Successful colonization of roots and Plant growth promotion of sorghum (Sorghum bicolor L.) by seed treatment with Pseudomonas putida and Azotobacter chroococcum
Uzma Sultana, Suseelendra Desai* and Gopal Reddy
Research Scholar ICAR-Central Research Institute for Dryland Agriculture, Santoshnagar, Hyderabad 500059, India.
Professor Emeritus, Department of Microbiology, Osmania University, Hyderabad 500007, India.
Accepted 26 June, 2016.
Citation: Sultana U, Desai S, Reddy G (2016). Successful colonization of roots and Plant growth promotion of sorghum (Sorghum bicolor L.) by seed treatment with Pseudomonas putida and Azotobacter chroococcum. World Journal of Microbiology, 3(1): 043-049.
Copyright: © 2016 Sultana et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are cited.
Pseudomonas putida (P29) and Azotobacter chroococcum (Azb19) are the efficient promising strains selected from in vitro plant growth promoting studies. These two strains were tested for their ability to promote growth of sorghum and colonize sorghum roots. Seed bacterization with P29 and Azb19 resulted in increased plant height, shoot height, root volume, leaf area and total plant dry mass. Further, bacterial inoculation also significantly increased macro-and micro-nutrient uptake by sorghum plants. Using electroporation method, pure cultures of P29 and Azb19 were transformed with pHC 60 plasmid containing gfp gene. Transformants detected by colony PCR were used to study the colonization pattern on roots of sorghum. Confocal fluorescence scanning microscope (CLSM) was used to locate the inoculants on or inside roots. Root colonization in sorghum by P29 was internal whereas Azb19 was detected on root surface. GFP-tagged Pseudomonas was predominantly detected at the root differentiation zone. In case of Azb19 small aggregates of micro-colonies were observed on the surface of the roots. The efficient sorghum root colonization by these inoculants clearly demonstrated that the introduced strains could successfully inhabit the rhizosphere and thus resulting in increased nutrient uptake. Inoculation with P29 resulted in increased uptake of P (288.5%), K (179.1%), Fe (242.7%), and Zn (168.1%) as compared to Azb19 where the uptake of P, K, Fe, Mn, and Zn increased by 142.6%, 161.6%, 199.5%, and 121.9%, respectively. On the other hand, inoculation with Azb19 could enhance better uptake of N (163.6%) as compared to P29 (133.3%). The strains also differed in their mode of root colonization.
Key words: Root colonization, Pseudomonas, Azotobacter, GFP, PGPR, Sorghum, Confocal, laser scanning microscope