphid.This study will provide a theoretical basis for the use of exogenous calcium to enhance their resistance to insects,reduce the application of chemical pesticides of wheat aphids.