Biocontrol of Fusarium culmorum and enhanced wheat seedling growth by Streptomyces sp. D15 from Algerian steppe soil: performance and genome analysis.

Wheat (Triticum aestivum L.), a staple crop in Algeria and other semi-arid regions, faces significant challenges from fungal pathogens like Fusarium culmorum, which cause substantial yield losses and threaten food security. This study investigates the biocontrol and plant growth-promoting potential of Streptomyces sp. D15, an actinobacterial strain isolated from steppe soil in Algeria. Phylogenomic analysis confirmed the classification of strain D15 as Streptomyces lavendofoliae. During in planta experiments on wheat seedlings, strain D15 improved shoot length with increases of 67% relative to control and 120% relative to FC-infested seedlings. Results revealed the strain's ability to significantly reduce the severity of F. culmorum-induced seedling blight, achieving 91% reduction in disease incidence and 87% reduction in disease severity. Additionally, D15 enhanced wheat emergence rate (143% improvement) and increased root lateral branching by 391% compared to infested seedlings. Genome annotation identified a diverse range of genes linked to biocontrol mechanisms, including chitinolytic enzymes, siderophore production, and antifungal secondary metabolites such as hydrogen cyanide. Moreover, genes related to phosphate solubilization and phytohormone biosynthesis, including indole-3-acetic acid and gibberellic acid, were detected, explaining the observed plant growth-promoting effects. This comprehensive investigation highlights Streptomyces sp. D15 as a promising biocontrol agent and growth promoter, offering an eco-friendly and sustainable alternative to chemical pesticides. Its remarkable adaptability to semi-arid environments and its potential for agricultural applications position it as a valuable tool for enhancing wheat productivity and resilience in regions facing both biotic and abiotic stressors.