Bacterial Community Structure in the Rhizosphere of a Cry1Ac Bt-Brinjal Crop and Comparison to Its Non-transgenic Counterpart in the Tropical Soil

Abstract

To elucidate whether the transgenic crop alters the rhizospheric bacterial community structure, a 2-year study was performed with Cry1Ac gene-inserted brinjal crop (Bt) and their near isogenic non-transformed trait (non-Bt). The event of Bt crop (VRBT-8) was screened using an insect bioassay and enzyme-linked immunosorbent assay. Soil moisture, NH4 (+)-N, NO3 (-)-N, and PO4 (-)-P level had non-significant variation. Quantitative polymerase chain reaction revealed that abundance of bacterial 16S rRNA gene copies were lower in soils associated with Bt brinjal. Microbial biomass carbon (MBC) showed slight reduction in Bt brinjal soils. Higher MBC values in the non-Bt crop soil may be attributed to increased root activity and availability of readily metabolizable carbon compounds. The restriction fragment length polymorphism of PCR-amplified rRNA gene fragments detected 13 different bacterial groups with the exclusive presence of β-Proteobacteria, Chloroflexus, Planctomycetes, and Fusobacteria in non-Bt, and Cyanobacteria and Bacteroidetes in Bt soils, respectively, reflecting minor changes in the community structure. Despite the detection of Cry1Ac protein in the rhizospheric soil, the overall impact of Cry1Ac expressing Bt brinjal was less compared to that due to seasonal changes.

Effects of Bt-cotton on biological properties of Vertisols in central India

“…reported that soil MBC was inhibited by transgenic cotton proteins compared to their non-transgenic controls. Similarly, Singh et al (2013b) reported that MBC was slightly reduced in the transgenic brinjal soils, and the overall impact of transgenic brinjal was lower than nontransgenic brinjal due to seasonal changes (Singh et al 2013b). Contrarily, higher amounts of MBC under various Bt-cotton and bulk soils were found in Indian Vertisols than non-Bt cotton soils (Velmourougane & Sahu 2013).…”

Cry1Ac Transgenic Sugarcane Does Not Affect the Diversity of Microbial Communities and Has No Significant Effect on Enzyme Activities in Rhizosphere Soil within One Crop Season

“…Considerable previous work has been done in terms of biosafety on the soil enzyme and/or microbial community structure of cry1Ac transgene crops, including cry1Ac transgenic cotton (Shen et al, 2006 ; Zhang et al, 2015 ), cry1Ac transgenic brinjal (Singh et al, 2013 ), and cry1Ac transgenic oilseed rape (Liu et al, 2015 ). Shen et al ( 2006 ) investigated the potential risk of transgenes on the soil ecosystem of cry1Ac cotton (Sukang-103) and its non- cry1Ac cotton counterpart (Sumian-12) and found that there was no evidence for any adverse effect of cry1Ac cotton on the soil ecosystem.…”

“…Zhang et al ( 2015 ) found that cry1Ac cotton did not show any clear effects on soil microbial communities but the microbial communities were markedly affected by the plant growth stage. Singh et al ( 2013 ) evaluated the rhizospheric bacterial community structure of cry1Ac brinjal and their near isogenic non-transformed trait and found that microbial biomass carbon showed a slight reduction in cry1Ac brinjal soils and the overall impact of c ry1Ac expressing transgenic brinjal was lower than that due to seasonal changes. Liu et al ( 2015 ) assessed the impacts of cry1Ac transgenic oilseed rape on soil nematodes and microbial communities and concluded that there was no direct effects on the rhizosphere nematode and microbial communities.…”

Rhizospheric fungal community structure of aBtbrinjal and a near isogenic variety

“…Singh et al . (,c) have recently assessed the variation in actinomycetes and bacterial community in soil planted with Cry1Ac expressing Bt brinjal. However, no effort has been made to assess the effect of Bt brinjal on fungal community structure (diversity and density).…”