The effect of growth-promoting bacteria on yield and some biochemical characteristics of black cumin (Nigella sativa L.) under drought stress conditions

An approach to overcome drought stress is using growth-promoting bacteria. This study was carried out to investigate the effect of Azospirillum growth-promoting bacteria under drought stress on yield and biochemical characteristics of Nigella sativa L. in the crop year 2019-2020 in Servak village of Yasouj province in Kohgiluyeh and Boyer-Ahmad province. The experiment was performed as a factorial split plot in a randomized complete block design with three replications. The main factor was irrigation in three levels (irrigation after using 30% soil moisture (control), irrigation after using 60% soil moisture, and irrigation after using 90% soil moisture) and the sub-factor of Azospirillum growth-promoting bacteria in two levels (no inoculation and inoculation of seeds with bacteria). Results showed that inoculation of growth-promoting bacteria increased yield and carbohydrate under moderate stress conditions. In high stress conditions, carotenoid and malondialdehyde had significant changes. Chlorophyll a, chlorophyll b, total chlorophyll, and carotenoids had significant changes under both moderate and severe stress. On the other hand, chlorophyll a, chlorophyll b, total chlorophyll, and carotenoids had significant changes in both moderate and high stress. The highest concentrations of total chlorophyll (1.01 mg / g fresh weight) and carotenoids (0.77 mg / g fresh weight) were observed in irrigation after consuming 30% soil moisture and inoculation with bacteria. The highest yield (1072 kg / ha) was observed under consuming 30% soil moisture and bacteria. Measuring the rate of plant growth is suggested at different stages to determine the effect of stress in each period to get a perfect interpretation of the effect of stress on the plant.