Transcriptome analysis of growth and quality response of chrysanthemum to co-inoculation with Bacillus velezensis and Pseudomonas aeruginosa.

• Bacillus velezensis and Pseudomonas aeruginosa were isolated and identified from rhizosphere soils obtained from different chrysanthemum production bases. • PGPRs significantly enhance the growth and nutrient accumulation of chrysanthemum. • Co-inoculation with both PGPRs demonstrates enhanced plant growth and quality in chrysanthemums compared to single PGPR strain inoculation. However, it appears that Bacillus velezensis plays a dominant role in growth. • PGPRs regulate metabolic pathways and growth hormone signaling pathways in chrysanthemums. • PGPR induces gene expression in cellular metabolism, signal transduction, and probiotic substance synthesis. The inoculation of plants with plant growth-promoting rhizobacteria (PGPR) has been increasingly discussed as a way to sustainably promote plant growth and soil health. Although some promising results have been achieved in the laboratory, the applications of microbial inoculants in chrysanthemum production greenhouses and co-inoculation with PGPRs in ornamental planting systems have been less investigated. Here, greenhouse experiments were conducted to study the integrated effect of bioagents (Bacillus velezensis and Pseudomonas aeruginosa) on chrysanthemum nutrient use efficiency, plant growth, and quality. The growth-promoting mechanisms were further elucidated by transcriptome analysis. Co-inoculation with the two PGPRs increased the absorption and utilization of nitrogen, phosphorus, and potassium. The quality and growth of chrysanthemum were significantly higher than those of single PGPR inoculation or soil conditioner application. Transcriptome analysis revealed that differentially expressed genes (DEGs) were co-expressed at 30, 60, and 90 days after chrysanthemum co-inoculation with the two PGPRs. DEGs were primarily enriched in metabolic and signal transduction pathways. PDC encoding pyruvate decarboxylase in the glycolysis pathway and SAUR32 and SAUR36 encoding auxin were upregulated in chrysanthemum during the PGPRs inoculation period. Notably, the transcription factors WRKY70 and BHLH35 belonging to signal transduction and defense responses were both upregulated, demonstrating that chrysanthemum system and disease resistance were activated. The results of this study could help to elucidate the mechanism of 2 PGPRs on chrysanthemum growth and development at the transcriptome level, which could lay a theoretical foundation for the highly efficient cultivation of cut chrysanthemum "Qinhuai Yulian". [ABSTRACT FROM AUTHOR]