Unraveling the new member Bacillus pumilus SH-9 of Bacillaceae family and its potential role in seed biopriming to mitigate drought stress in Oryza sativa

Abstract

Rice is an important cereal crop cultivated worldwide to meet the need of hungry populations. Drought stress is a major problem that reduces crop productivity by up to 50 %. Beneficial microbes have the potential to mitigate drought stress in various crops. The use of beneficial microorganisms in seed biopriming techniques enhances germination potential through the production of antioxidants and phytohormones. In this study, the novel bacterial strain SH-9 was isolated and screened for various biological and stress tolerance assays. SH-9 exhibited plant growth-promoting characteristics such as abscisic acid production (2.18 ± 0.05 ng/ml), phosphate solubilization index (4.69 ± 0.30), and sucrose production (0.72 ± 0.05 mg/ml). The oxidative stress tolerance assay also revealed remarkable production of the antioxidant molecules catalase, superoxide dismutase, and ascorbate peroxidase. Germination metrics were also measured through seed biopriming in the experimental plant (Oryza sativa) treated with SH-9. Surprisingly, SH-9 was found to be significantly drought-tolerant as it could tolerate drought up to 35 % PEG 6000. Seed biopriming enhanced the germination potential by up to 90 % and improved the seed vigor index, germination energy, and germination rate index. It also improved the seedling characteristics of rice compared with the control group. This study demonstrated that SH-9 has excellent potential to enhance the germination metrics even under stress. Molecular identification revealed that SH-9 is a new member of the Bacillaceae family with the gene accession number ON753949. Overall, it is expected that further research on seed biopriming employing SH-9 strain in plants will lead to this technique being employed as a form of sustainable management in agriculture.