Halotolerant plant growth-promoting rhizobacteria-mediated alleviation of salinity and dust stress and improvement of forage yield in the desert halophyte Seidlitzia rosmarinus

In desert areas, a set of environmental stresses such as salinity and dust simultaneously affect plant biomass and nutritional value. In this study, the effects of two halotolerant plant growth-promoting rhizobacterial strains, Bacillus pumilus HR, isolated from the halophyte Halostachys belangeriana, and Zhihengliuella halotolerans SB, isolated from the halophyte Seidlitzia rosmarinus, on morpho-physiological, biochemical and ionomic properties of S. rosmarinus under salinity stress (0, 300, and 600 mM NaCl) and mineral dust (0 and 1.5 g m⁻² month⁻¹) were examined. Salinity stress reduced the morpho-physiological characteristics of S. rosmarinus plant more than dust stress. The dust application, similar to salinity stress, increased the content of Na, malondialdehyde (MDA), acidity, and glycine betaine in S. rosmarinus leaves. Z. halotolerans SB strain was more effective than B. pumilus HR strain in improving the characteristics of S. rosmarinus under salinity and dust stress. Under the conditions of combined application of salinity (at 600 mM NaCl level) and dust stress, this strain (SB) increased chlorophyll a content by 40%, protein content by 48%, Fe content by 45%, Mg content by 63%, Mn content by 21%, total dry biomass by 35%, seedling quality index by 104%, catalase activity by 47%, anthocyanin content by 85, and Na content by 53% in S. rosmarinus plant leaves compared to control. In addition, the results of PCA analysis showed that at salinity level of 300 and 600 mM NaCl, there were an increase in antioxidant indices and a sharp increase in Na and MDA content in S. rosmarinus leaves, respectively. It was also suggested that the bacterial strain (Z. halotolerans SB) can increase the quantity and quality of forage (seedling quality index) better than another bacterial strain (B. pumilus HR) under salinity and dust conditions. In general, the study reveals that the application of halotolerant rhizobacteria can be a cost effective and ecological sustainable method to improve the yield and quality of forage in the desert halophyte S. rosmarinus under salinity and dust stress conditions.