Major part of potassium in soil exists in form of insoluble K-minerals. Fraction of Ksolubilized from such minerals through potassium solubilizing bacteria (KSB) will reduce cost on import of K- fertilizers. Nine and four isolates of K-solubilizing bacteria from Inceptisol (KI) and Alfisol (KA), respectively were evaluated for their ability to release of K from waste mica at 7, 14 and 21 days of incubation in modified Aleksandrov medium containing powdered waste mica as sole source of potassium. Morphological characteristics, zone of solubilization at week end and acidity of broth at different incubation periods were also studied. Majority of the isolates were entire smooth margin, raised, translucent, gram +ve rods and whitish to creamy in appearance. Isolates from cereals caused more zone of solubilization than pulse isolates. Isolates either from Alfisol or from Inceptisol efficiently decreased pH of the broth with increase in incubation periods. Isolates of same soil type differed in their K-release capacity. KSB isolates from Inceptisol showed higher K solubilization potential than isolates from Alfisol. Isolate KI₁ & KA₁₉ caused maximum acidity but lowest release of K from mica indicated that decrease in pH of the medium is not the only mechanism of K release from native K mineral of soil. Isolate KI₁₆ and KA₅₉ were high slime producer and showed highest 23.88 and 13.71 μg mL⁻¹ K solubilization capacity, respectively and emerged out as potential isolates of Ksolubilizers as a K- biofertilizers.

The abiotic stresses like drought, heavy metal and salts directly or indirectly influence the global environmental pollution and decrease the agricultural productivity. The stress tolerant plant growth promoting rhizobacteria (PGPR) play an important role against the abiotic stresses in terms of enhancing the efficacy of soil, plant growth promotion (PGP). Stress tolerance PGPRs have certain specific PGP properties such as hormones synthesis, 1-aminocyclopropane-1-carboxylate (ACC) deaminase, Indole-3-acetic acid (IAA) production, Abscisic acid (ABA) synthesis, enzymes production, nitrogen fixation, phosphorus (P) and Potassium (K) solubilization, as results which protect various crops during such stress conditions and consequently enhance crop sustainability. Efficient PGPRs isolated from various stress conditions have certainly, more useful against that particular stress. This article highlighted the isolation of various stresses tolerant PGPRs from varieties of crops under different stress conditions and their effect on varieties of crops to enhance their plant growth promotion.

Plant Growth Promoting Rhizobacteria (PGPR) is a group of bacteria that has the ability to enhance plant growth and yield via various plant growth promoting substances as well as biofertilizers. Ten bacterial isolates screened from rhizosphere of maize growing at Indo-Gangetic plain of eastern Uttar Pradesh, India showed potential nutrients solubilization and plant growth promoting activities. Rhizobacterial were able to produce phytohormone auxin (IAA) in the tryptophan supplemented medium which showed maximum production by strain BHU8. Phosphate solubilization activity was highly observed in isolate BHU8 followed by BHU3, BHU9 and BHU10. Plant cell wall hydrolyzing enzymes (Cellulase and Pectinase) were expressed in BHU3, BHU8, BHU9 and BHU10 and among ten rhizobacterial strains only six strains (BHU1, BHU2, BHU3, BHU5, BHU8 and BHU10) produced siderophore. Based on 16S rDNA gene sequence strains BHU1, BHU2, BHU3, BHU8, BHU10 showed 99.6%, 99.8%, 99.8%, 99.7% and 99.9% sequence alignment respectively with Pseudomonas brassicacearum, Pseudomonas taiwanensis Pseudomonas aeruginosa, Pseudomonas saponiphila and Pseudomonas oryzihabitans, respectively whereas strains BHU4 and BHU5 showed 99.7% similarity with Rhizobium radiobacter and strains BHU6 and BHU9 showed 99.9% sequence aligned with Bacillus oceanisediminis and Bacillus flexus, respectively. Strain BHU7 exhibited 99.9% similarity with Enterobacter asburiae.