Pseudomonas chlororaphis YTBTa14 as a Multifunctional Biocontrol Agent: Simultaneous Growth Enhancement and Systemic Resistance Induction in Vitis vinifera Against Downy Mildew

Biological control serves as a crucial strategy for crop disease management. The biocontrol potential and plant growth-promoting effects of the strain YTBTa14 were investigated. Genetic sequencing confirmed YTBTa14 as Pseudomonas chlororaphis, which exhibited broad-spectrum antifungal activity against multiple pathogens affecting grapevine, apple, cherry, and wheat. YTBTa14 significantly enhanced the growth of wheat and grapevine, specifically increasing wheat seed germination rates and improving root and coleoptile development. In grapevine plant, significant increases in root length, stem length, and fresh weight were observed. The strain demonstrated robust adaptability and stable antagonism under varying sodium chloride (NaCl) concentrations, pH levels, and temperatures. YTBTa14 modulated plant hormone levels, elevating the content of indole-3-acetic acid (IAA), gibberellins (GA), and cytokinins (CTK). Furthermore, it effectively stimulated the production of key plant defense enzymes, including superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT). Pretreatment of grape leaves with YTBTa14 triggered plant cell defense response and upregulated the expression of defense-related genes PR1 (pathogenesis-related protein 1) and PAL1 (phenylalanine ammonia-lyase 1), thereby mitigating the severity of downy mildew disease and inducing systemic resistance. These findings demonstrate that YTBTa14 is a highly promising candidate for development as a multifunctional agricultural biocontrol agent.