Symbiotic nitrogen fixation (SNF) of transgenic grain legumes might be influenced either by the site of transgene integration into the host genome or due to constitutive expression of transgenes and antibiotic-resistant marker genes. The present investigation confirmed proper nodulation of five tested Bt-chickpea events (IPCa2, IPCa4, IPCT3, IPCT10, and IPCT13) by native Mesorhizobium under field environment. Quantitative variations for nodulation traits among Bt-chickpea were determined and IPCT3 was found superior for nodule number and nodule biomass. Diversity, as well as richness indices, confirmed the changes in bacterial community structure of root and root-nodules from Bt-chickpea events IPCa2 and IPCT10. Especially, Gram-positive bacteria belonging to Firmicutes and Actinobacteria were selectively eliminated from root colonization of IPCa2. Richness indices (CHAO1 and ACE) of the root-associated bacterial community of IPCa2 was 13-14 times lesser than that of parent cv DCP92-3. Root nodule associated bacterial community of IPCT10 was unique with high diversity and richness, similar to the roots of non-Bt and Bt-chickpea. It indicated that the root nodules of IPCT10 might have lost their peculiar characteristics and recorded poor colonization of Mesorhizobium with a low relative abundance of 0.27. The impact of Bt-transgene on bacterial community structure and nodulation traits should be analyzed across the years and locations to understand and stabilize symbiotic efficiency for ecosystem sustainability.

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Background and Objective : The current study reveals the effect of Aluminum (Al) on Amaranthus tricolor L andsubsequent biochemical changes on the plant. In this study, the effect of Al stress on growth and other related antioxidants andenzymes were investigated. Methodology : This was achieved by investigating plant growth parameters (root/shoot length, dryweight) in presence and absence of various concentrations of Al. The antioxidant activity was determined by estimating proline,ascorbate. The effects of scavenging enzymes were determined by Catalase, Glutathion and SOD activity. The accumulation ofAl in root and shoot was determined by FAAS (Flame Atomic Absorption Spectroscopy). Results: Al induced growthretardation observed more in roots (52.2%) compared to shoots (35.3%). Total concentration of proline increased (18 folds)compared to the control. The antioxidants and enzymes exhibited initial increase and subsequent decrease in response to Alstress. Accumulation of Al (by FAAS) was predominantly in root (70.44ppm ± 0.420).Conclusion: Result thus suggested Alinduced growth inhibition in Amaranthus tricolor and the primary affected region is the root. Al accumulation in the roots couldplay an important role in the acclimation of the genotype to Al stress, and could be used as physiological markers for Al-tolerance. Metal induced scavenging mechanism observed both at enzymatic and antioxidant molecular level.