De novo sequencing and characterization of the Bradysia odoriphaga (Diptera: Sciaridae) larval transcriptome

The most serious pestilent threat to the Chinese chive, Allium tuberosum Rottle ex Spreng (Liliaceae) is the Bradysia odoriphaga Yang and Zhang. There is limited genetic research focused on B. odoriphaga, partially due to the lack of genomic resources. The advent of high-throughput sequencing technologies has enabled generation of genomic resources in a short time frame and at minimal costs. In this study, we performed, for the first time, de novo transcriptome sequencing of the B. odoriphaga. Here, 16,829 unigenes were assembled from the total reads, 12,024 of these unigenes were annotated in the NCBI NR protein database, and 9784 were annotated in the Swiss-Prot database. Of these annotated unigenes, 7903 and 5060 unigenes have been assigned to gene ontology categories and clusters of orthologous groups, respectively. Furthermore, 8647 unigenes were mapped to 257 pathways using the Kyoto Encyclopedia of Genes and Genomes Pathway database. We found that 408 unigenes were related to insecticide resistance and metabolism. In addition, 23,122 simple sequence repeats (SSRs) were identified in 11,009 unigenes, and 100 PCR primers of SSR loci were used to validate the assembly quality and polymorphisms. These results provide a good platform for further investigations into the insecticide resistance of B. odoriphaga. Finally, the SSRs identified in B. odoriphaga may be a useful genomic resource.