Effects Of Host Plants On The Development,Reproduction,Mating Behavior And Gut Microbiota Of Fall Armyworm (Spodoptera Frugiperda)

The fall armyworm（FAW）,Spodoptera frugiperda（Lepidoptera:Noctuidae）invaded China at the end of 2018 and thereafter it spread rapidly.FAW has the characteristics of wide host range,strong migratory ability,strong reproductive ability,rendering it the ability of causing serious damage.As a polyphagous pest,FAW is identified as a serious threat to agricultural production and food security in China.In this study,we draw on laboratory experiments to assess how different host plants（i.e.,maize,sorghum,tomato,pepper and eggplant）and artificial diet affect larval growth and adult reproduction by using the age-stage,two-sex life table method.Mating behavior in the fall armyworm that fed on different host plants（maize and sorghum）and artificial diet were researched.High-throughput sequencing technology of the metagenomics was used to analyze the composition,function and antibiotics resistance gene of gut microbiota communities of FAW larvae fed on four plants and artificial diet.The main results are as follws:1 Effects of 5 host plants and artificial diet on development and reproduction of FAWWe draw on laboratory experiments to show how different host plants（i.e.,maize,sorghum,tomato,pepper,eggplant）and artificial diet affect larval growth and adult reproduction of FAW.Results showed that FAW can’t complete its life cycle when fed on eggplant.There were significant differences in the development duration of larval stage,pupa,adult,female longevity,male longevity,survival rate and fecundity fed on different host plants.FAW attained the fastest larval development（15.21 d）on maize and the slowest（25.18 d）on pepper,FAW fed with pepper had the longest pre-adult stage（41.73 d）and the lightest pupal weight（0.1134 g）.There were significant differences fecundity of FAW fed on different diets,the mean fecundity of females fed on artificial diet was 995.22,which was significantly higher than that of those fed on tested plants.FAW had the highest net reproductive rate（R₀）,intrinsic rate of increase（r）and finite rate of increase（λ）on artificial diet.Among tested plants,FAW had the highest net reproductive rate（R₀）reared on tomato,the highest intrinsic rate of increase（r）,finite rate of increase（λ）,and the shortest mean generation time（T）on maize.Overall,FAW fitness on the 5 tested plants and artificial diet was:artificial diet>maize>tomato>sorghum>pepper>eggplant.2 Study on mating behavior of FAW fed on maize,sorghum and artificial dietDiurnal rhythms of adult mating behavior of FAW fed on maize,sorghum and artificial diet were researched.The results showed that mating activity occurred from21:00 to 5:00,and had only one mating peak when FAW fed on maize,sorghum and artificial diet:the peak appeared five hours after lights out and peaked from 00:00 to1:00.The mating onset time and mating duration time were not significantly different,while the cumulative mating time of sorghum-feeding（263.68±27.98 min）was significantly higher than maize-feeding（148.29±14.34 min）and artificial diet-feeding（188.34±18.41 min）.The mean mating frequency of sorghum-feeding was 1.74±0.18,which significantly higher than maize-feeding（1.16±0.07）and artificial diet-feeding（1.36±0.11）.The cumulative mating frequency of sorghum-feeding（2.10±0.17）was significantly higher than maize-feeding（1.15±0.07）and artificial diet-feeding（1.63±0.13）.Under the condition of four consecutive scotophase the cumulative mating rate of feeding on maize,sorghum and artificial diet were not significantly different,which the cumulative mating rate of feeding on sorghum（88.19±3.49%）was the highest,followed by maize-feeding（70.92±16.72%）,and artificial diet-feeding was the lowest（69.48±6.92%）.3 Comparative analysises of microbial community structure,function and antibiotic resistance gene in the gut of FAW fed on different host plantsWe determined the differences of gut microbiota structure,function and antibiotic resistance gene when FAW was transferred from an artificial diet to different host plants（maize,sorghum,tomato,pepper）by metagenomics sequencing technology.The results showed that sorghum-feeding FAW larvae had the highest richness and diversity of gut microbiota,while FAW larvae fed on maize had the lowest richness and FAW fed on pepper had the lowest diversity.We identified Firmicutes as the most dominant bacterial phyla and Enterococcaceae was the main dominant family in the gut microbiota of FAW larvae.PCo A and NMDS analysis revealed that there were significant differences in the gut microbial community structure of FAW reared on different host plants.KEGG database annotation indicated that metabolic is the major pathway in FAW gut microbiota,which carbohydrate metabolism and amino acid metabolism are main subfunctions.LEfse（LDA effect size）was used to further annotate KO in metabolic pathways.KO in sorghum group was mainly involved in peptide/nickel transport system permease protein and in pepper group was mainly 6-phospho-beta-glucosidas gene.There were20 ARGs（antibiotic resistance gene）were identified in the gut microorganisms,including van RC,efr A,efr B,van XYC and van SC.Van RC in maize-feeding gut microbiota had the highest abundance（16.43%）.These ARGs mediated resistance to antibiotics such as glycopeptide,macrolide,fluoroquinolone,rifamycin and rifampicin antibiotic,respectively.In summary,FAW is capable of completing its whole life history when fed on tomato and pepper.There were signifiant differences in the cumulaticve mating time,frequency of mating and cumulative mating times fed on maize,sorghum and artificial diet.Gut microbial structure of FAW larvae can be influenced by host plants,which affects gut microbiota functional and antibiotics resistance genes and may play an important role in host adaptation.This research provides a theoretical basis for adaptability mechanism of FAW to hosts.