The effect of some bacteria strains on cucumber defense reactions for controlling of Fusarium stem and root rot disease

Cucumber is one of the most important crop in Iran. Pests and pathogens are the most important factors limiting its cultivation and lead to reduced yields. Biological control is condiderd as the best control method for soil-borne disease including Fusarium stem and root rot. In this study, antagonistic effects of Pseudomonas fluorescens strains on the important root rot pathogens of cucumber with dual culture method was examined in vitro. Strain VUPf760 showed the highest inhibition zone against Fusarium oxysporium and Fusarium solani with 9 and 7 mm, respectively. Inhibitory effects of these isolates on the disease was evaluated in the greenhouse. The results showed that seeds treatment with T17-4 and VUPf5 isolates reduced the severity of disease caused by F. oxysporum and F. solani by58 and 60%, respectively. In addition, all three isolates alone increased peroxidase activity, total phenols and polyphenol oxidase in cucumber seedlings. However, the activity of these enzymes were higher in treatments with combination of antagonist and pathogen.