Ethyl acetate extract of Streptomyces spp. isolated from Egyptian soil for management of Fusarium oxysporum: The causing agent of wilt disease of tomato

Tomato crops faced dangerous problems due to their attack by Fusarium oxysporum f. sp. lycopersici, the causing agent of wilt disease. Chemical treatments of such diseases caused many hazardous impacts to soil and human. For this reason, the biological control is considered as an alternative and sustainable tool for curing several plant diseases. The present work is undertaken with the aim of treating Fusarium-contaminated tomato seeds with ethyl acetate extracts from isolated Steptomyces spp., in greenhouse studies. Fifteen Steptomyces spp., isolated from native tomato rhizospheric soils, were evaluated for their antagonistic potential against Fusarium wilt pathogen. Three isolates that exhibited higher antagonistic effect were molecularly identified. Their ethyl acetate extracts (EAE) exhibited antifungal activity against the target pathogen, with higher potential with S. carpaticus EGY-S7 strain. Greenhouse assay indicated that seed treatment by the selected EAE of Steptomyces spp., isolates significantly reduced disease severity and possessed seedlings growth promoting potential of tomato ranging from 72.6 to 83.0% compared to infected control (63.4%) and chemical fungicide (76.2%). Accordingly, strain S. carpaticus EGY-S7 showed higher control efficacy (83.0%) as well as significantly increased the biomass of tomato seedlings (plant height, leaves number, fresh and dry weight) compared to a positive control (with infested soil). Additionally, it was superior to other strains, in which total polyphenols, polyphenoloxidase and peroxidase enzymes were significantly enhanced in tomato seedlings compared with untreated-infected control. Gas chromatography-mass spectrometry (GC-MS) analysis of EAE derived from S. carpaticus EGY-S7 strain was also identified.