Analysis of the Changes in Diversity of Culturable Bacteria in Different Niches of Mulberry Fields and Assessment of Their Plant Growth-Promoting Potential

Microorganisms play a crucial role in agricultural systems. The use of plant growth-promoting bacteria (PGPB) to enhance agricultural production in a sustainable and environmentally friendly manner has been widely recognized as a key technology for the future. In this study, we analyzed the diversity changes of bacteria in different ecological niches of mulberry fields based on culture-dependent methods, and we further evaluated their antibacterial and plant growth-promoting (PGP) activities. A total of 346 cultivable bacteria belonging to 30 genera were isolated from mulberry rhizosphere soil, mulberry plants and silkworm intestines, among which the dominant genera were <i>Bacillus</i>, <i>Pseudomonas</i>, and <i>Enterobacter</i>. The bacterial communities in the mulberry rhizosphere soil were more diverse than those in the mulberry endophytes and in the silkworm intestines. The antibacterial test showed that 30 bacteria exhibited antibacterial activity against the plant pathogen <i>Ralstonia solanacearum</i>. PGP trait assays indicated that 58 bacteria were capable of nitrogen fixation, phosphate solubilization, potassium release and siderophore production simultaneously. The screened functional strains promoted the growth of mulberry saplings. The results of this study highlight new findings on the application of silkworm intestinal bacteria in PGPB.