Biocontrol potential of four Pseudomonas strains against tobacco black shank disease.

Tobacco black shank is a significant disease that poses a severe threat to tobacco production. To identify effective biocontrol agents for combating tobacco black shank disease, a screening of 39 putative Pseudomonas strains was conducted utilizing the plate confrontation assay. Four strains exhibiting inhibitory effects were selected and further evaluated for their disease control potential in pot trials. The effects of the strains on the growth of tobacco seedlings were detected using the root-irrigation method. The results demonstrated that four Pseudomonas strains exhibited significant inhibitory effects against tobacco black shank disease. The inhibition rates of strains YC2140, YC2090, YC2202, and Tr157 against P. nicotianae were determined to be 77.20%, 73.43%, 73.07%, and 32.46%, respectively. Pot trials showed that the biocontrol efficiency of Tr157, YC2090, YC2140, YC2202 against tobacco black shank disease was 96.30%, 66.67%, 62.96%, 62.96%, respectively. In addition, the strain Tr157 was found to be capable of producing indole-3-acetic acid (IAA). Meanwhile, Tr157, YC2140, and YC2202 demonstrated the ability to solubilize phosphorus, while all the four strains were capable of solubilizing potassium and producing siderophores. These strains also promoted tobacco growth increasing the total fresh weight by 146.33%, 153.21%, 87.16% and 239.91%, respectively. Overall, this study underscores the potential of the four Pseudomonas strains as effective biocontrol agents against tobacco black shank disease, offering an eco-friendly and sustainable alternative to chemical fungicides in agriculture.