Pseudomonas sp. strain AKM-P6 enhances tolerance of sorghum seedlings to elevated temperatures

A thermotolerant strain AKM-P6 of Pseudomonas sp. possessing plant growth-promoting properties was isolated from rhizosphere of pigeon pea grown under semiarid conditions in India. The effect of inoculation with AKM-P6 on survival and growth of sorghum seedlings at elevated temperatures (ET) was investigated under sterile and nonsterile soil conditions. Inoculation with strain AKM-P6 helped sorghum (var CSV-15) seedlings to survive and to grow at elevated temperatures (47–50°C day/30–33°C night) up to 15 days while uninoculated plants died by the fifth day of exposure to elevated temperature. Under sterile and nonsterile conditions, significantly higher root and shoot biomass were recorded in inoculated seedlings as compared to uninoculated control at ET, but this difference was nonsignificant at ambient temperature. Inoculation induced the biosynthesis of high-molecular weight proteins in leaves under elevated temperature, reduced membrane injury, and improved the levels of cellular metabolites like proline, chlorophyll, sugars, amino acids, and proteins. Scanning electron microscopy studies confirmed the colonization and establishment of the organism on the root surface. The 16SrDNA sequence of the strain AMK-P6 showed 97% homology with that of Pseudomonas aeruginosa in the existing database. The results indicate that Pseudomonas sp. strain AKM-P6 can enhance tolerance of sorghum seedlings to elevated temperatures by inducing physiological and biochemical changes in the plant.