High Taxonomic and Functional Diversity of Bacterial Communities Associated with Melon Fly, Zeugodacus cucurbitae (Diptera: Tephritidae).

The next generation sequencing (NGS) approach has facilitated the investigations of gut microbiota with high throughput and resolution. The present study was focused on the taxonomic and functional characterization of bacterial community associated with different developmental stages of melon fly, Zeugodacus cucurbitae using 16S ribosomal RNA (rRNA) gene amplicons metagenomics. Z. cucurbitae is considered an invasive and most staid polyphagous pest of cucurbitaceous and other related crops. The taxonomic analysis of highly variable V3-V4 region of bacterial 16S rRNA gene sequencing indicated that the bacterial community associated with Z. cucurbitae consists of a total of 23 bacterial phyla (including unclassified and unassigned bacteria), comprising 32 classes, 69 orders, 99 families and 130 genera. Proteobacteria, Firmicutes, Actinobacteria and Tenericutes were dominant phyla of which family, Enterobacteriaceae was the most abundant in the larval and adult female stages, whereas Mycoplasmataceae was the dominant in the pupal stage. In larval stages of Z. cucurbitae, genus Providencia and Comamonas were the most abundant. However, genus Candidatus-Bacilloplasma and Klebsiella were the most dominant in pupae and adult females of Z. cucurbitae, respectively. PICRUSt analysis conducted for prediction of metabolic activities revealed that associated microbiota were involved in membrane transport, carbohydrate metabolism, amino acid metabolism, energy metabolism, replication and repair processes as well as cellular processes and signalling. The higher number of OTUs was annotated for phosphoglycerate mutase and transketolase in adult females followed by larval stages, which may support the digestive function of the microbiota in larvae and adult females. Our findings provide insights about the high variation in microbiota across developmental stages and basis for microbiota-based management strategies of fruit flies.

Genetic analysis of Bactrocera zonata (Diptera: Tephritidae) populations from India based on cox1 and nad1 gene sequences.

The peach fruit fly, Bactrocera zonata, is among the most serious and polyphagous insect pest of fruit crops in many parts of the world under genus Bactrocera. In the present study, the genetic structure, diversity and demographic history of B. zonata in India were inferred from mitochondrial cytochrome oxidase 1 (cox1) and NADH dehydrogenase 1 (nad1) sequences. The efficiency of DNA barcodes for identification of B. zonata was also tested. Genetic diversity indices [number of haplotypes (H), haplotype diversity (Hd), nucleotide diversity (π) and average number of nucleotide differences (k)] of B. zonata populations across India maintain high level of genetic diversity without isolation by distance among the geographic regions. Non-significant negative correlation between pairwise Fst and geographic distance suggests a high level of gene flow among studied populations of B. zonata. The possibility of sudden expansion of B. zonata revealed through mismatch distribution analysis as well as negative Tajima's D and Fu's Fs values further supported by star-like network of haplotypes. DNA barcoding analysis suggests that B. zonata specimens can be clearly differentiated from other species with 100% accuracy of identification. Therefore, cytochrome oxidase 1 (cox1) barcode sequences generated in the present study could be a valuable source for the rapid identification and global population genetic study of B. zonata.

Genetic analysis of oriental fruit fly, Bactrocera dorsalis (Diptera: Tephritidae) populations based on mitochondrial cox1 and nad1 gene sequences from India and other Asian countries.

The study examined the genetic diversity and demographic history of Bactrocera dorsalis, a destructive and polyphagous insect pest of fruit crops in diverse geographic regions of India. 19 widely dispersed populations of the fly from India and other Asian countries were analysed using partial sequences of mitochondrial cytochrome oxidase I (cox1) and NADH dehydrogenase 1 (nad1) genes to investigate genetic diversity, genetic structure, and demographic history in the region. Genetic diversity indices [number of haplotypes (H), haloptype diversity (Hd), nucleotide diversity (π) and average number of nucleotide difference (k)] of populations revealed that B. dorsalis maintains fairly high level of genetic diversity without isolation by distance among the geographic regions. Demographic analysis showed significant (negative) Tajimas' D and Fu's F S with non significant sum of squared deviations (SSD) values, which indicate the possibility of recent sudden expansion of species and is further supported through distinctively star-like distribution structure of haplotypes among populations. Thus, the results indicate that both ongoing and historical factors have played important role in determining the genetic structure and diversity of the species in India. Consequently, sterile insect technique (SIT) could be a possible management strategy of species in the regions.