Pepper feeding derivative Brucella sp. in the gut of Spodoptera litura (Lepidoptera: Noctuidae) affect the growth and development of host larvae.

BLTY is a pepper cultivar that has resistance to young larvae of Spodoptera litura Fabricius, whereas FXBX is a pepper cultivar suitable for the growth of S. litura larvae. The obtained microbiomics data suggest that the BLTY leaves fed S. litura larval guts inhabited more Brucella. In this study, two Brucella spp. (2FC-4 and 2FC-15) and one Microbacterium sp. (2FC-22) were isolated from the guts of BLTY and FXBX leaf-fed S. litura, respectively. The loading of 2FC-4 and 2FC-15 reduced the survival rate, average larval weight, diet consumption, pupation rate, and emergence rate of S. litura, whereas the efficacy of 2FC-22 was in contrast with that of the two Brucella spp. By constructing the germ-free (GF) and 2FC-4, 2FC-15, or 2FC-22 mono-associated gnotobiotic S. litura larvae, we found that the loading of 2FC-4 and 2FC-15 disrupted the peritrophic membrane and midgut walls of the tested larvae. In addition, the loading of 2FC-4 or 2FC-15 increased the juvenile hormone content and decreased the ecdysone content in S. litura. The loading of 2FC-4 or 2FC-15 decreased the activities of protease, trehalose, amylase, and invertase and increased the activities of SOD, CAT, and POD. In this study, we analyzed the resistance of BLTY to S. litura from the perspective of the gut microbiota; the selected Brucella sp. can be used for the biological control of Spodoptera pests and Microbacterium sp. can be used as an additive in the daily maintenance of Spodoptera populations.