Streptomyces araujoniae HZ-R6, isolated from Himalayan onion ( Allium wallichii Kunth) endorhiza, promotes growth of Chinese chive and protects from grey mould caused by Botrytis cinerea

Chinese chive (Allium tuberosum Rottler ex Spreng.), a perennial herb originating from China, is gaining popularity due to its nutritional values and medicinal properties. Grey mould caused by Botrytis cinerea, inflicts substantial economic damage upon the Chinese chive industry. Streptomyces, a ubiquitous bacterial genus that can be associated with plants, is renowned for its remarkable capability to synthesise an array of bioactive compounds. These compounds have demonstrated significant value in the realm of agricultural applications. Nevertheless, studies emphasised the exploration of eco-friendly management approaches, such as biocontrol microorganisms and plant growth-promoting bacteria (PGPB) specifically for Chinese chive, still subject to restrictions to this day. In our study, 21 endophytic Streptomyces strains, identified by molecular methods and morphological analysis, were isolated from Himalayan onion (Allium wallichii Kunth) collected from Jiucaiping mountain, Guizhou, China. Among them, S. araujoniae HZ-R1, HZ-R3, HZ-R6, HZ-R10, and HZ-S2 illustrated strong antagonistic activity (≥50 per cent of mycelium growth inhibition) against Botrytis cinerea in vitro. Additionally, S. araujoniae HZ-R6 showed remarkable growth-promoting capabilities by directly increasing plant biomass and indirectly enhancing various physiological properties. Leveraging its potential as biostimulant, we assessed the efficacy of S. araujoniae HZ-R6 against B. cinerea on Chinese chives in a greenhouse setting. A statistically significant 43.28% reduction in disease incidence and disease index was observed in the treatment group compared to the control group. Our findings suggests that S. araujoniae HZ-R6 has great potential to be further considered as a biofertilizer or biofungicide for the production of Chinese chives.