Evaluating the Potential of Rhizobacterial Isolates Enhancing Sorghum's Abiotic Stress Tolerance: A Focus on Ethiopian Soil Isolates From Sorghum Root

Abstract

Sorghum is an economically important crop for human consumption, animal feed and biomass production. However, its productivity is affected by abiotic and biotic stresses. Drought is one of the major global problems due to alarming global climate change. Plant growth-promoting rhizobacteria (PGPR) help crops improve their resilience and survival in water-scarce environments. Therefore, the present study aimed to investigate the growth-promoting potential of rhizobacterial isolates to improve sorghum tolerance to drought and other abiotic stress. The bacterial sample from different soil roots of sorghum genotype was isolated from different locations in Ethiopia using serial dilution techniques. The biochemical properties of these isolates were evaluated. The potential of these PGPR traits to improve abiotic tolerance in sorghum was analysed under different temperatures, pH, salinity and drought stress. Furthermore, the potential of the rhizobacterial isolates' performance to improve sorghum drought tolerance was evaluated using four different concentrations of PEG (6000): (10%, 15%, 25% and 32.6%), which induces osmotic stress by reducing water availability, thus mimicking the effects of drought in sorghum. PCR detection of genes associated with abiotic stress, such as phosphate solubilisation, nitrogen fixation, ACC (1-aminocyclopropane-1-carboxylate) deaminase and phytohormone production was performed using the designed primers. In addition, identification and molecular characterisation of PGPRs was performed using 16S ribosomal RNA (rRNA) gene-specific primers. Serial dilution techniques of soil from different sorghum genotype roots resulted in the identification of 210 rhizobacterial isolates. Biochemical analysis revealed that 68 isolates exhibited their potential for nitrogen fixation, while 50 isolates showed their ability to solubilise phosphate. PCR amplification identified genes involved in phosphate solubilisation, nitrogen fixation, ACC (1-aminocyclopropane-1-carboxylate) deaminase and phytohormone production in several rhizobacterial isolates, suggesting that they have the potential to improve sorghum abiotic stress tolerance. Among the 68 rhizobacterial isolates examined, PCR amplification identified the nifH gene in 16 isolates, the acdS gene in 10 isolates and the pgg gene in 21 isolates. Among these, the Pseudomonas ms22 bacterial isolate showed a high potential to promote sorghum growth under greenhouse performance. Therefore, our findings suggest that harnessing the potential of Pseudomonas ms22 could pave the way for environmentally friendly and efficient agricultural practices under abiotic stress conditions.