Growth promotion effects of Bacillus subtilis on Bletilla striata seedlings

Objective: The objective of the study is to study the growth promotion effects of Bacillus subtilis inoculants on the growth of Bletilla striata seedlings. Methods: Various concentrations (1/10×, 1/50×, 1/100×, and 1/500 × dilutions) of B. subtilis inoculants were applied on the B. striata seedlings. Plant height, base diameter, leaf length, leaf width, relative chlorophyll content, tuber diameter, average fibrous root length, number of fibrous roots, and fresh weight were measured after incubation for 50 days. Results: Treatments with different concentrations of B. subtilis significantly increased the number of fibrous roots of the B. striata seedlings and promoted root elongation, and a higher concentration (1/10 × dilution) is associated with more significant promotion effects. B. striata seedlings treated with different concentrations of B. subtilis all showed an increase of relative chlorophyll contents in leaves with the increasing inoculant concentration. Only B. subtilis inoculant at a high concentration (1/10 × dilution) significantly promoted the plant height and base diameter of B. striata seedlings. The application of B. subtilis did not significantly promote the tuber diameter and fresh weight of B. striata seedlings. Principal component analysis confirmed the maximum growth promotion by B. subtilis inoculant in 1/10 × dilution than the other treatments. Conclusions: The application of B. subtilis can increase the relative chlorophyll content, promote growth and development of roots, and increase plant height and base diameter of B. striata seedlings. Therefore, B. subtilis has significant growth promotion effects on B. striata seedlings. These findings provide theoretical basis for the ecological cultivation of B. striata.