Analysis of biodegradation potential of plant growth promoting rhizobacterial strains Burkholderia sp and Serratia sp

Abstract

newline x newlineABSTRACT newlineLimited land for agriculture, increasing population and increases food demand has led to the extensive use of synthetic pesticides. No doubt, the use of these pesticides have greatly increased the crop productivity and yield by reducing the crop loss due to the pests and also have their role in prevention of vector borne diseases. But their extensive and repeated use and long half-lives resulted to their accumulation in the environment which ultimately have adverse effect on the various non-target species such as humans and beneficial soil microorganisms including plant growth promoting rhizobacteria. Here in this investigation, we have identified the PGPRs strains that can degrade the pesticides while playing role in plant growth promotion. newlineIn the present study, we aimed to explore the pesticide degradation potential of PGPR strains, B (Burkholderia)-AU4i and Sf (Serratia fonticola)-AUP(3)3. These strains, which were originally isolated from our lab, were found to grow in medium with pesticides (carbendazim and chlorpyrifos) supplemented at a very high concentration (4000 mg/l). Strain B-AU4i was found more efficient in the biodegradation of both the pesticides, carbendazim and chlorpyrifos, 95% and 85% degradation respectively within 48 h, whereas Sf-AUP(3)3 degrade upto 84% and 66% carbendazim and chlorpyrifos respectively. Both the rhizobacterial strains were further treated with different doses (higher than recommended dose) of fungicides and insecticides to investigate their effect on plant growth promoting activities. Between 1 to 10 mg/l concentration range of each fungicide and insecticide we have observed no or very less effect of pesticides over the various plant growth promoting activities of both the strains. Although at 100 mg/l concentration of pesticides, PGP activities got significantly reduced but still sufficient to promote plant growth. This statement was proved in our pea and gram seedling experiments in the presence of 100 mg/l concentration of chlorpyrifos. Use of chlorpyrifos-tolerant B-AU4i and Sf-AUP(3)3 as inoculant not only shielded the pea and gram seedlings from the phytotoxicity of chlorpyrifos but also increased the overall growth of gram and pea seedlings. Both the strains were also found to grow in the presence of various aromatic compounds such as toluene, phenol, naphthalene and biphenyl. Previously, the genome newlinexi newlinesequencing of B-AU4i was done in our lab and we found that B-AU4i indeed contains genes that could be responsible for conferring pesticides degradation. newlineThe results suggested that both the rhizobazterial strains, B-AU4i and Sf-AUP(3)3, exhibit excellent biodegradation and plant growth regulating physiological features and can be used as a bio-inoculant in pesticides contaminated soil to enhance the crop production and side by side to degrade pesticides. newlineKeywords: PGPR, Serratia fonticola, Burkholderia, Rhizosphere, Genomics, Pesticides