| Summary: | Background: Natural plant extracts and microbial antagonists have the potential for use in increasing the fungal resistance and productivity of horticulture plants. Methods: The purpose of this study was to evaluate the ability of both natural plant extracts and microbial antagonists as a biotical control of some fungal pathogens, i.e., <i>Fusarium</i> ssp., <i>Exserohilum</i> ssp. and <i>Nigrospora</i> ssp., along with improving the growth and productivity performance of zucchini under greenhouse conditions. <i>Eucalyptus camaldulensis</i> leaf extract (LE), <i>Citrus sinensis</i> LE, <i>Ficus benghalensis</i> fruit extract (FE), and two microbial antagonists <i>Pseudomonas fluorescens</i> (accession no. MW647093) and <i>Trichoderma viride</i> (accession no. MW647090) were tested under in vitro and in vivo conditions. Through morphological characteristics and the internal transcribed spacer (ITS) region, <i>Fusarium solani</i> (accession no. MW947256), <i>F. oxysporum</i> (accession no. MW947254), <i>Exserohilum rostratum</i> (accession no. MW947255), and <i>Nigrospora</i> <i>lacticolonia</i> (accession no. MW947253) were identified. HPLC analysis was used for the identification of phenolic compounds (PCs) and flavonoid compounds (FCs) in the extracts. Results: The highest inhibition percentage of fungal growth (IPFG) against <i>F. oxysporum</i> was obtained with <i>P. fluorescens</i>, <i>T. viride</i>, and <i>E. camaldulensis</i> LE (4000 mg/L); <i>F. solani</i> with <i>P. fluorescens</i>, <i>T. viride</i>, and <i>C. sinensis</i> LE (4000 mg/L); <i>Exserohilum rostratum</i> with <i>P. fluorescens</i>, <i>Ficus benghalensis</i> FE (4000 mg/L) and <i>E. camaldulensis</i> LE (4000 mg/L), and <i>N. lacticolonia</i> with <i>P. fluorescens</i>. Using HPLC analysis, the abundant PCs in <i>E. camaldulensis</i> LE were pyrogallol, and caffeic acid, those in <i>C. sinensis</i> LE were syringic acid and ferulic acid, and those in <i>F. benghalensis</i> FE were gallic acid and syringic acid. In addition, the abundant FCs in <i>E. camaldulensis</i> LE were kaempferol, and naringin, those in <i>C. sinensis</i> LE were hesperidin and quercetin, and those in <i>F. benghalensis</i> FE were kaempferol and quercetin. Under greenhouse experiments, <i>T. viride</i> and <i>E. camaldulensis</i> LE (4000 mg/L) followed by <i>P. fluorescens</i> + <i>T. viride</i> treatments gave the best results of zucchini plants in terms of leaf area, fruits number per plant, yield per plant, and total yield (marketable and non-marketable). Conclusions: Plant extracts and bioagents can be used to control some zucchini fungal pathogens and increase the productivity performance of zucchini plants.
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