Abstract
The fall armyworm (FAW), Spodoptera frugiperda, is a destructive pest native to America and has recently become an invasive insect pest in China. Because of its rapid spread and great risks in China, understanding of FAW genetic background and pesticide resistance is urgent and essential to develop effective management strategies. Here, we assembled a chromosome-level genome of a male FAW (SFynMstLFR) and compared re-sequencing results of the populations from America, Africa, and China. Strain identification of 163 individuals collected from America, Africa and China showed that both C and R strains were found in the American populations, while only C strain was found in the Chinese and African populations. Moreover, population genomics analysis showed that populations from Africa and China have close relationship with significantly genetic differentiation from American populations. Taken together, FAWs invaded into China were most likely originated from Africa. Comparative genomics analysis displayed that the cytochrome p450 gene family is extremely expanded to 425 members in FAW, of which 283 genes are specific to FAW. Treatments of Chinese populations with twenty-three pesticides showed the variant patterns of transcriptome profiles, and several detoxification genes such as AOX, UGT and GST specially responded to the pesticides. These findings will be useful in developing effective strategies for management of FAW in China and other invaded areas.
Highlights
The fall armyworm (FAW), Spodoptera frugiperda, is a devastating and highly migratory insect herbivore native to tropical and sub-tropical areas in America, and was first reported more than 100 years ago in the USA as a damaging pest to maize and other crops (Hinds and Dew, 1915)
We identified 240 samples by using TpiE4-183, including 163 resequencing samples, 72 RNA-seq samples used for pesticide resistance analysis, one sample used for genome assembly survey, one sample used for single tube long fragment read (stLFR) genome assembly, one sample used for High-throughput chromosome conformation capture (Hi-C) sequencing and two RNA-seq samples used for gene annotation (Tables S1 and S20)
FAW is frequently controlled by Bacillus thuringiensis (Bt) crops in America, where the insect pest is originally from, and may have developed multiple resistance to pesticides, but biological agents and transgenic crops as well (Morillo and Notz, 2001; Santos-Amaya et al, 2016)
Summary
The fall armyworm (FAW), Spodoptera frugiperda, is a devastating and highly migratory insect herbivore native to tropical and sub-tropical areas in America, and was first reported more than 100 years ago in the USA as a damaging pest to maize and other crops (Hinds and Dew, 1915). FAW invasion has been reported in more than 100 countries worldwide (Fig. S1). FAW larvae may attack more than 350 host plant species belonging to 76 plant families (Montezano et al, 2018), causing serious damage to crops including maize, rice, sugarcane, sorghum, and cotton (Sparks, 1979). In January 2019, FAW was first reported in Yunnan Province of China (Jing et al, 2019), and rapidly spread to 13 provinces and cities (Yunnan, Guizhou, Sichuan, Chongqing, Guangxi, Guangdong, Hainan, Hunan, Hubei, Fujian, Zhejiang, Jiangxi and Henan) of China within only four months (Wu et al, 2019). The recent FAW invasion in China has caused tremendous losses of agricultural production in the invaded regions and has become a great threat to the corn production in eastern China, the major regions of corn production in China (Li et al, 2019)
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