Development of Isothermal Amplification Assays for the Identification of Spodoptera eridania and Spodoptera ornithogalli (Lepidoptera: Noctuidae) Using Mitochondrial Gene Sequences

Abstract

Although the southern armyworm (SAW), Spodoptera eridania, and the yellow-striped armyworm (YSAW), Spodoptera ornithogalli, have not yet been introduced to Korea, they are listed as regulated quarantine pests in Korea because of their potential to cause serious economic losses in diverse agricultural crops upon introduction. Therefore, a preemptive diagnostic method that enables rapid and accurate identification is necessary to prevent the establishment of these species. In this study, we developed loop-mediated isothermal amplification (LAMP) assays for in-field use. To develop these assays, we sequenced the complete mitochondrial genomes (mitogenomes) of the two target species, SAW and YSAW, along with that of Spodoptera praefica. By comparing the three mitogenome sequences with publicly available sequences of 11 lepidopteran species, we preferentially selected sequences suitable for designing SAW- and YSAW-specific primers for the LAMP assays from the mitochondrial cytochrome oxidase subunit I gene (COI). The assays consistently diagnosed SAW and YSAW from 13 nontarget species, including the reciprocal target species, five Spodoptera species, and seven other lepidopteran species, within 25 min of reaction time using crude DNA. These LAMP assays could serve as rapid and accurate in-field detection tools for SAW and YSAW.