• Nofet Margolis, 
• Dikla Eckstien, 
• Nadav Oren, 
• Omer Murik 
• Hagai Raanan 

Soil-borne pathogens cause severe diseases in many crops around the world. Due to the harmful nature of the chemical pesticides used against such pathogens, extensive research has focused on developing sustainable solutions such as biocontrol agents. Nevertheless, the complex interaction of such agents with their biotic and abiotic environment is challenging. Filamentous cyanobacteria, the pioneers and main primary producers in biological soil crusts (BSC), show considerable tolerance to extreme environmental conditions within the crust. Soil inoculation with cyanobacteria is a promising practice for sustainable agriculture in drylands where high tolerant organisms is required. Nevertheless, its plant protection potential has been less explored. Cyanobacteria such as Leptolyngbya ohadii, a dominant species in the BSC of the northwest Negev desert, Israel, are known to produce a large array of secondary metabolites. Application of L.ohadii spent media severely inhibits the growth of various prokaryotes and eukaryotes. Its resilience and the observed antimicrobial activity thus make L.ohadii a promising candidate for the development of a biocontrol agent. However, little is known about the effect of environmental conditions on its antimicrobial activity. Here we examined the antifungal activity of L.ohadii on a range of soil-borne fungal pathogens. We assessed the effect of the daily hydration/dehydration cycle of its natural habitat on the expression of gene clusters for secondary metabolites production using a novel custom-made environmental conditions simulation chamber. Our data advance the understanding of the complex interaction of L.ohadii with its biotic and abiotic environment for application as a dryland biocontrol agent.