The cell-free supernatant of Pseudomonas protegens CHA0 may not be sufficient to inhibit Verticillium dahliae growth

Abstract

Verticillium dahliae is a fungal pathogen that lives in agricultural soil and causes the disease known as Verticillium wilt. This disease affects over 400 species of plants, including important food sources such as potatoes, peppers, and strawberries. Currently, broad-spectrum soil fumigation is the standard treatment for Verticillium wilt, but there is a need for more sustainable and environmentally friendly alternatives. Certain Pseudomonas species are ubiquitous in agricultural soil and have been proposed as biocontrol agents to replace or supplement traditional chemical fungicides. Fluorescent pseudomonads, in particular, characteristically produce an array of antimicrobial metabolites including 2,4-diacetylphloroglucinol, pyoluteorin, and hydrogen cyanide, which exhibit strong antifungal activity. Specifically, the fluorescent Pseudomonas protegens CHA0 has been shown to be a strong inhibitor of Verticillium spp. growth, likely due to its ability to produce 2,4-diacetylphloroglucinol. Here, we investigate the ability of intact P. protegens CHA0 to inhibit V. dahliae growth and evaluate whether P. protegens CHA0 secretions alone are sufficient to inhibit V. dahliae growth. Our results demonstrated that intact P. protegens CHA0 can inhibit V. dahliae growth, but suggest that bacterial secretions alone may not be sufficient for biocontrol. Findings from this study can provide insights into effective strategies for biocontrol of plant diseases.