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The domesticated silkworm, Bombyx mori Linnaeus (Lepidoptera: Bombycidae), often poses a challenge in strain identification due to similarities in morphology and genetic background. In South Korea, around 40 silkworm strains are classified as premium, including 5 endemic tri-molting strains: Goryeosammyeon, Sammyeonhonghoeback, Hansammyeon, Sun7ho, and Sandongsammyeon. These strains have potential for breeding programs in response to emerging industry demands, necessitating a reliable strain identification method. In this study, we established a molecular diagnosis approach for these 5 strains. We selected 2–4 single-nucleotide polymorphisms (SNPs) for each strain from whole-genome sequences of 39 strains, encompassing 37 previously studied and 2 newly added. These SNPs were utilized to construct decision trees for each endemic strain identification. The SNPs can be used to distinguish each target strain from the 38 nontarget strains by the tetra-primer amplification refractory mutation system-polymerase chain reaction, with the exception of HMS which needs the addition of PCR-restriction fragment length polymorphism method at the final step. This decision tree-based method using genomic SNPs, coupled with the 2 typing methods, produced consistent and accurate results, providing 100% accuracy. Additionally, the significant number of remaining SNPs identified in this study could be valuable for future diagnosis of the other strains. [ABSTRACT FROM AUTHOR]

To meet the increasing demands of the society in the current era, new strains of the domesticated silkworm Bombyx mori Linnaeus, 1758 (Lepidoptera: Bombycidae) are being continuously bred. Consequently, cataloging the genetic information of pure lines is essential. The strain Jam 146, whose larvae have atypical pale, crescent-shaped body markings, is an important breeding resource due to its excellent fecundity. In this study, we sequenced the mitochondrial genome (mitogenome) of this strain using next-generation sequencing. The complete genome of this strain has a gene arrangement typical of Lepidoptera. The length of the Jam 146 mitogenome (15,661 bp) is well within the range reported in other B. mori strains, i.e. between 15,629 (Baiyun strain, China) and 15,676 bp (Hukpyobeom strain, South Korea). However, the total length of protein-coding genes, 3,733 codons in Jam 146 and two other silkworm strains previously reported from South Korea, is 13 codons longer than that in other B. mori strains. Phylogenetic analysis of 22 silkworm strains from nine countries showed that the Jam 146 strain forms a strong cluster with three other strains from China, Japan, and South Korea, suggesting that after their split from a common ancestor, the evolutionary divergence among the silkworm strains in these countries has been limited. [ABSTRACT FROM AUTHOR]

Simple Summary: Bombyx mandarina (Lepidoptera: Bombycidae), the presumed ancestor of B. mori, has long been a subject of study to illustrate the geographic variation in relationship to origin of B. mori. We report 37 mitochondrial genome (mitogenome) sequences of B. mori strains obtained by whole-genome sequencing and four of B. mandarina individuals obtained by Sanger sequencing from South Korea. These mitogenome sequences were combined with 45 public data to uncover the population genetic and phylogenetic relationships among regional populations of B. mandarina and their relationships to B. mori. A substantial genetic reduction in B. mori strains compared to the B. mandarina was detected, with the highest diversity detected in the Chinese origin B. mori. Chinese B. mandarina were divided into northern and southern groups, largely concordant to the Qinling–Huaihe line, and the northern group was placed as an immediate progenitor of monophyletic B. mori strains in phylogenetic analyses. The enigmatic South Korean population of B. mandarina, which has often been regarded as a closer genetic group to Japan, was most similar to the northern Chinese group, evidencing substantial gene flow between the two regions. This is the first report that the South Korean B. mandarina are closer genetically to the northern Chinese group. We report 37 mitochondrial genome (mitogenome) sequences of Bombyx mori strains (Lepidoptera: Bombycidae) and four of B. mandarina individuals, each preserved and collected, respectively, in South Korea. These mitogenome sequences combined with 45 public data showed a substantial genetic reduction in B. mori strains compared to the presumed ancestor B. mandarina, with the highest diversity detected in the Chinese origin B. mori. Chinese B. mandarina were divided into northern and southern groups, concordant to the Qinling–Huaihe line, and the northern group was placed as an immediate progenitor of monophyletic B. mori strains in phylogenetic analyses, as has previously been detected. However, one individual that was in close proximity to the south Qinling–Huaihe line was exceptional, belonging to the northern group. The enigmatic South Korean population of B. mandarina, which has often been regarded as a closer genetic group to Japan, was most similar to the northern Chinese group, evidencing substantial gene flow between the two regions. Although a substantial genetic divergence is present between B. mandarina in southern China and Japan, a highly supported sister relationship between the two regional populations may suggest the potential origin of Japanese B. mandarina from southern China instead of the Korean peninsula. [ABSTRACT FROM AUTHOR]

