Wheat Resistance Induced By The Fall Armyworm Spodoptera Frugiperda,Feeding And Its Effect On The Grain Aphid Sitobion Miscanthi

Spodoptera frugiperda is a major agricultural pest that has invaded China in recent years,mainly affecting maize.However,its damage to wheat at the seedling stage has also caused widespread concern in some wheat and maize continuous cropping areas.The use of insect-resistant varieties is one of the safer and more effective measures in integrated pest management（IPM）strategies.In order to investigate the effect of wheat induced by the chewing pest,S.frugiperda,on the subsequent conspecifics and the piercing-sucking pest,Sitobion miscanthi,this study firstly conducted an indoor evaluation of the insect resistance of 15 main wheat varieties collected from the Yellow-Huaihai Rivers plain wheat areas,and based on the screened resistant varieties,the insect-induced resistance of wheat and its mechanism were analysed with the help of histological techniques,and finally,the broad-spectrum insect resistance induced by the insect pest was verified by evaluating the adaptation and feeding behaviour of S.miscanthi on pre-infested wheat plants of S.frugiperda.The results of this research provide a theoretical basis for the multidimensional evaluation of the effectiveness of insect-resistant varieties in integrated wheat pest management and the rational use and layout of insect-resistant varieties.The main findings of the study are as follows:1.Screening of wheat varieties with S.frugiperda-resistance characteristics.Feeding preferences of S.frugiperda for 15 wheat varieties showed that the 1st and 3rd instar larvae had higher feeding preferences for HuaiMai46,HuaiMai33,KOK1679 and TongMai6.The determination of biochemical content showed that YanNong21 leaves contained the highest levels of total phenols and tannins.Pearson correlation analysis indicated a negative correlation between larval feeding preference and total phenol and tannin content.Adaptive observations showed that larvae fed on YanNong21 had the longest developmental time.Taken together,YanNong21 has excellent resistance properties to S.frugiperda.2.Application of omics techniques to analyze the mechanisms of S.frugiperda-induced resistance in wheat.Induction of wheat by S.frugiperda larvae reduced feeding preferences and adaptation of successive conspecifics,which suggested that larval feeding induced insect resistance in wheat.Transcriptome sequencing and metabolite analysis were used to reveal the mechanism of larval feeding-induced resistance,and the results showed that the number of up-regulated genes was greater than the number of down-regulated genes after 2,6,12 and 24 h of larval feeding on wheat.The differential expressed genes（DEGs）were mainly involved in the pathways of plant hormone signal transduction,biosynthesis of secondary metabolites,and benzoxazinone biosynthesis,and most genes related to jasmonic acid（JA）,abscisic acid（ABA）and Bxs biosynthesis were significantly up-regulated,whereas SA pathway-related genes were only significantly up-regulated within 12 h of larval feeding induction.The endogenous hormones JA,JA-Ile,SA and ABA,and the typical defence substance indole,Trimboa-Glc,DHBOA-Glc,HDMBOA-Glc,HMBOA-Glc and DIMBOA in wheat also accumulated at different times of S.frugiperda induction,suggesting that the JA,SA and ABA pathways and the Bxs biosynthetic pathway in wheat mediate the insect-induced resistance mechanism in plants.3.Effects of wheat volatiles induced by S.frugiperda on the parasitoid Telenomus remus Nixon.A dynamic headspace method was used to collect herbivore-induced wheat volatiles,a gas chromatography-mass spectrometry（GC-MS）technique to identify volatile fractions,and a Y-tube olfactometer to observe the responses of the female Telenomus remus to volatiles.The results revealed a significant tendency for the female T.remus to choose wheat volatiles induced by caterpillar for 12 and 24 h.Six volatile components（E）-2-hexenal,6-methyl-5-hepten-2-one,（E）-2-nonenal,3-heptanol,limonene and methyl salicylate were significantly attractive to T.remus at 1 or 10 μL/mL.4.Effect of S.frugiperda-induced wheat plant on S.miscanthi.Compared to the control,on wheat plants pre-infested with S.frugiperda for 2 and 12 h,the population parameters of intrinsic rate of increase（r_m）,finite rate of increase（λ）and net reproductive rate（R₀）,the survival rate(s_xj)and life expectancy(e_xj)were significantly reduced,the mean generation time（T）was prolonged,and the phloem feeding time（E2 waves）was significantly shortened.The activities of the four detoxifying enzymes acetylcholinesterase（AchE）,insect cytochrome P450 oxidoreductase（CPR）,glutathione sulfotransferases（GSTs）and arboxylesterase（CarE）were all increased in S.miscanthi after it had fed on wheat plants pre-infested by S.frugiperda.This indicates that wheat resistance induced by S.frugiperda infestation inhibits the population growth of S.miscanthi and is characterized by broad-spectrum induced resistance.