Effect of phosphate-solubilizing bacteria on the gene expression and inhibition of bacterial fruit blotch in melon

Pathogenic bacteria Acidovorax avenae subsp. citrulli can cause bacterial fruit blotch (BFB) in melon (Cucumis melo L.). However, the process in which melon plant inoculated with biocontrol bacteria cope with A. citrulli invasion remains unclear. This study aimed to analyze the expression of genes involved in the BFB with a biocontrol strain through RNA sequencing. Results showed that the disease incidence of BFB was reduced by 57.1 % when melon was inoculated with antagonistic phosphate-solubilizing bacteria (PSB) Burkholderia sp. 'N3' strain. The plant height, dry weight, leaf area, and uptake of nutrients of melon seedlings increased after it was inoculated with two strains ('N3' and 'M01'). The P content in TN (inoculated with 'N3') significantly increased by 17.48 % compared with the control (TR1). Fe3+ significantly increased in melon plant inoculated with 'N3' and 'Pslb24' and might play an important role in the suppression of BFB in melon. A total of 129 upregulated genes and 33 downregulated genes were involved in the resistance of melon to A. citrulli infection (TP2 versus TP1). Gene ontology analysis revealed that most differentially expressed genes were located in biological regulation, cell component organization, binding, and catalytic activity functions. Kyoto Encyclopedia of Genes and Genomes analysis illustrated that pathways related to cell cycle, ribosome biogenesis, plant hormone signal transduction, starch and sucrose, and signal transmission mechanisms were involved. These findings will be helpful to elaborate and uncover the expression of resistance genes involved in controlling BFB in melon inoculated with beneficial PSB.