Abstract
Pesticides are widely used in different parts of the world to control insect pests and to enhance crop production. However, these pesticides are found to have deleterious effects due to their non-degradable nature and residual effects on non-target organisms. Some microorganisms can develop resistance against these pesticides and use them as the carbon source. These microorganisms can successfully be used for bioremediation of pesticides contaminated sites in addition to their plant growth promoting attributes. Bifenthrin is the major pesticide used in vegetables especially okra, to control fruit borer. A study was conducted to isolate and characterize the pesticide-tolerant rhizobacteria from rhizosphere of okra (Abelmoschus esculentus L.). Total 20 bacterial strains were isolated from rhizosphere of okra plants where high dose of bifenthrin was applied. Pesticide tolerance of rhizobacterial strains was determined at three different levels (100, 250 and 500 mg L-1 ) of bifenthrin. The results revealed that bacterial strains showed a variable response to increasing levels of bifenthrin and the growth of most of these strains decreased with increase in pesticide dose. The strain S10 showed the highest growth at 500 mg L-1 of bifenthrin followed by S20 and S6. These isolates were further characterized for plant growth promoting traits, such as Zn solubilization, urease and catalase activities, ammonia production, salinity stress tolerance, and growth at different pH levels. Out of 20 isolates, S1, S6, S8, S10, S13, S14 and S20 showed Zn solubilization ability while S3, S9, S12, S13, S14, S15, S19 and S20 were positive for urease activity. The isolates S6, S8, S14 and S20 showed ammonia production ability. All tested isolates showed the presence of catalase enzyme. The maximum root colonization ability was observed by S20. At highest salinity level, maximum cell growth was observed in the case of S20. All the rhizobacterial isolates showed maximum optical density at neutral (7), followed by alkaline pH (9). In general, S10 and S20 were better isolates and had the maximum pesticide tolerance along with other multifarious traits. These isolates may be evaluated for their ability to degrade bifenthrin pesticide and may have practical application for bioremediation of pesticide contaminated sites.
Najam-ul-Sehar, Maqshoof Ahmad, Muhammad Fakhar-u-Zaman Akhtar, Moazzam Jamil, Muhammad Latif , Iqra Ahmad. (2015) Pesticide tolerant plant growth promoting rhizobacteria isolated from rhizosphere of okra, The Journal Soil & Environment , Volume 34, Issue 2.
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