Abstract
Date palm (Phoenix dactylifera L.) is considered the main crop in deserts and arid areas such as Saudi Arabia. Five Streptomyces species and other fungal species were isolated from date palm rhizosphere soil of several cultivars, such as Barhi, Khalas, Sullaj, and Sukkari, in the Ghat and El-Gouf regions. Streptomyces strains were isolated on Biolog universal growth agar medium and were identified following Biolog methods. The predominant Streptomyces isolated from this present survey was S. plicatus followed by S. rimosus, S. rutgersensus, and S. griseus. The number of soilborne fungi in the tested soil decreased with the increased number of isolated Streptomyces. There was a significant positive correlation between the date palm cultivar and the number of isolated Streptomyces. The in vitro effects of isolated Streptomyces species on some toxigenic fungi were also studied. Enzyme-linked immunosorbent assay, immunoaffinity column chromatography, and high-performance liquid chromatography were used to study the mycotoxins. The concentration of most of the tested mycotoxins was reduced significantly with the presence of the Streptomyces isolates. Results indicate that some Streptomyces isolates established in date palm rhizosphere have the ability to reduce production of mycotoxins of some toxigenic fungi; thus they have the potential of reducing the subsequent disease occurrence. Therefore they can be applied in wider range as biocontrol agents.