To elucidate the mechanism of pyrethroid resistance in Helicoverpa armigera, the study explored three possibilities based on deltamethrin as a model pyrethroid; 1) the existence of mutations in the target site of deltamethrin, 2) the existence of variation at the genomic level between insecticide-susceptible and resistant strains, 3) differences in gene expression patterns between the strains. Based on these hypotheses, three levels of resistant strains and a susceptible strain as well as nine Korean field populations were used. As results, 1) any point mutations were not detected in sodium channel gene. 2) based on newly set Korean reference genome (GCA_026262555.1), approximately 3,369,837 and 1,032,689 variants (SNPs and Indels) were revealed from genome and ORFs, respectively. However, any specific variants were not found to be highly correlated with the level of insecticide resistance. 3) based on DEG analysis, some of detoxification enzyme genes were differently expressed particularly cytochrome P450 genes. Therefore, H. armigera possibly acquires deltamethrin resistance through a combination of actions, including over-expression of various detoxification enzymes such as CYP3 subfamilies and cuticular proteins.

The cotton bollworm, Helicoverpa armigera is one of the most polyphagous and cosmopolitan pest species in world wide including Korea. It also showed high level of resistance against various types of insecticide. To set the integrated resistant management program, first, we tried to identify the insecticide resistant mechanism via transcriptome analysis of coding and non-coding RNAs using 4 strains (Australian susceptible and resistant strains, Korean and Brazilian resistant strains, additional a sub-lethal dose insecticide treatment in Korean resistant strain). From the illumina based RNAseq data sets with genome information, some resistant involved detoxification genes and long non-coding RNAs were discovered. Second, following molecular markers were developed from resistant strain specific amino acid substitution from those candidate genes. Third, functionally identified genes’ markers were applied in field populations using some molecular diagnostic tools such as LAMP (loop mediated isothermal amplification). Now additional functional analysis is going on for these un-characterized candidate genes and long non-coding RNAs.

The genus Diadegma is a well known parasitoid group in various lepidopteran insect such as Plutella xylostella andsome are known to have symbiotic virus. Previously we reported a novel ichnovirus as named Diadegma fenestrale Ichnovirus(DfIV, 62 segments, 247,238bp) from D. fenestrale which parasitized in the P. xylostella. Here we report another ichnovirus,DsIV from Taiwan strain of D. semiclausum which parasitized in the P. xylostella. Total 64 genomic segments were sequenced,185,053bp from DsIV. Two Ichnovirus showed high similarity in 99 regions in most of segments. We already confirmedintegration of DfIV genome segments into the chromosome from the P. xylostella via genome sequencing of the lepidopteranhost. Therefore some of recombination could be passible inside of the lepidopteran genome.

The cotton bollworm, Helicoverpa armigera (Hübner) is a serious agricultural pest which has evolved resistance against many chemical classes of insecticides. This species has evolved resistance to the synthetic pyrethroids across its native range and is becoming a truly global pest, after establishing in Brazil and having been recently recorded in North America. A chimeric cytochrome P450 gene, CYP337B3, has been shown to detoxify to fenvalerate and cypermethrin. The CYP337B3 gene has now been detected in different populations around the world, and is even found in South America. This gene is likely to have arisen independently in different geographic locations, probably through selection on pre-existing diversity, and there is ongoing movement of these alleles around the world. The alleles found in Brazil are those most commonly found in Asia, suggesting a potential origin for the incursion into the Americas. This information should be taken into account when devising control strategies for this invasive pest, both in its native range and in the Americas

Insecticidal crystal toxins from the bacterium Bacillus thuringiensis (Bt) kill insects via a complex mode of action resulting in the creation of cytolytic pores in the membrane of midgut epithelial cells. These toxins are expressed in transgenic cotton and maize which have been adopted worldwide to control lepidopteran pests while reducing dependence on chemical insecticides. However, insect resistance to Bt toxins is increasing in certain key pest species. Beginning with Heliothis virescens, genetic studies in Bt-resistant Lepidoptera and Coleoptera have found mutations in ABC transporters. Cry1A, Cry1C, Cry2A, and Cry3B toxins each appear to target a different member of the ABC superfamily. These studies confirm the essential role of ABC proteins in Bt toxin mode of action. It is proposed that ABC proteins assist in the insertion of the toxin into the midgut epithelial membrane, a crucial step for which the mechanism has not been known in detail. Properties of ABC transporters suggest strategies to increase efficacy of Bt toxins and to delay the evolution of Bt toxin resistance in target insect pests.

Worldwide, increasing numbers insecticide resistant insect is one of the main problem in this agricultural era. To manage the insecticide resistance, IRAC suggest some tips for farmers : 1. Sequence or alteration of insecticide based on MOA 2. Choosing the effective insecticide. In this point raised following question : How to distinguish the effective or non-effective insecticide. Until now, bioassay is the right answer. However that is a very time-consuming, labor-intensive, and costly process, so we were hoping that molecular based diagnosis could be alternate. It can summarized following steps : 1. Identification of insecticide resistance mechanism 2. Marker development 3. Molecular diagnosis 4. Selection of non-effective insecticide. Here we focused on the development of insecticide resistance marker. Point mutation in target site of insecticide is a good example. Up or down-regulation of specific gene and/or existence of chimeric gene is another example from Helicoverpa armigera.

Capsaicin β-glucoside was isolated from the feces of Helicoverpa armigera, H. assulta and H. zea that fed on capsaicin-supplemented artificial diet. The chemical structure was identified by NMR spectroscopic analysis as well as by enzymatic hydrolysis. The excretion rates of the glucoside were different among the three species; those in the two generalists, H. armigera and H. zea, were higher than in a specialist, H. assulta. UDP-glycosyltransferases (UGT) enzyme activities measured from the whole larval homogenate of the three species with capsaicin and UDP-glucose as substrates were also higher in the two generalists. Compared among five different larval tissues (labial glands, testes from male larvae, midgut, the Malpighian tubules, and fatbody) from the three species, the formation of the capsaicin glucoside by one or more UGT is high in the fat body of all the three species as expected, as well as in H. assulta Malpighian tubules. Optimization of the enzyme assay method is also described in detail. Although the lower excretion rate of the unaltered capsaicin in H. assulta indicates higher metabolic capacity toward capsaicin than in the other two generalists, the glucosylation per se seems to be insufficient to explain the decrease of capsaicin in the specialist, suggesting H. assulta might have another important mechanism to deal with capsaicin more specifically.