Natural Variability of Metabolites in Maize Grain:  Differences Due to Genetic Background

Abstract

Understanding the impact of genetic diversity on crop biochemical composition is a prerequisite to the interpretation and potential relevance of biochemical differences experimentally observed between genotypes. This is particularly important in the context of comparative safety assessments for crops developed by new technologies such as genetic engineering. To interrogate the natural variability of biochemical composition, grain from seven maize hybrids grown at four geographically distinct sites in Europe was analyzed for levels of proximates (fat, protein, moisture, ash, and carbohydrates), fiber, amino acids, fatty acids, four vitamins, nine minerals, and secondary metabolites. Statistical evaluation of the compositional data at the p < 0.05 level compared each hybrid against every other hybrid (head-to-head) for all analytes at each site and then across all sites to understand the factors contributing to variability. Of the 4935 statistical comparisons made in this study, 40% (1986) were found to be significant. The magnitude of differences observed, as a percent, ranged between 0.84 and 149% when all individual sites and the combined sites were considered. The large number of statistically significant differences in the levels of these analytes between seven commercial hybrids emphasizes the importance of genetic background and environment as determinants of the biochemical composition of maize grain, reflects the inherent natural variability in those analytes across a representative sampling of maize hybrids, and provides a baseline of the natural range of these nutritional and antinutritional components in maize for comparative compositional assessments.

Opinion of the Scientific Panel on Genetically Modified Organisms on applications (references EFSA-GMO-UK-2005-19 and EFSA-GMO-RX-GA21) for the placing on the market of glyphosate-tolerant genetically modified maize GA21, for food and feed uses, import an

“…However, none of these differences were consistently observed over years and at each location. The levels of those compounds that differed from the levels in the corresponding non GM control were within the normal ranges reported in the literature for commercial maize varieties (OECD, 2002;Reynolds et al, 2005).…”

Analysis of Chiral Amino Acids in Conventional and Transgenic Maize

“…It can be observed from the results given in Table 3 that the different conventional varieties (Aristis, Tietar, PR33P66) show different profiles of L-and D-aa, what seems to corroborate the natural variability expected. 38 This result was corroborated with the one-way ANOVA and posterior LSD test indicating that the three samples were statistically different (P < 0.05) in all cases except for the % D-Glu for which no significant differences were observed. Next, a comparison was established between the different couples of samples (i.e., conventional maize vs its corresponding Bt variety) using the twosample t-test.…”

Interaction of Genetic Mechanisms Regulating Methionine Concentration in Maize Grain

“…The results of Reynolds et al (2005) suggest the variability in amino acid levels among commercial hybrids is controlled by the genetic background and growing conditions. Taken together, these studies suggest it should be possible to use plant breeding methods to alter the methionine concentration in breeding populations.…”