Single-nucleotide polymorphism markers in mitochondrial genomes for identifying Varroa destructor-resistant and -susceptible strains of Apis mellifera (Hymenoptera: Apidae)

Mitogenome sequences have a high potential for possessing single-nucleotide polymorphisms (SNPs) that can be used to identify different strains of an organism bred based on maternal lines. The European honey bee, Apis mellifera ligustica (Hymenoptera: Apidae), with a high-hygienic behaviour (HHB) against the external parasitic mite Varroa destructor has been bred for several years in Korea. To distinguish this strain from low-hygienic behaviour (LHB) strains, the complete mitogenome of the two strains were sequenced using next-generation sequencing techniques to detect SNPs. The two mitogenomes with lengths of 16,449 and 16,426 base pairs (bp) in the HHB and LHB strains, respectively, contained a typical set of genes (13 protein-coding genes, 2 rRNA genes, and 22 tRNA genes, plus one non-coding region), exhibited similar-nucleotide compositions, and had an identical gene arrangement compared to other available A. mellifera mitogenomes. The major differences between the HHB and LHB strains included the length of the intergenic spacer sequences located at the COIII and trnG junction (88 vs. 70 bp) and ND4 and ND4L junction (45 vs. 33 bp) and the presence or absence of a duplicated sequence block (CTTTTTTAAAAAAATAAAAA) in the A + T-rich region. Comparison of the mitogenome sequences from the two strains of A. m. ligustica revealed 23 SNPs in 11 protein-coding genes which were confirmed by sequencing of 10 randomly selected individuals from each strain, indicating the usefulness of these SNP markers for identifying the HHB strain of A. m. ligustica. Therefore, mitogenome sequences are a promising genome source for detecting SNP markers, particularly those in inbred female lines.

Genome sequence of the Japanese oak silk moth, Antheraea yamamai: the first draft genome in the family Saturniidae

Background

Antheraea yamamai, also known as the Japanese oak silk moth, is a wild species of silk moth. Silk produced by A. yamamai, referred to as tensan silk, shows different characteristics such as thickness, compressive elasticity, and chemical resistance compared with common silk produced from the domesticated silkworm, Bombyx mori. Its unique characteristics have led to its use in many research fields including biotechnology and medical science, and the scientific as well as economic importance of the wild silk moth continues to gradually increase. However, no genomic information for the wild silk moth, including A. yamamai, is currently available.

Findings

In order to construct the A. yamamai genome, a total of 147G base pairs using Illumina and Pacbio sequencing platforms were generated, providing 210-fold coverage based on the 700-Mb estimated genome size of A. yamamai. The assembled genome of A. yamamai was 656 Mb (>2 kb) with 3675 scaffolds, and the N50 length of assembly was 739 Kb with a 34.07% GC ratio. Identified repeat elements covered 37.33% of the total genome, and the completeness of the constructed genome assembly was estimated to be 96.7% by Benchmarking Universal Single-Copy Orthologs v2 analysis. A total of 15 481 genes were identified using Evidence Modeler based on the gene prediction results obtained from 3 different methods (ab initio, RNA-seq-based, known-gene-based) and manual curation.

Conclusions

Here we present the genome sequence of A. yamamai, the first genome sequence of the wild silk moth. These results provide valuable genomic information, which will help enrich our understanding of the molecular mechanisms relating to not only specific phenotypes such as wild silk itself but also the genomic evolution of Saturniidae.

Complete mitochondrial genome of the female-wingless bagworm moth, Eumeta variegata Snellen, 1879 (Lepidoptera: Psychidae)

The complete mitochondrial genome of the female-wingless bagworm moth, Eumeta variegata Snellen, 1879 (Lepidoptera: Psychidae), is 15,660 base pairs (bp) and contains a typical set of genes (13 protein-coding genes [PCGs], 2 rRNA genes, and 22 tRNA genes) and one non-coding region, with an arrangement identical to that observed in most lepidopteran genomes. Twelve PCGs contained the typical ATN start codon, whereas COI had the atypical CGA codon, which is frequently detected in the start region of the lepidopteran COI. The A + T-rich region was unusually short with only 94 bp. A recent report of the same species originating from Japan revealed a lack of trnE and trnF and a 1,118 bp long A + T-rich region. Phylogenetic analyses with concatenated sequences of the 13 PCGs and two rRNA genes using the Bayesian inference method placed E. variegata in Psychidae, as a sister to a within-familial species, Mahasena colona, with the highest nodal support (Bayesian posterior probability = 1).

Phytosanitary Cold Treatment of Spotted-Wing Drosophila, Drosophila suzukii (Diptera: Drosophilidae) in 'Campbell Early' Grape

The effects of cold storage temperature and exposure duration on different developmental stages of spotted-wing drosophila (SWD) Drosophila suzukii (Diptera: Drosophilidae) on 'Campbell Early' grapes were examined to establish a phytosanitary control method. The immature stages (eggs, larvae and pupae) of SWD were all dead after a 6-d cold treatment at 1°C and 8-d cold treatment at 1.5 and 2°C. Probit-9 estimated a fourfold increase in cold treatment duration to achieve 99.9968% mortality, compared with the observed mortality. Efficacy tests using pupae, which were the most cold-tolerant stage, confirmed the validity of the selected temperature and exposure durations. Based on these results, 1°C, which requires a shorter exposure for complete mortality, was selected for the test in conditions that mimic those of grape exportation. Six-day cold treatments at 1°C produced 99.57%, mortality in different replicates, although the surviving pupae died later. Conversely, the 8- and 10-d treatments at 1°C showed 100% mortality, suggesting that these treatments can provide quarantine security against infestations of SWD on exported Campbell Early grapes, although an additional experiment with an increased sample size is required for further reliable conclusion.