Inoculation with PGPR co-fermented broths promotes growth, yields, and quality of pepper by increasing soil nutrients and changing soil bacterial community.

Aims: The purpose of this study was to explore impacts of different combinations of co-fermentation plant growth-promoting rhizobacteria (PGPR) broth on the growth and yield of pepper.

Methods and results: The effects of co-fermentation broth containing a random combination of two PGPR strains on the growth of pepper were analyzed. All inoculation treatments promoted growth, yield, and quality of peppers. The relative abundance of the dominant Proteobacteria and Sphingomonas was significantly higher in the planted soil at the seedling and fruiting stages, and the soil available nitrogen, phosphorus, and potassium contents were correspondingly higher. In addition, the co-fermented broth of Bacillus velezensis HP9 and Burkholderia pyrrocinia P10 treatment had the most pronounced effect on plant growth, while the combination of Bacillus flexus HGD12 and P10 had the greatest impact on fruit nutritional indices. This is consistent with the highest enrichment of beneficial bacterial genera at the seedling stage in the HP9 and P10 treatment and at the fruiting stage in the P10 and HGD12 treatment groups, respectively.

Conclusions: Different combinations of co-fermented bacterial broths increased soil nutrient contents and changed the bacterial community, which in turn promoted the growth, yield, and quality of pepper.