Assessment of potential impacts associated with gene flow from transgenic hybrids to Mexican maize landraces

Impact of genetically modified herbicide-resistant maize on rhizosphere bacterial communities

Rhizosphere bacterial community studies offer valuable insights into the environmental implications of genetically modified (GM) crops. This study compared the effects of a non-GM maize cultivar, namely Hi-IIA, with those of a herbicide-resistant maize cultivar containing the phosphinothricin N-acetyltransferase gene on the rhizosphere bacterial community across growth stages. 16s rRNA amplicon sequencing and data analysis tools revealed no significant differences in bacterial community composition or diversity between the cultivars. Principal component analysis revealed that differences in community structure were driven by plant growth stages rather than plant type. Polymerase chain reaction analysis was conducted to examine the potential horizontal transfer of the introduced gene from the GM maize to rhizosphere microorganisms; however, the introduced gene was not detected in the soil genomic DNA. Overall, the environmental impact of GM maize, particularly on soil microorganisms, is negligible, and the cultivation of GM maize does not alter significantly the rhizosphere bacterial community.

Novel Combination of the Biophysical, Nutritional, and Nutraceutical Properties in Subtropical Pigmented Maize Hybrids

Maize (Zea mays L.) represents the main caloric source for much of the world's population. Pigmented maize varieties are an excellent source of nutraceutical compounds: blue and yellow maize are rich in anthocyanins as well as carotenoids and phenolic acids, respectively. However, blue maize is usually grown in small quantities as a specialty crop because it lacks the qualities and adaptations of commercial white and yellow varieties. Here, a new high-yield variety of blue maize called Vitamaiz was developed from inbred lines of subtropical blue, white, and yellow maize. The aim of this study was to characterize the nutraceutical and physical properties of 30 Vitamaiz hybrids in two subtropical locations. Kernel physical traits, nutrient composition, and nutraceutical components (free phenolic acids, FPA; cell wall-bound phenolic acids, BPA; total monomeric anthocyanin content, TAC; antioxidant capacity, AOX by oxygen radical absorbance capacity assay, and total carotenoid content, TCC) were evaluated. The biophysical traits of the hybrids were suitable for nixtamalized and flour maize industries. High levels of FPA (228 mg GAE/100 g), BPA (635 mg GAE/100 g), and AOX (2.0 and 8.1 mM Trolox equivalent/100 g for FPA and BPA, respectively) were also detected with elevated TAC levels (274 mg C3G/kg dw) and AOX activity (3.1 mM Trolox equivalent/100 g). This is the first study to characterize Blue × Yellow maize hybrids that adapt to subtropical environments.

Transgene Flow: Challenges to the On-Farm Conservation of Maize Landraces in the Brazilian Semi-Arid Region

Brazil is one of the largest global producers of genetically modified crops and a center of origin and diversification of relevant species for agriculture and food. Transgenic monocultures occupy around 50 million hectares, whereas smallholder farmers, indigenous people, and traditional communities are responsible for in-situ/on-Farm conservation of local genetic resources. Based on 15 years of expertise in regulating GMOs and in cross-institutional agrobiodiversity conservation projects, this article discusses the challenges regarding the coexistence of these two agricultural models based on transgene flow detection in maize landraces. As part of a broad and unique participatory transgene-flow-monitoring process, 1098 samples of maize landraces were collected in the Brazilian Semi-arid Region between 2018 and 2021 and analyzed using immunochromatographic strips. The tests revealed 34% of samples with presence of GM proteins. It is concluded that the biosafety standards in force in Brazil do not allow the assurance of on-Farm conservation of maize. The sectors that contribute to agrobiodiversity conservation and do not benefit from using GM seeds are taking on the burden of this process. Transgene flow can be reduced by approving and enforcing more effective coexistence rules that consider maize landraces crop areas also as seed-producing areas added to full disclosure of commercial seeds origin.

Should we still worry about the safety of GMO foods? Why and why not? A review

Global population is increasing at an alarming rate, posing a threat on the supplies of basic needs and services. However, population increase does not seem to be a common agendum of the global scientists and political leaders. People in the developed countries are more concerned about new technologies and their products. Pseudo-threats related to the uncertainties of genetic engineering of crops and their outputs present on consumers are more audible and controversial than the real difficulties the world is experiencing at the moment and in the future. This review presents brief summaries of the real reasons to worry about and the uncertainties about genetically modified organisms. This article also presents the real uncertainties shared by consumers and scientists with respect to the past, present, and future of genetically engineered organisms. Developments in the field of precision genetics in the recent years and the implications on regulatory, breeding, and socio-cultural dimensions of the global settings are included.

