Suppression of Pseudomonas syringae pv. tomato infection by rhizosphere fungi.

Abstract

BACKGROUND\nInduced resistance against several plant pathogens was reported using different beneficial plant growth promoting microorganisms. The potential of 5 fungal isolates, Trichoderma harzianum GT 3-2, Fusarium equiseti GF 18-3, Fusarium equiseti GF 19-1, Phoma sp. GS 10-1 and Phoma sp. GS 14-1, was evaluated to stimulate tomato growth and resistance against bacterial speck disease caused by Pseudomonas syringae pathovar (pv.) tomato DC3000.\n\n\nRESULTS\nBased 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 six days after pathogen inoculation.\n\n\nCONCLUSION\nTaken 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 genes expression reveals significant activation in both BGI and CF treatments, leading to stimulated resistance against the pathogen.