Background The study amid to investigate the influence of Trichoderma album, T. harzianum, T. koningii, Bacillus subtilis (EF1) and Pseudomonas fluorescens against Fusarium solani, the causal agent of root rot in squash under in vitro conditions. Field experiment was conducted to evaluate the effects of arbuscular mycorrhizal fungi i.e., (Glomus intraradices, G. monosporum, G. etunicatu, AMF) and T. harzianum (TZ) as well as B. subtilis (BS) either as individual or combined treatment against Fusarium root rot of squash in two successive seasons of study 2020 and 2021 using New Eskandrani cultivar. Results Trichoderma harzianum caused the greatest reduction in mycelial growth of F. solani (75.17%), followed by T. album and T. koningii. Amongst the tested 4 cultivars (Sakata, Galaxy, New Eskandrani H1 hybird, Hollr Queen F1 hybrid) in glasshouse, Hollr Queen was the most resistant to the infection of F. solani with survival rate (84.92%), whereas New Eskandrani c.v was the most susceptible. Results of filed experiments proved that the combined inoculation of AMF + TZ + BS, AMF + BS, AMF + TZ, TZ + BS resulted in significant elevation of total chlorophyll, carotenoids, free phenolic compounds, free amino acids, total protein as well as the antioxidative enzyme activities (i.e. Superoxide dismutase, Peroxidase and Polyphenol-oxidase) and contents of macro and micro elements. Results further showed that the combined treatments caused a significant decrease in disease severity in both seasons with subsequent significant increase of plant growth parameters as well as total fruit yield/plant and total fruit yield/feddan. Conclusion It could be concluded that the combined inoculations of the tested bioagents proved to have potentials in control of Fusarium root rot but large scale field experiments should be conducted before any ultimate conclusion or recommendation was drawn.

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