Effects Of Solanum Nigrum L. On Growth And Development And Symbiotic Bacteria Of Aphis Gossypii Glover

Cotton aphid（Aphis gossypii Glover）is an important cotton pest,which seriously affects the growth,yield and quality of cotton（Gossypium spp）.As a result of long-term adaptation,it has developed host specialization to cotton.Nightshade（Solanum nigrum L.）,small thistle（Cirsium setosum）and so on are not only dominant weeds in cotton field,but also important intermediate hosts of A.gossypii.Therefore,the study of host transfer between cotton and weed is helpful to explore the basic theory of new biological control.In this study,through transplanting A.gossypii to live on weed hosts for one or more generations,combined with transcriptome sequencing and microbial diversity analysis,the changes in the expression of metabolisms-related genes and the changes in the community of symbiotic bacteria after the transfer of A.gossypii were understood,so as to reveal the adaptive changes of A.gossypii in the process of host transfer.The results of this study are of great significance for the establishment of a new biological control system for cotton aphid.The main results of this study are as follows:（1）The development duration of nymph on cotton was 5.17 d,when the aphids were transferred from cotton to small thistle,the period extends to 6.51 d.The duration of this period was 5.90 d and 5.52 d for split leaf morning glory and nightshade respectively.The life span of cotton aphid transferred to split leaf morning glory was14.46 d,which was slightly shorter than that of cotton.The life span of cotton aphid transferred to small thistle and nightshade was 9.59 d and 10.78 d.The reproductive capacity of cotton aphid on the four hosts was in descending order:cotton（32.43）>nightshade（23.71）>split leaf morning glory（20.21）>small thistle（9.56）.Meanwhile,the intrinsic growth rate（r）,net productivity rate（R₀）and weekly growth rate（λ）were cotton>nightshade>split leaf morning glory>small thistle.Therefore,A.gossypii could complete its development on all four host plants.However,after the transfer of host,A.gossypii had the best fitness and feeding ability on S.nigrum,followed by split leaf morning glory,and had the worst adaptability on C.setosum.（2）Cotton aphid was transferred to S.nigrum for 1-10 generations.At the first generation（T1）,its adaptability was weak,which showed that the development duration of nymph was extended to 5.60 days,and the fecundity was reduced to 22.59（the mean nymph-laying per female）.In the 5th and 6th generation（T5 and T6）,the development duration of nymphs of T5（4.90 d）was significantly shorter than that of cotton,the oviposition duration and total life span of T5 were significantly increased,and the reproductive capacity of T5 increased to 35.61.The cotton aphid showed a process of adapting to the new host gradually with the growth of the cotton aphid on the nightshade.In addition,when the cotton aphid domesticated by the nightshade was transferred to the original host cotton,the oviposition duration and reproductive capacity increased,and it showed the highest net proliferation rate in the shortest average generation time.（3）Using transcriptome sequencing technology,the transcriptome data of cotton aphid living on cotton（M）and cotton aphid living on the first,fifth and tenth generations（T1,T5,T10）were analyzed.By comparing the differentially expressed genes among different groups,compared with the M group,there were 1928,494 and1198 differentially expressed genes in the T1,T5 and T10 groups,respectively,and 216differentially expressed genes in the T1,T5 and T10 groups.Comparison among T1,T5 and T10 groups revealed a total of 15 genes with differential expression changes.16 metabolism-related genes were obtained by annotation and enrichment analysis of differentially expressed genes in each sample,most of which were down-regulated in T1 and T10 groups and up-regulated in T5 group.（4）According to 16S amplicon sequencing,the symbiotic communities of all aphid samples were annotated into 18 phyla,33 classes,75 orders,116 families and 168genera.Compared with A.gossypii on cotton（M）,the diversity and richness of bacterial community of adults were changed when they transferred to the nightshade for different generations（T1,T5,T10）.The dominant bacteria at the phylum level were Proteobacteria.However,at the genus level,the facultative symbiosis Arsenophonus and Buchnera were the dominant bacteria in the bacterial community composition of group M.Compared with group M,the bacterial community composition of group T1showed little change,while the number of Buchnera in groups T5 and T10 increased significantly.Therefore,the bacterial community diversity and composition changed little when the cotton aphid was transferred to the nightshade for the first generation,and it changed significantly when the aphid was fed on the nightshade for the fifth and tenth generations.