The Effect of Environmental pH on the Antifungal Activity of Pseudomonas protegens CHA0 against Verticillium dahliae

Abstract

Pseudomonas protegens CHA0 is a potential biocontrol agent for root rot diseases such as Verticillium wilt, caused by several species of the Verticillium genus of fungi. However, to optimize P. protegens CHA0 for biocontrol, it is important to determine how its antifungal properties are affected by environmental conditions in agricultural settings. Soil pH, for instance, has been shown to affect both bacterial and fungal activity in vitro and in vivo. Since soil pH  can be controlled in agricultural practices, it is important to understand the effect of pH on the fungal inhibition of P. protegens CHA0 before it can be widely used as a biocontrol agent.  In this study, we used co-culturing and inhibition assays to test the inhibition of V. dahliae by P. protegens CHA0 at three different pH values: 5.3, 6.3, and 6.9. We measured the resulting inhibition diameters over a 7 day period and observed smaller inhibition rings in lower pH conditions. We found a significant difference between inhibition at different pH conditions, and evidence that lower pH values may negatively affect the antifungal activities of P. protegens CHA0.