Temporal dynamics of microbial communities in the rhizosphere of two genetically modified (GM) maize hybrids in tropical agrosystems

Abstract

The use of genetically modified (GM) plants still raises concerns about their environmental impact. The present study aimed to evaluate the possible effects of GM maize, in comparison to the parental line, on the structure and abundance of microbial communities in the rhizosphere. Moreover, the effect of soil type was addressed. For this purpose, the bacterial and fungal communities associated with the rhizosphere of GM plants were compared by culture-independent methodologies to the near-isogenic parental line. Two different soils and three stages of plant development in two different periods of the year were included. As evidenced by principal components analysis (PCA) of the PCR-DGGE profiles of evaluated community, clear differences occurred in these rhizosphere communities between soils and the periods of the year that maize was cultivated. However, there were no discernible effects of the GM lines as compared to the parental line. For all microbial communities evaluated, soil type and the period of the year that the maize was cultivated were the main factors that influenced their structures. No differences were observed in the abundances of total bacteria between the rhizospheres of GM and parental plant lines.

The plant microbiome

“…This highlights that a small change in plant genotype can have complex and unforeseen effects on the plant microbiome. Other studies have not found any significant differences in rhizosphere microbiomes between wild-type maize and maize genetically engineered to produce Bacillus thuringiensis (Bt) toxin [100,101], although this may be due to Bt toxin being insecticidal rather than antibacterial. Also, in the wheat rhizosphere, introduction of the pm3b gene conferring resistance to mildew had minimal effect on pseudomonads and mycorrhizal fungi populations [102].…”

Exploring interactions of plant microbiomes

“…That finding was directly related to the metabolic differences observed between the two plant genotypes, which can also account for changes observed in plants from distinct genotypes within the same species (i.e., varieties, cultivars). Based on that, the differential selection driven by plant genotype has been extensively used to track the safety issues for the cultivation of transgenic plants (Rasche et al, 2006;Cotta et al, 2013;Arpaia et al, 2014), with many studies indicating limited or low effects of the exogenous genes on the plant-associated communities. In contrast to these observations, differences in the composition of microbial communities in the rhizosphere of Arabidopsis thaliana are likely to be determined by soil type, rather than a unique selection by plant genotype (Lundberg et al, 2012).…”

“…2008;Chaparro et al, 2014). For instance, the developmental stage of maize plants is a stronger driver of the bacterial community composition in the rhizosphere than the soil type and plant genotype (Cotta et al, 2013). Andreote et al (2010) studied the roles of bacterial inoculation, plant genotype and the developmental stage of the colonization of plant roots (in both rhizosphere and endosphere) by bacterial communities and found the composition of bacterial communities in potato to be mostly driven by the plant genotype (it differed according to the use of distinct varieties) and plant developmental stage (from vegetative to senescent stages).…”

Annual replication is essential in evaluating the response of the soil microbiome to the genetic modification of maize in different biogeographical regions

“…The rhizomicrobiome of maize MON810 in different genetic backgrounds and in relation to near-isogenic cultivars as comparators has already been studied at a number of field sites located in different climatic regions, including Portugal, Spain, Slovakia, the USA, Brazil or Germany [18,[20][21][22][23][24][25], and an effect of the…”