Complete Mitogenomic Structure and Phylogenetic Implications of the Genus Ostrinia (Lepidoptera: Crambidae)

To understand mitogenome characteristics and reveal phylogenetic relationships of the genus Ostrinia, including several notorious pests of great importance for crops, we sequenced the complete mitogenomes of four species: Ostrinia furnacalis (Guenée, 1854), Ostrinia nubilalis (Hübner, 1796), Ostrinia scapulalis (Walker, 1859) and Ostrinia zealis (Guenée, 1854). Results indicate that the four mitogenomes—O. furnacalis, O. nubilalis, O. scapulalis, and O. zealis—are 15,245, 15,248, 15,311, and 15,208 bp in size, respectively. All four mitogenomes are comprised of 37 encoded genes and a control region. All 13 protein-coding genes (PCGs) initiate with ATN and terminate with TAN, with the exception of cox1 that starts with CGA, and cox1, cox2, and nad5 that terminate with an incomplete codon T. All transfer RNA genes (tRNAs) present the typical clover-leaf secondary structure except for the trnS1 (AGN) gene. There are some conserved structural elements in the control region. Our analyses indicate that nad6 and atp6 exhibit higher evolution rates compared to other PCGs. Phylogenetic analyses based on mitogenomes using both maximum likelihood (ML) and Bayesian inference (BI) methods revealed the relationship (O. palustralis + (O. penitalis + (O. zealis + (O. furnacalis + (O. nubilalis + O. scapulalis))))) within Ostrinia.

Susceptibility of three species of the genus Ostrinia (Lepidoptera: Crambidae) to Nosema pyrausta (Microsporidia: Nosematida)

Microsporidia are obligate intracellular parasites that affect the population density of many insect pests. In particular, infection with Nosema pyrausta is one of the major mortality factors for the European corn borer Ostrinia nubilalis, the Asian corn borer Ostrinia furnacalis and the adzuki bean borer Ostrinia scapulalis. The purpose of the work is to compare the susceptibility to N. pyrausta and pathogenesis of three species of moths of the genus Ostrinia. Studies conducted over 2 years have shown that in all three species of host insects under laboratory conditions, both during oral infection and transovarian transmission of infection (in the daughter generations of experimentally infected insects), only diplokaryotic spores formed corresponding to the main morphotype of the genus Nosema. Mean lethal time increased with instar of larvae used for infection but didn’t differ between the three species. The rates of transovarial transmission of N. pyrausta were also similar. Thus, all the insect species examined may equally participate in the parasite persistence in nature and serve as model laboratory hosts for parasitological research and mass propagation of the microsporidium.

Prevalence rates of Wolbachia endosymbiotic bacterium in natural populations of Ostrinia Nubilalis and Ostrinia Scapulalis (Lepidoptera: Pyraloidea: Crambidae) in South-Western Russia

Background. Endosymbiotic bacteria of the genus Wolbachia are widespread in arthropods and often cause reproductive abnormalities in lepidopteran insects, including corn borers of the genus Ostrinia. Wolbachia-Ostrinia is a promising model for studies of parasite-host interactions yet parasite prevalence in natural insect host populations remains unknown. Materials and Methods. Molecular genetic screening and statistical analysis is applied to evaluate prevalence rates of Wolbachia in sympatric populations of two corn borer species. Individual genomic DNA samples were extracted from last instar larvae collected in nature from different forage plants. For each sample of DNA showing positive signal with insect-specific primers the detection is performed using three diagnostic loci of Wolbachia: 16SrRNA, gatB and fbpA. Results. Wolbachia-positive signal is obtained for 13.5% larvae of Ostrinia nubilalis (N = 141) and 31.9% larvae of Ostrinia scapulalis (N = 138). In different localities the Wolbachia prevalence ranged from 2.9% (N = 34) to 65.8% (N = 38). Significantly higher rates of Wolbachia prevalence in insects from mugwort and hemp (O. scapulalis) as compared to those from corn (O. nubilalis) are revealed in three out of four localities. Conclusions. Endosymbiotic bacteria of the genus Wolbachia are revealed in natural populations of corn borers for the first time for Eastern Europe. The prevalence rates can be high and this should be taken into consideration when reproductive isolation is examined in population of these hosts as well as establishment of laboratory cultures is performed.