The Rhizobacterium Bacillus amyloliquefaciens MHR24 Has Biocontrol Ability Against Fungal Phytopathogens and Promotes Growth in Arabidopsis thaliana

A novel rhizobacteria <i>Bacillus</i> was isolated from rhizosphere of soil associated with tomato (<i>Solanum lycopersicum</i> L.) under open field conditions. The <i>Bacillus amyloliquefaciens</i> strain MHR24 (MHR24) is a promising biocontrol agent against several fungal phytopathogens. In this research, MHR24 was characterized by an effective antagonistic ability against <i>Alternaria alternata</i> (Aa), <i>Botrytis cinerea</i> (Bc), <i>Fusarium oxysporum</i> F1 (F1), <i>F. oxysporum</i> F2 (F2), <i>F. oxysporum</i> R3 (F3), and <i>Sclerotinia sclerotiorum</i> (Sc). In particular, MHR24 showed a strong inhibition via airborne volatiles against Bc, F3, Aa, and F2 fungal strains. MHR24 also showed elevated saline stress tolerance at 1% and 25% to NaCl and KCl. The molecular sequence analysis of 16S rDNA confirmed the identity of the isolate as <i>Bacillus amyloliquefaciens</i> strain MHR24. Bioassays on <i>Arabidopsis thaliana</i> Col-0 inoculated with MHR24 showed in in vitro conditions that MHR24 significantly increases the foliar and root area, while in growth chamber conditions, it strongly increases the dry shoot biomass of <i>A. thaliana</i>. The observed results indicate that <i>B. amyloliquefaciens</i> MHR24 has a broad-spectrum biocontrol against fungal phytopathogens and can be used as a biofertilizer and biocontrol agent to improve horticultural crops.