Potassium Solubilizing Rhizobacteria and Their Effect on Root Colonization of Wheat Plant

Nitrogen, phosphorus and potassium are known to be essential elements for plant growth. Thorough farming practices high yield require chemical fertilizers, which are not only expensive but may also produce environmental problems. The present study presenting the isolation and identification of rhizosphere bacteria with nitrogen fixing bacteria (NFB), phosphate solubilizing bacteria (PSB) and Potassium Solubilizing Bacteria (KSB) capacities from six different region in Egypt. A total of fifty two bacterial strains were isolated, characterized and classified to twenty two NFB, eighteen PSB and twelve KSB. Free NFB were tested for nitrogenase activity, the active NFB isolate 1N exhibited higher nitrogenase activity (330.2 n moles C H /ml/h) followed by isolates no. 7N recording 209.6 nmoles C H /ml /h. Qualitative and quantitative 2 4 2 4 methods were used to evaluate the phosphate and potassium solubilization effectiveness of the isolates. Results indicated that isolate no. 2P gave a large clear zone followed by isolates 12P. All of the eighteen PSB exhibited difference in their qualitative and quantitative efficiency to solubilize phosphate ranged from 65.9 to 220.2 % qualitatively; isolate no. 2P recorded 26.89 μg / ml after 14 days from incubation period, a slow decline in pH of medium was also observed from initial value of 6.21 to 5.10. All KSB isolates were able to K-solubilization mica supplemented to media as a sole source of K and formed variation of clear zones on Aleksandrow’s agar media in vitro. Isolate no. K5 gave large clear zone, solubilizing efficiency ranged from 50.44 to 230.11%. The amount of K is increased with increasing the incubation period 4-5 days at 35°C. Isolate no. 5K gave highest amount of K recorded 54.14 μg/ml and pH decreased through incubation periods. The top isolates strains from NFB, PSB and KSB (1N, 2P and 5K) were identified using 16S rDNA gene sequence analyses. The similarity sequence analysis indicated that no. 1N, no. 2P and no. 5K isolates have 99% similar sequence identify to Paenibacillus polymyxa, Bacillus nakamurai and Bacillus pacificus respectively. The colonization pattern of those strains were characterized using wheat plants on pots experiments. Overall the results indicates that the effect of NPK bacteria for enhancing the growth and increased the Vigor index recorded 70.83. Providing a great potential of using NPK bacteria for sustainable growth of wheat plants.