Biocontrol of bacterial fruit blotch by seed priming with Bacillus amyloliquefaciens and Pseudomonas fluorescens

Bacterial fruit blotch (BFB), caused by the seed-transmitted pathogen Acidovorax citrulli, poses a serious threat to cucurbitaceous crops worldwide. In this study, two biocontrol bacteria strains, Bacillus amyloliquefaciens (Ba-2) and Pseudomonas fluorescens (2P24), with significant antagonistic activity against A. citrulli were and applied by seed priming to control BFB seed transmission. Artificially infested watermelon and melon seeds were treated with the biocontrol strains by liquid or solid matrix seed priming. The seed bio-priming effects were evaluated under greenhouse conditions. Germination percentages were improved by seed priming treatments for melon, and seedling uniformity was higher for seeds primed with Ba-2 than for seeds from the other treatments for watermelon. Seedling disease incidence of untreated seeds were 6.5% for watermelon and 16.0% for melon, and water-priming resulted in similar disease progress curves as the untreated control. Seed priming with Ba-2 and 2P24 significantly reduced seedling BFB incidence for both watermelon and melon. Evaluation with naturally infested watermelon seeds primed with biocontrol strains indicated that 2P24 seed priming was more effective than Ba-2 (P < 0.05) and 2P24 solid matrix priming, reducing the seedling disease incidence to 1.3%. Seed bio-priming has potential as an effective and eco-friendly approach for suppressing bacterial fruit blotch seed-to-seedling transmission.