Bacillus halotolerans DGL6 from the rhizosphere of Nitraria tangutorum in arid sandy land promotes growth and controls diseases of Triticum aestivum ‘Qingmai 7’

Abstract:

[Background] The extreme eco-environment of Qinghai Plateau harbors unique microbial resources. [Objective] To explore the growth-promoting and disease-controlling effects of Bacillus adaptive to the alpine environment on the herbage. [Methods] The growth-promoting and disease-controlling effects of Bacillus halotolerans DGL6 isolated from the rhizosphere of Nitraria tangutorum in Haixi prefecture of Qinghai province on the germination and seedling growth of Triticum aestivum ‘Qingmai 7’ were determined by seed soaking and root irrigation methods, respectively. The changes in physiological indexes of the seedlings within 12 days were measured. The inhibitory activity of strain DGL6 on fungal infection was measured with the detached leaves of ‘Qingmai 7’ seedlings. The inhibition rate and hydrolase activity of strain DGL6 against pathogenic fungi were determined by plate confrontation method and inhibition zone method, respectively. [Results] Strain DGL6 had significant effect on the seed germination and seedling growth of ‘Qingmai 7’. It increased the sprout length, root length, and fresh weight of ‘Qingmai 7’ by 27.26%, 23.03%, and 45.42%, respectively. Furthermore, it increased the plant height, root length, and fresh weight of seedlings within 12 days by 33.42%, 107.85%, and 95.24%, respectively. The strain significantly increased the content of chlorophyll, soluble sugar, and soluble protein and decreased the content of malondialdehyde. Spraying DGL6 suspension significantly inhibited the growth of Fusarium graminearum on the detached leaves of ‘Qingmai 7’. DGL6 showed significant antagonistic activity to F. graminearum, with the mean inhibition zone diameter of 18 mm. DGL6 formed distinct inhibition zones in the media for detection of four hydrolases, demonstrating the ability to secrete cellulase, pectinase, protease, and b-1,3-glucanase. [Conclusion] This study provided an elite strain and a theoretical basis for promoting the growth and improving the disease resistance of the plateau crop ‘Qingmai 7’.