Isolation of actinobacterial endophytes from wheat sprouts as biocontrol agents to control seed pathogenic fungi

Seed-borne Streptomyces can transmit vertically from generation to generation and be a mutualism between the endosymbionts and hosts. The aim of this study was to isolate and characterize endophytic Streptomyces strains from wheat sprouts, and to investigate their protection against wheat seed pathogenic fungi Penicillium. Endophytic Streptomyces sp. F6 and Streptomyces sp. F39 were isolated from wheat sprouts germinated under sterile conditions. Both Streptomyces strains could produce siderophores, and showed antagonistic activities against the seed pathogenic fungi Penicillium sp. Z17. The inoculation of Streptomyces sp. F39 and F6 could protect wheat seed germination and promote seedling growth under Penicillium sp. Z17 infection. However, the protection efficiency was impacted by the Streptomyces spore concentrations, the concentration ratios of Streptomyces spores to pathogen spores, and inoculation methods. The results suggested that wheat sprouts harbored diverse endophytic Streptomyces species which derived from wheat seeds, these strains should be more likely transmitted to the next generation, and confer competitive ability to pathogens on the offspring. Owing to the more intimate correlation between sprout endophytic flora with host plants, these strains are more suitable for mature plant interiors compared with those from rhizosphere soils and root interiors.