Recently, a new silkworm strain with a peculiar larval marking and rare cocoon colour was bred in Korea for educational learning and exhibition. In order to obtain the genetic information of the newly bred strain, Chilseongjam Bombyx mori (Lepidoptera: Bombycidae), its complete mitochondrial genome (mitogenome) was sequenced. The mitogenome is 15,660 bp in length, contains a typical set of genes, and has gene arrangement and composition typical of Lepidoptera. However, the Chilseongjam strain mitogenome is 4–36 bp longer than 19 other strains originating from other countries and 16 bp shorter than the whole genome of a Korean Hukpyobeom strain. In particular, the Chilseongjam strain has an intergenic spacer sequence that is shorter than that of the Hukpyobeom strain at the tRNAHis and ND4 junction as it has fewer microsatellite-like AT repeats. Phylogenetic analyses conducted using a total of 21 silkworm strains originating from nine countries revealed a few subgroups with moderate-to-high nodal support (80–94%). The Korean Chilseongjam strain formed a relatively strong subgroup (85%) with a Japanese strain (J106) instead of the Korean Hukpyobeom strain. [ABSTRACT FROM AUTHOR]

In Korea, a new Bombyx mori (Lepidoptera: Bombycidae) strain, which has a peculiar larval body marking was bred to draw public attention to the importance of national resources. We sequenced the complete mitochondrial genome (mitogenome) of the strain "Hukpyobeom" and phylogenetic relationships of the strain were analyzed. The complete genome of the strain comprised 15,671 bp, contained a typical set of genes of animals, and had a gene arrangement and composition typical in Lepidoptera. The newly bred "Hukpyobeom" strain had a 20-50 bp longer whole genome size, 39 bp longer protein-coding genes, and 5-23 bp shorter intergenic spacer regions compared to the other strains. Phylogenetic analyses showed the "Hukpyobeom" to form a strong subgroup together with each one Japan- and China-originated strain. A strain originating from Russia (strain name Soviet_Union_No.1) was placed as the most basal lineage, forming a sister to the remaining strains, indicating genetic divergence within B. mori. [ABSTRACT FROM AUTHOR]

Suzuki’s Promolactis moth,Promalactis suzukiella, is in the family Oecophoridae of lepidodpteran Gelechioidea. This species is native to Korea, Japan and Taiwan, but has been recently found in the eastern part of the United States. Sequence information on this genus includingP. suzukiellais nearly absent due to its small size and difficulty with identification. Therefore, we sequenced the complete mitochondrial genome (mitogenome) of the species. The 15,507-bp long complete mitogenome consisted of a typical set of genes (13 protein-coding genes, two rRNA genes and 22 tRNA genes) with one major non-coding A + T-rich region, and the typical arrangement found in most Lepidoptera. The controversial start codon for cytochrome oxidase I gene was CGA without any alternatives. The 81 bpP. suzukiellatRNALyswas longer than any other tRNAs (e.g. 60–71 bp) due to the presence of a duplicated TTCTAATG sequence located at the 3′ end of tRNALys. [ABSTRACT FROM PUBLISHER]