Abstract: 【Aim】 The composition of the gut bacteria in herbivorous insects is closely related to their foods. This study aims to address the relationship and mutual adaptation between the diversity of larval gut bacteria of Plutella xylostella and its diets. 【Methods】 The gut bacterial DNA was extracted from the 4th instar larvae of P. xylostella feeding on artificial diet (S) and the larvae shifted from artificial diet to feeding on cabbage Brassica oleracea var. capitata, Chinese cabbage Brassica rapa subsp. pekinensis and cauliflower Brassica oleracea var. italic for one generation (G1C, G1CC and G1WC, respectively), and three generations (G3C, G3CC and G3WC, respectively). The diversity and abundance of gut bacteria was then analyzed based on Illumina MiSeq of the 2nd generation high-throughput sequencing technology. 【Results】 The α-diversity index analysis indicated that the gut bacterial diversity of the 4th instar larvae of P. xylostella feeding on different diets was ranked as G1WC>G1CC>S>G1C. Firmicutes was the major phylum of the gut bacteria in sample S, while the relative abundance of Firmicutes in G1C, G1CC and G1WC decreased significantly. The relative abundance of Proteobacteria increased as the major phylum in G1C and G1CC, and that of Bacteroidetes increased as the dominant phylum in G1WC. No significant differences in terms of the α-diversity index of gut bacteria of P. xylostella were observed between the 1st and the 3rd generation of larvae feeding on all the host plants. However, the relative abundance of a few bacterial phyla had significant differences between the 1st and the 3rd generation of larvae feeding on cabbage and Chinese cabbage. Compared with G1C, G3C had a significantly reduced relative abundance of Bacillales. Similarly, the relative abundance of Proteobacteria, Gemmatimonadetes and Nitrospirae in G3CC was significantly increased as compared with that in G1CC. 【Conclusion】 The gut bacterial diversity and community composition of P. xylostella larvae reared on artificial diet and different host plants vary significantly. Host plants have a great influence on the structure and composition of the gut microbes of P. xylostella, which may have a long-term adaptation process to host plants. This should be a case study for the factors that influence gut bacteria of P. xylostella, and may provide insights into the interactions between gut bacteria and different host plants.

Key words: Plutella xylostella')">Plutella xylostella, food, host plant, gut bacteria, microbial diversity, high-throughput sequencing