title: Pretreatment of Cr(VI)-amended soil with chromate-reducing rhizobacteria decreases plant toxicity and increases the yield of Pisum sativum.
abstract: Pot culture experiments were performed under controlled greenhouse conditions to investigate whether four Cr(VI)-reducing bacterial strains (SUCR44, SUCR140, SUCR186, and SUCR188) were able to decrease Cr toxicity to Pisum sativum plants in artificially Cr(VI)-contaminated soil. The effect of pretreatment of soil with chromate-reducing bacteria on plant growth, chromate uptake, bioaccumulation, nodulation, and population of Rhizobium was found to be directly influenced by the time interval between bacterial treatment and seed sowing. Pretreatment of soil with SUCR140 (Microbacterium sp.) 15 days before sowing (T+15) showed a maximum increase in growth and biomass in terms of root length (93 %), plant height (94 %), dry root biomass (99 %), and dry shoot biomass (99 %). Coinoculation of Rhizobium with SUCR140 further improved the aforementioned parameter. Compared with the control, coinoculation of SUCR140+R showed a 117, 116, 136, and 128 % increase, respectively, in root length, plant height, dry root biomass, and dry shoot biomass. The bioavailability of Cr(VI) decreased significantly in soil (61 %) and in uptake (36 %) in SUCR140-treated plants; the effects of Rhizobium, however, either alone or in the presence of SUCR140, were not significant. The populations of Rhizobium (126 %) in soil and nodulation (146 %) in P. sativum improved in the presence of SUCR140 resulting in greater nitrogen (54 %) concentration in the plants. This study shows the usefulness of efficient Cr(VI)-reducing bacterial strain SUCR140 in improving yields probably through decreased Cr toxicity and improved symbiotic relationship of the plants with Rhizobium. Further decrease in the translocation of Cr(VI) through improved nodulation by Rhizobium in the presence of efficient Cr-reducing bacterial strains could also decrease the accumulation of Cr in shoots.
authors.affiliation: Department of Microbial Technology, CSIR-Central Institute of Medicinal and Aromatic Plants, P.O. CIMAP, Lucknow, 226015, Uttar Pradesh, India.
authors.forename: Sumit K
authors.initials: SK
authors.lastname: Soni
authors.forename: Rakshapal
authors.initials: R
authors.lastname: Singh
authors.forename: Mangal
authors.initials: M
authors.lastname: Singh
authors.forename: Ashutosh
authors.initials: A
authors.lastname: Awasthi
authors.forename: Kundan
authors.initials: K
authors.lastname: Wasnik
authors.forename: Alok
authors.initials: A
authors.lastname: Kalra
mesh_terms: D001673:Biodegradation, Environmental; D002840:Chromates / Q000378:metabolism; D002857:Chromium / Q000032:analysis / Q000378:metabolism* / Q000633:toxicity; D052918:Environmental Restoration and Remediation / Q000379:methods*; D018532:Pisum sativum / Q000187:drug effects / Q000382:microbiology / Q000502:physiology*; D012230:Rhizobiaceae / Q000502:physiology*; D058441:Rhizosphere; D012987:Soil / Q000737:chemistry; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000032:analysis / Q000378:metabolism* / Q000633:toxicity
chemical_list: D002840:Chromates; D012987:Soil; D012989:Soil Pollutants; D002857:Chromium; C074702:chromium hexavalent ion