Int.J.Curr.Microbiol.App.Sci (2019) 8(6): 2679-2688 2679 Original Research Article https://doi.org/10.20546/ijcmas.2019.806.322 Ultrastructural Studies to Establish the Mode of Action of Pseudomonas fluorescens against Aspergillus flavus using Scanning Electron Microscope M. Ravi Teja 1* , K. Vijay Krishna Kumar 2 and H. Sudini 3 1 College of Agriculture, Professor Jayashankar Telangana State Agricultural University (PJTSAU), Rajendranagar, Hyderabad-500030, Telanagana, India 2 Acharya N.G. Ranga Agricultural University, Guntur, Andhra Pradesh- 522034, India 3 International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), Patancheru, Telangana-502324, India *Corresponding author ABSTRACT Introduction In India groundnut is an important oil seed crop which is a rich source of protein, dietary fiber, minerals, and vitamins (Ntare et al., 2008). Among different biotic stresses in groundnut cultivation, aflatoxin contamination is an important one which occurs at both pre-andpost-harvest stages of the crop. These aflatoxins are produced by Aspergillus flavus and A. niger. It is a qualitative problem affecting grain quality andtrade (Waliyar et al., 2008). Several management strategies have been attempted to minimize the aflatoxinproblem, in which biological control is a viable option. Of International Journal of Current Microbiology and Applied Sciences ISSN: 2319-7706 Volume 8 Number 06 (2019) Journal homepage: http://www.ijcmas.com In Groundnut aflatoxin contamination is a major problem which affects the quality of the seed. These aflatoxins have carcinogenic, hepatotoxic, teratogenic and immuno- suppressive effects which were produced by Aspergillus flavus and A. parasiticus. For the management of aflatoxin problem in groundnut, use of plant growth-promoting rhizobacteria (PGPR) is a viable and sustainable option. Our present study is aimed at determining the mode of action of these PGPR ( Pseudomonas fluorescens) using Scanning Electron Microscope (SEM). A superior P. fluorescens isolate (Pf7) identified from our studies in dual culture studies and in vitro seed colonization assay (IVSC) was screened against toxigenic isolate of A. flavus (AFT5B). In SEM, Pf7 exhibited both antibiosis and hyperparasitism. In antibiosis, deformation and coiling of hyphae of test fungus was noticed. Further, the mycelium appeared thread like, wrinkled and flaccid. Conidiophores are twisted near the zone of inhibition. In hyperparasitism, a white slimy growth of bacterial cells was seen on mycelia of test fungus. Further, structural disintegration of conidiophores and conidia of A. flavus was noticed. Overall, our results suggested the efficacy of Pf7 in reducing A. flavus infection and aflatoxin contamination through hyperparasitism and antibiosis. Keywords Groundnut, Aflatoxins, Aspergillus flavus, Pseudomonas fluorescens, SEM, Antibiosis, Hyperparasitism Accepted: 20 May 2019 Available Online: 10 June 2019 Article Info