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Abstract

A very large number of major agricultural pests belong to the family Noctuidae, including Heliothis, Helicoverpa and Spodoptera. S. litura is the most important polyphagous pest in Asia; S. litura larvae feed on over 100 crops, and are distributed throughout tropical and subtropical parts of India, China and Japan. Here we report on the complete genome sequence and structure of this pest, which contains 439Mb and 15317 predicted protein-coding genes. Manual annotation of host plant-related gene families revealed a huge expansion of bitter receptor genes and major expansions of Cytochrome P450, Carboxylesterase and Glutathione-s-esterase detoxification class gene families. Transcriptome analysis showed that the expanded detoxification gene clusters were all inducible by toxins, resulting in a highly enhanced ability to detoxify metabolite xenobiotics associated with host plants and insecticides. Population genetic analysis of 64 individuals collected at 16 locales in three Asian countries showed frequent communication along a South India–South China–Japan axis with a high ability to fly for long distances, suggesting the way S. litura has expanded in East Asia. In its migration to diverse regions this pest must deal with varied ecological conditions, including different host plants and insecticides, to which we propose it can easily survive and adapt based on its high innate detoxification ability.