Screening of Streptomyces Spp. As A Biocontrol Agents Against Downy Mildew (Peronospora Belbahrii) Infecting Basil (Ocimum Basilicum L.)

Peronospora belbahrii is the destructive pathogen that causes downy mildew, which significantly impacts basil cultivationglobally. Chemical control is an effective method to protect crops from downy mildew, but its application in basilcultivation is limited due to concerns about chemical residue at harvest. The present study aimed to screen differentStreptomyces isolates for their antagonistic activity against the downy mildew pathogen (Peronospora belbahrii) infectingbasil (Ocimum basilicum L.) under field conditions. Results show that some isolates significantly reduced disease incidence and severity of downy mildew in basil plants compared to untreated controls. Moreover, treated plants showed improved vegetative growth and increased chlorophyll content and higher activities of antioxidant enzymes (peroxidase, polyphenol oxidase, ascorbate peroxidase, and catalase). These findings suggest that certain Streptomyces spp. have promising potential as biocontrol agents and could be further explored for sustainable management of downy mildew disease in basil.