Wheat plant –Plant Growth Promoting Rhizobacteria (PGPR) interaction to alleviate the salt stress in vitro and in vivo

Abstract

The current work studied the mechanistic basis of salt tolerant PGPR bacteria in alleviating salinity stress in wheat.Two experiments were conducted at the Agricultural Research Center (ARC), 2021-2022, to evaluate the interaction between wheat var. Misr1 and two salt tolerant PGPR bacterial strains, Azospirillum (A.) brasilense NO40 and Bacillus thuringiensis (Bt) under saline conditions. The staining technique used to detect the colonization effectiveness of applied bacteria. Images of 30-day wheat seedlings were captured and subjected to the following measurements: root area, leaf area, root length, shoot length, and dark green color index (DGCI). TEM was used to look for bacterial colonization in wheat seedling. Chlorophyll, proline, peroxidase activity, rhizosphere dehydrogenase activity and electrical conductivity (EC) were all quantified. Results revealed that the wheat seedling roots inoculated with the salt tolerant bacterial strains produced a highly intense red colour. The colonized bacteria appeared on the outer surface of the root and intercellular space of root tissue. The data showed a significant rise in all measured parameters in the inoculated wheat seedlings with the salt tolerant bacterial strains compared to the non-inoculated wheat seedlings. Additionally, the wheat seedlings inoculated with a mixture of NO40 and Bt showed the best results as compared to that inoculated with only NO40 or with only Bt. Finally, EC values before and after planting with the inoculated wheat seeds revealed a decrease in the salinity of the soil rhizosphere (9.27 mmhos/cm vs. 5.1 mmhos/cm). In conclusion: Salt stress in wheat saline soils was alleviated by bacterial strains studied. Optimum results were obtained from the mixture of A. brasilense and Bt. Results must later be verified in field trials.