Effects of the IAA-Producing Endophytic Bacillus spp. on the Growth of Hordeum vulgare L.

Endophytic bacteria are beneficial microbes that live within plant tissues and promote growth through nitrogen fixation, phosphate solubilization, and phytohormone production. Two endophytic isolates from bell pepper (Capsicum annuum L.) root were identified based on their morphology and biochemical properties using 16S rRNA gene sequencing. Winter barley seeds were inoculated with two PGP (plant growth-promoting) bacterial strains (C-14 and C-27), previously characterized for indole-derived compound (IDC) production, and evaluated in a pot experiment with four treatments: Treatment A1 (C-14), Treatment A2 (C-27), Treatment A3 Consortium (C-14 + C-27), and Treatment A4 (non-inoculated control). The results indicated that root and stem lengths increased in plants inoculated with bacteria compared to the uninoculated control. Among treatments, A2 produced the greatest root and shoot lengths (17.23 and 26.2 cm), while A3 showed the lowest (15.8 and 21.5 cm). SPAD values also increased by 6%, 10%, and 3.2% in Treatments A1, A2, and A3, respectively. This study clearly demonstrated that the endophytic isolates (C-14 and C-27) obtained from bell pepper roots significantly enhanced the growth of barley due to their ability of IDC production, thereby offering a promising alternate to chemical fertilizers.