Twelve psychrotolerant Pseudomonad strains were selected on the basis of various plant growth-promoting (PGP) activities at cold temperature (4°C). The effect of inoculation with Pseudomonad strains on cold alleviation and growth of wheat seedling at cold temperature (8°C) was investigated under greenhouse condition. Inoculation with Pseudomonad strains significantly enhanced root/shoot biomass and nutrients uptake as compared to non-bacterized control at 60 days of plant growth. Bacterization significantly improved the level of cellular metabolites like chlorophyll, anthocyanin, free proline, total phenolics, starch content, physiologically available iron, proteins, and amino acids that are sign of alleviation of cold stress in wheat plants. Increased relative water content, reduced membrane injury (electrolyte leakage), and Na(+)/K(+) ratio were also recorded in bacterized wheat plants. Electrolyte leakage and Na(+)/K(+) were found inversely proportional to plant growth at cold temperature. Statistical analysis of twenty-three measured parameters revealed that uninoculated control was under cold stress while eight bacterial strains were positively alleviating cold stress in wheat plants. Thus, the psychrotrophic Pseudomonad strains could effectively provide a promising solution to overcome cold stress, which is major factor hindering wheat productivity under cold climatic condition.

A psychrotolerant, Gram negative, rod shaped, plant growth promoting bacterium (PGPB) was isolated from high altitude of North Western Indian Himalayas. The identity of the bacterium was confirmed by morphological, biochemical and sequencing of the 16S rRNA gene. The sequence analysis revealed maximum similarity with Pseudomonas vancouverensis. It exhibited tolerance to a wide pH range (5-12; optimum 7.0) and salt concentrations up to 5% (w/v). The isolate produced 8.33 and 1.38 g/ml of IAA at 15 °C and 4 °C respectively, on the third day after incubation. It solubilised 42.3, 66.3 and 74.1 g/ml of tricalcium phosphate at 4, 15 and 28 °C respectively after seven days of incubation. The strain also possessed HCN and siderophore production abilities at 4 °C. It exhibited inhibitory activity against several phytopathogenic fungi in three different bioassays. The maximum relative growth inhibition was recorded against Sclerotium rolfsii and Rhizoctonia solani (100%), followed by Pythium sp. (73.1%) and Fusarium oxysporum (19.7%), in volatile compound assays. Seed bacterization with the isolate enhanced the germination of wheat seedlings grown at 18 ± 1 °C by 20.3%. Bacterized seeds also recorded 30.2 and 27.5% higher root and shoot length respectively, compared to uninoculated controls.

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