Compositional Variation in Trans-Ferulic, p-coumaric, and Diferulic Acids Levels Among Kernels of Modern and Traditional Maize (Zea mays L.) Hybrids

Maize is one of the most heterogenous cereals worldwide in terms of yield, physical characteristics, and biochemical composition due to its natural diversity. Nowadays the use of maize hybrids is extensive, while the use of landraces is mostly local. Both have become an important genetic resource useful to identify or generate varieties with desirable characteristics to overcome challenges of agronomic performance, nutritional quality, and functionality. In terms of functionality, one of the most studied families of compounds are phenolic acids. These compounds have been associated with the improvement of human health because of their antioxidant capacity. To evaluate the diversity of phenolic compounds in maize, two collections, the Nested Association Mapping (NAM) founders and 24 landraces, were crossed with B73. Phenolic compounds were extracted and quantified by HPLC-PDA. Soluble and cell wall phenolic acids were identified and significant differences between and within the NAM and Landrace collections were assessed. Soluble p-coumaric acid quantification of B73 × NAM hybrids presented high variation as the range went from 14.45 to 132.34 μg/ g dw. In the case of B73 × Landrace hybrids, wide variation was also found, ranging 25.77-120.80 μg/g dw. For trans-ferulic acid, significant variation was found in both hybrid groups: B73 × NAM presented an average of 157.44 μg/g dw (61.02-411.13 μg/g dw) whereas the B73 × Landrace hybrids average was 138.02 μg/g dw (49.32-476.28 μg/g dw). In cell wall p-coumaric acid, a range from 30.93 to 83.69 μg/g dw and 45.06 to 94.98 μg/g dw was found for landrace and NAM hybrids, respectively. For cell wall trans-ferulic acid, a range from 1,641.47 to 2,737.38 μg/g dw and 826.07 to 2,536.40 μg/g dw was observed for landrace and NAM hybrids, respectively. Significant differences between hybrid groups were found in p-coumaric acid, for both soluble and cell wall-bounded. Therefore, maize hybrids produced by conventional techniques using both modern and traditional varieties showed a high diversity in terms of phenolic compounds, denoting the role of these compounds in the maize ability to endure different environment conditions. This study provides a platform of comparison through the unveiling of maize phenolic compounds for future breeding efforts.

Transgene behavior in Zea mays L. crosses across different genetic backgrounds: Segregation patterns, cry1Ab transgene expression, insecticidal protein concentration and bioactivity against insect pests

Brazil and South Africa, countries with economies in transition, are characterized by a dual agrarian structure co-occurring, sometimes, alongside in the same region. Large-scale commercial farming produces crops for export to global markets on the one hand, and small-scale farming, on the other hand, provides for subsistence and local markets. In both systems, maize (Zea mays) is a key crop for these two countries. For the commercial system, maize is a commodity crop while for the small-scale system it is the prime staple crop. In commercial systems, farmers predominantly grow genetically modified (GM) hybrid maize. In small-scale systems, farmers rely on open pollinated varieties (OPVs) and/or landraces and are largely dependent on seed saving systems. The aim of this study was to understand the relationship between transgene expression rates, the resulting concentrations of the transgene product (Bt protein) and its bioactivity in insect pests following transgene flow from GM hybrid maize into non-genetically modified, non-GM near-isogenic maize hybrid (ISO) and OPVs. We modeled segregation patterns and measured cry1Ab transgene expression (mRNA quantification), Cry1Ab protein concentration and pest survival. Two groups of F1, F2 crosses and backcrosses with GM, ISO and OPV maize varieties from Brazil and South Africa were used. Bioassays with the larvae of two lepidopteran maize pest species, Helicoverpa armigera and Spodoptera littoralis, were carried out. Overall, the cry1Ab transgene outcrossed effectively into the genetic backgrounds tested. The cry1Ab transgene was stably expressed in both ISO and OPV genetic backgrounds. Transgene introgression led to consistent, though highly variable, concentrations of Cry1Ab toxins that were similar to those observed in GM parental maize. Most crosses, but not all, suggested the expected Mendelian segregation pattern. Transgene expression rates were significantly higher than expected from purely Mendelian segregation in the South African crosses. In South African materials, ISO and OPV crosses produced significantly lower Cry1Ab concentrations compared to the GM parental maize. The Cry1Ab toxins from crosses were bioactive and induced mortality rates of ≥92.19% in H. armigera and ≥40.63% in S. littoralis after a period of only 4 days. However, no correlations were observed between the quantitation of mRNA for cry1Ab and the corresponding Cry1Ab protein concentrations, nor between the Cry1Ab concentrations and insect mortality rates across different genetic backgrounds. We therefore suggest that while transcription of the cry1Ab transgene reliably determines the presence of Cry1Ab protein, mRNA levels do not reflect, by themselves, the end Cry1Ab protein concentrations found in the plant. Because predictably high Cry1Ab concentrations are a key prerequisite for effective insect resistance management (IRM) programs, this observation raises questions about the effectiveness of such programs in scenarios with complex crop genetic backgrounds. On the other hand, confirmed bioactivity in all crosses should be expected to impact small farmer's selection behavior, unknowingly favoring the insecticidal trait. This may lead to a fixation of the trait in the wider population, and may influence the genetic diversity of varieties maintained by small-scale farmers.