Harnessing Bacillus safensis as biofertilizer for sustainable drought alleviation in Brassica juncea L

Carrier-based biofertilizers, which involve the introduction of plant growth-promoting bacteria into agricultural industry waste materials, are gaining increasing attention due to their profoundly positive impacts on soil health. In current study, various carriers, including dry leaves, sugarcane husk (SCH), rice husk (RH), and a combination/Mixture (MIX) of all three, were employed to support the bacterial strain, Bacillus safensis (SCAL1). This strain was utilized as a bioinoculant in the production of carrier-based biofertilizers. This particular strain was sourced from the Environmental and Microbial Botany Lab at Quaid-i-Azam University in Islamabad. Bacillus safensis strain exhibited notable improvements, evident in a high rate of longevity and larger colony-forming units within the carriers, as confirmed by measurements taken after 21 days of incubation. The drought stress was induced using polyethylene glycol solutions with concentrations of 15% and 25% administrated 6 and 15 days after germination, respectively. Four distinct biofertilizer types were formulated in the study: DL + SCAL1, RH + SCAL1, SCH + SCAL1, and MIX + SCAL1. When applied to Brassica juncea L. plants, all of these biofertilizers demonstrated the ability to mitigate drought stress and enhance the quality of Brassica juncea L. The immobilization onto SCAL1 by using SCH showed the best result compared to the liquid inoculum as carrier materials improve stability and shelf life. Furthermore, our results affirmed that carrier-based biofertilizers improved biochemical and physiological attributes of plants during drought conditions, highlighting their importance as a valuable resource for mitigating drought stress in Brassica juncea L. The findings revealed that carrier-based biofertilizers are an excellent source of diverse phytohormones, which are pivotal in alleviating drought stress.