Characterization of glycolipid biosurfactant from Pseudomonas aeruginosa PA 1 and its efficacy against Phytophtora infestans

ABSTRACT

Aim: The aim of the present study was to identify biosurfactant produced by Pseudomonas aeruginosa and to determine the effectiveness of biosurfactants (rhamnolipid) against P. infestans causing late blight of potato. Methodology: Pseudomonas aeruginosa strains were isolated from soil samples and the potential strain PA 1, selected because of its antagonistic ability, was used to optimize anti-metabolite production and its characterization using HPLC-Mass spectrometry. Rhamnolipid based formulation was developed and its efficacy was tested against late blight disease. Results: The results revealed that four rhamnolipids congeners were identified, among them three were mono-rhamno-di-lipidic congeners and one was di-rhamno-di-lipdic congeners, abundantly present in the crude biosurfactant obtained from P. aeruginosa PA1. The mass spectra of mono-rhamno-di-lipidic Rha-C12-C14 peak value (m/z 584), Rha-C12.1-C10.CH3 peak value (m/z 545), Rha-C12-C-12-CH3 peak value (m/z 575) and di-rhamno-di-lipidic. Rha-Rha-C10-C10 peak value (m/z 651) were also detected. Rhamnolipid-based formulation was developed and evaluated at different concentration ranging from 0.012 and 0.3% in detached leaf test. Significant reduction in lesion area was recorded at 0.2% concentration (lesion area 0.06 cm2 as against 9.8 cm2 on 5th day of inoculation). Interpretation: Microbial produced rhamnolipid based formulation at 0.2% concentration was found effective against late blight of potato in detached leaf test. Further, it could be used in field study as green chemical which would help in replacing application of chemicals in agriculture.