Suppression of Pseudomonas syringae pv. tomato infection by rhizosphere fungi

BACKGROUND Induced resistance against several plant pathogens was reported using different beneficial plant growth‐promoting microorganisms. The potential of five fungal isolates, Trichoderma harzianum GT 3‐2, Fusarium equiseti GF 18‐3, F. equiseti GF 19‐1, Phoma sp. GS 10‐1 and Phoma sp. GS 14‐1, to stimulate tomato growth and resistance against bacterial speck disease caused by Pseudomonas syringae pathovar (pv.) tomato DC3000 was evaluated. RESULTS Based on the results of disease severity and growth promotion experiments, GF 18‐3 exhibited the best results among all fungal isolates. Treatment with barley grain inocula (BGI) and culture filtrate (CF) of the isolates promoted tomato growth and suppressed the pathogen in pot trials. Furthermore, expressions of the pathogenesis‐related genes (PR‐1, β‐1,3‐glucanase A, β‐1,3‐glucanase B and LOX) were relatively higher than the control in the leaves of tomato plants treated with both BGI and CF. The transcription levels remained consistently higher than the control plants for 6 days post‐inoculation with pathogen. CONCLUSION Taken together, the results indicate that the tested fungal isolates have the potential to promote tomato growth and induce systemic resistance against the bacterial speck disease. Analysis of certain PR gene expression revealed significant activation in both BGI and CF treatments, leading to stimulated resistance against the pathogen. © 2021 Society of Chemical Industry. Treatment with barley grain inocula (BGI) and culture filtrate (CF) of the isolates promoted tomato growth and suppressed the pathogen in pot trials. Furthermore, expressions of the pathogenesis‐related genes were relatively higher than the control in the leaves of tomato plants treated with both BGI and CF treatments.