Abstract: 【Aim】This study aims to analyze the changes of intestinal bacterial communities in Bombyx mori larvae and the correlation between the key intestinal bacteria and the pupal weight and cocoon layer weight under different rearing patterns of artificial diet instead of mulberry leaves, so as to provide theoretical basis for the practical application of rearing B. mori by the method of partial artificial diet replacement of mulberry leaves.【Methods】B. mori larvae were reared under five different patterns including reared on mulberry leaves for all instars (Mul1-5), reared on artificial diet for the 1st-2nd instars and mulberry leaves for the 3rd-5th instars (Art1-2), reared on artificial diet for the 1st-3rd instars and mulberry leaves for the 4th-5th instars (Art1-3), reared on artificial diet for the 1st-4th instars and mulberry leaves for the 5th instar (Art1-4), and reared on artificial diet for all instars (Art1-5), and the whole cocoon weight, cocoon layer weight and pupal weight were calculated. The intestinal samples of the 5th instar larvae of B. mori under the five different rearing patterns were collected and their differences in composition and diversity of intestinal bacteria were analyzed by the high-throughput sequencing method. The correlation between the intestinal bacteria and the pupal weight and cocoon layer weight was analyzed by the Spearman correlation heatmap analysis. 【Results】The rearing patterns combining artificial diet with mulberry leaves had significant effects on cocoon quality of B. mori. The whole cocoon weight of Mull1-5 and Art1-5 was the highest, showing no significant difference, followed by that of Art1-2. The cocoon layer weight of Mul1-5 was the highest, followed by that of Art1-2, and that of Art1-5 was the lowest. The diversity and composition of intestinal bacteria in B. mori under the five rearing patterns were significantly different. At the phylum level, the bacterial composition of Art1-2 and Mul1-5 were the most similar, with the dominant bacteria of Proteobacteria and Firmicutes, while the bacterial composition of Art1-3, Art1-4 and Art1-5 was the most similar， of which the abundance of Proteobacteria gradually increased with the prolonged feeding time of artificial diet, and the abundance of Firmicutes showed an opposite trend. At the genus level, Pseudomonas, Enterococcus, Sphingomonadaceae unclassified and Ralstonia were the dominant bacteria in all groups. The abundance of the intestinal bacterial genus Enterococcus showed the largest difference in B. mori under different rearing patterns, being the highest in Art1-2 (40.9%) and decreasing gradually with the prolonged feeding time of artificial diet, and only accounting for 0.02% in Art1-5. Most of the key intestinal bacteria in B. mori were related to cocoon quality. Coxiella showed a significantly positive correlation with pupal weight, and a significantly negative correlation with cocoon layer weight. Staphylococcus was significantly negatively correlated with the pupal weight, and Enterococcus was significantly positively correlated with cocoon layer weight. 【Conclusion】The rearing pattern of Art1-2 is the closest to that of Mul1-5, which can provide reference for rearing B. mori with artificial diet partially replacing mulberry leaves. The structure of intestinal bacteria significantly change when mulberry leaves are partially replaced by artificial diet, and the significant decrease in the abundance of Enterococcus and increase of Pseudomonas may be related to the weak physique of B. mori fed with artificial diet for all instars. Some of the key bacteria are significantly correlated with pupal weight and cocoon layer weight of B. mori, although the mechanism needs further study.

Key words: Bombyx mori, artificial diet, mulberry leaves, intestinal bacteria, cocoon production performance