Drought-Alleviating Effects of Endophytic Bacteria Isolated from Xerophytic Plants on Capsicum annuum L. Seedlings

In the current study, 51 endophytic bacteria were isolated from 5 different xerophytic plants. Their drought tolerance properties were screened in vitro, and from these, four endophytes with tolerance up to - 1.5 MPa water potential were further selected and identified as Acinetobacter sp. Eo3, Pseudomonas sp. Ni5, Bacillus safensis Ni7, and Stenotrophomonas sp. C3. Due to biosafety concern, Acinetobacter sp. Eo3 and Pseudomonas sp. Ni5 were excluded from further investigation, while B. safensis Ni7 and Stenotrophomonas sp. C3 were subjected to detailed study. The drought tolerance properties of these endophytes were evaluated in vivo using Capsicum annuum L. by analysing the growth parameters (leaf number, root number, shoot length, and plant fresh weight) as well as physiological and biochemical parameters (stomatal index, relative water content, chlorophyll content, and carbohydrate accumulation) of bacteria-treated and control seedlings. Here, treatment with B. safensis Ni7 and Stenotrophomonas sp. C3 was found to result in statistically significant enhancement (P <= 0.001) of the measured parameters of plants when compared with the control groups. In the case of fresh weight itself, Ni7 and C3 treatment was found to result in values of 157.76 and 142.8 mg, respectively, and was statistically significant enhancement as the same for nutrient broth and distilled water control were 73.3 mg and 70.5 mg only. Additionally, the endophyte-treated seedlings displayed significant improvement in other growth parameters even under induced drought stress. These findings highlight the potential of xerophytic-derived bacterial endophytes to have significant role in mitigating the drought stress effects in plants with the promises for field application.