Despite the successful application of toxins from Bacillus thuringiensis as biological control agents against pests, new toxins having higher toxicity and broad-spectrum activity to insects are identified more and more. To find new toxins, in this study, based on the whole genome sequence of novel Bacillus thuringiensis strain Bt S3076-1, ten predicted toxic genes were identified, including six cry genes, two tpp genes, one cyt gene and one vip gene, among which six were novel toxins. Subsequently, SDS-PAGE analysis showed that the major proteins at spore maturation stage were about 120 kDa, 70 kDa, 67 kDa, 60 kDa and 40 kDa, while approximately 70 kDa and 40 kDa active proteins after trypsin digestion with the LC50 of 149.64 µg/g and 441.47 µg/g against Spodoptera frugiperda and Helicoverpa armigera larvae, respectively. Furthermore, pathological observation results showed the peritrophic membrane of Spodoptera frugiperda and Helicoverpa armigera larvae was degraded. These findings will provide experimental reference for further research on insecticidal activity, toxicity spectrum as well as the synergism of these toxins in Bt S3076-1.

Despite the successful application of toxins from Bacillus thuringiensis as biological control agents against pests, new toxins having higher toxicity and broad-spectrum activity to insects are identi ed more and more. To nd new toxins, in this study, based on the whole genome sequence of novel Bacillus thuringiensis strain Bt S3076-1, ten predicted toxic genes were identi ed, including six cry genes, two tpp genes, one cyt gene and one vip gene, among which six were novel toxins. Subsequently, SDS-PAGE analysis showed that the major proteins at spore maturation stage were about 120 kDa, 70 kDa, 67 kDa, 60 kDa and 40 kDa, while approximately 70 kDa and 40 kDa active proteins after trypsin digestion with the LC50 of 149.64 µg/g and 441.47 µg/g against Spodoptera frugiperda and Helicoverpa armigera larvae, respectively. Furthermore, pathological observation results showed the peritrophic membrane of Spodoptera frugiperda and Helicoverpa armigera larvae was degraded. These ndings will provide experimental reference for further research on insecticidal activity, toxicity spectrum as well as the synergism of these toxins in Bt S3076-1. Key ContributionSpodoptera frugiperda and Helicoverpa armigera are important agriculture pests, and the long-term use of microbial pesticides can easily be prone to increase the pest resistance to Spodoptera frugiperda and Helicoverpa armigera. Finding novel Bacillus thuringiensis insecticidal strains and toxic proteins can be more effectively controled. Bt S3076-1, which was isolated from Diaoluoshan National Nature Reserve in Hainan Province, exhibited insecticidal activity against Spodoptera frugiperda and Helicoverpa armigera. Based on the whole genome sequence of Bt S3076-1, 10 predicted toxin genes were analyzed and identi ed via bioinformatics method. It will provide new resources for accurate prevention and control the agricultural lepidopteran pests. BackgroundSpodoptera frugiperda (Lepidoptera: Noctuidae, Spodoptera) is an important migratory pest, originating in tropical and subtropical America(Sparks. 1979) (Mehrkhou et al. 2012), which has the characteristics of strong reproduction, fast migration, and wide host range (Fu et al. 2017). It is a worldwide widespread pest, and its host plants include 350 species belonging to 76 families, including Gramineae, Leguminosae, and Compositae(Montezano et al. 2018). In the larval stage, they feed on corn leaves and ears, and one adult female of Spodoptera frugiperda can lay up to 2,000 eggs, which can directly damage one acre of corn. In the last two decades, severe outbreaks of this pest have been reported in many parts of Asia, Africa, Europe, and America(Zhang et al. 2008)(Ehler 2004)(Mehrkhou et al. 2012][. Helicoverpa armigera, another kind of worldwide omnivorous pest, is also a major pest in China, destroying cotton, tomato, pepper, tobacco, sun ower, corn and sorghum and other crops, causing signi cant economic losses(Chen and Liu 2021). Currently, chemical pesticides are mainly used to control lepidopterous pests like Spodop...