Study On Resistance Mechanism Of Wheat To Sitobion Avenae F Induced By Silicon Application

Aphid is a pest that causes serious damage on wheat globally,especially in the Huang-Huai wheat production area in China.Sitobion avenae F and Rhopalosiphum padi L are the dominant wheat aphids species in the Huang-Huai wheat production area.Sitobion avenae F is the dominant species in wheat seedling.Silicon plays an important role in the insect resistance of plants as an inducing factor.This study based on both aphids response and wheat resistance includes the effect of silicon application on the development and reproduction and the selection behaviors of aphids,basic metabolism,secondary metabolism,signal transduction,phloem response,internal metabolic pathway and resistance gene change of wheat.To investigate the resistance mechanism of wheat to Sitobion avenae F induced by silicon application:Our results showed:1.On the 4th and 8th day after aphids infection,the density of aphids on wheat plants treated with different forms of silicon was significantly lower than that without silicon,and the silicon and soluble sugar contents in wheat increased significantly,respectively.TEOS treatment significantly increased by 69.05%,77.05%;18.50%,36.69%;the contents of free amino acids and soluble proteins decreased significantly by 45.16%,78.16%;48.82%,95.26%,respectively.2.The physiological metabolic mechanism of different concentrations of silicon that improve wheat aphids resistance was explored by using the selected silicon forms.Compared with CK treatment,silicon treatment could significantly reduce the net growth rate(R0),intrinsic growth rate(rm),average generation cycle(T),and weekly growth rate(?)of aphids,and prolong the population doubling time(t)by 3.69%,6.85%,8.61%,6.63%,4.01%,respectively;the silicon content of wheat increased significantly by 13.75%,33.04%,43.98%,55.13%,34.57%,18.75%and 14.16% respectively;the activity of phenylalanine ammonia-lyase(PAL),polyphenol oxidase(PPO),catalase(CAT)and lipoxygenase(LOX)in wheat were increased,and the contents of signal transduction substances(salicylic acid(JA),jasmonic acid(SA))and secondary metabolites(tannins,alkaloids,lignin,total phenols and total flavonoids)were increased.The activity of defense enzymes,secondary metabolism,signal transduction substances and silicon content in wheat were negatively correlated with R0,T,rm,and positively correlated with t.Silicon application could reduce the growth and reproduction rate of aphids by increasing the silicon content in wheat,enhancing the signal transduction and secondary metabolic pathway of wheat,thus improving the resistance of wheat.3.Silicon application increased the number of np and pd waves after aphids infection,prolonged the duration of np,pd and E1 waves,shortened the duration of E2 and G waves,increased the individual ratio of F and G waves,the ratio of np and pd waves,and reduced the proportion of feeding waves.Silicon application could increase callose content,per area and enzyme activity,and reach the highest at 24 h,prolong the duration of ethylene release after aphids infection,the gene expression of Ta MYB44,Ta MYB29,GSL2-F,GSL10-F,EIN2 and CALS2-F in wheat was significantly up-regulated and reached the maximum at 24 h.Compared with CK treatment,Si A treatment could significantly increase the gene expression by 15.22,0.77,32.73,5.45,0.55 and 4.62 times,respectively.The gene expression of Ta MYB70 was significantly up-regulated at 72 h.Compared with CK treatment,at 72 h,the other treatments were significantly up-regulated by 4.96,2.55,and 9.28 times,respectively.4.Silicon application increased the up-regulation and down-regulation of gene expression after aphids infection,which increased by 0.95 and 2.04 times respectively,GO database annotates those differential genes selected between silicon application and non-silicon application treatments.The results showed that silicon application affected 1,3-D-glucan anabolism,aldehyde synthesis pathway,oxidase activity and active oxygen,terpene gas content and plant metabolism processes,including glucan metabolic process,lignin metabolic process and indole-containing compound metabolic process.Silicon application could specifically up-regulate the pathways significantly enriched by differential genes in KEGG annotation analysis,such as amino sugar and nucleotide sugar metabolism,pentose phosphate pathway,fatty acid biosynthesis,etc.,caused corresponding changes in resistance substances,thereby improved wheat resistance to aphids.It had revealed the intrinsic molecular mechanism of silicon application improving wheat resistance to wheat aphids.This study preliminarily clarified the synergistic mechanism behind the interaction of silicon application-wheat-aphids(Sitobion avenae F).The effects of silicon application on the growth,reproduction and feeding of aphids were clarified,and the physiological metabolism,phloem defense response and internal molecular mechanism of wheat defense against aphids were explored.Our results set a foundation for further study on the mechanism of plant resistance to aphids induced by exogenous compounds.