Domestic breeding has been a 'powerful evolutionary force' on our food plants, to which the introduction of GM plants has added a whole new dimension. Noting this, a Mexican team of scientists took a look at the extent of the changes now present in conventional and GM crops compared to their wild ancestors.
Six key fitness traits were identified for which a body of data was available: plant height, number of flowers, days to flowering, number of seeds, pollen viability and number of fruits. A literature search found 120 suitable studies (representing 990 comparisons) covering five economically and culturally important crops: rice, canola, maize, sunflower and pumpkin. The data were merged in a meta-analysis to demonstrate how human intervention has altered the characteristics of our food crops.
What the team expected to find was a large pool of diversity in the wild-type, with a much narrower variation selected for during domestication. In charts showing the range of traits, this should make our crops appear as a sub-group nested within their ancestors. Since GM plants have a single, precisely constructed gene change and are derived from single elite lines, their trait variation was expected to be even more limited and to appear nested within the features of their non-GM counterpart.
In fact, what they found was that only one crop, canola, fitted this expectation of sub-grouping (see Note). Rice had almost no overlap between the wild type and the domesticated. Three crops (sunflower, pumpkin and maize) showed almost no overlap of traits between GM and non-GM versions. One crop (sunflower) showed increased variation in the GM forms.
GM crops have foreign DNA for the expression of simple specific traits such as virus-resistance, insect-resistance or herbicide-tolerance. None of these novel genes is designed to, nor expected to, alter any of the six key characteristics used in the meta-analysis. Yet, statistically significant differences between GM and non-GM plants were found in almost all crops and traits. These were described as being "most dramatic" in rice, pumpkin and maize where most analysed traits differed significantly.
The authors point out that their findings make nonsense of the suggestion that any GM crop is "substantially equivalent" to its closest non-GM counterpart: the two grow and reproduce quite differently.
OUR COMMENTIt seems the concept of substantial equivalence as some sort of proof of the safety of a GM crop, is scientifically-indefensible wishful thinking. We need SAFETY TESTING.
The meta-analysis suggests a huge latent potential in wild-type genomes to generate plants with characteristics not predictable from any knowledge of individual or small subsets of genes. For the future of farming and our food supply, it's imperative that we recognise the importance of the wild gene pool UNADULTERATED BY FOREIGN MAN-MADE DNA OR BY DNA-EDITING.
Note on canola.We can only speculate why canola should be the only crop to show the expected reductions in trait diversity due to domestication and genetic transformation. However, canola is a variety of rapeseed and, unlike the other four crops in the study which all have a very long history of use as staple human foods and associated breeding, canola is a newcomer.
Rapeseed is thought to have been introduced to the UK by the Romans, but no one's saying what they used it for: the oil has a bad taste, an unhealthy fat profile, and a toxin. Use of rapeseed dwindled until the Middle Ages when it was found to be a good 'break crop' (meaning it was grown in order to keep the weeds down and then dug in to improve the soil). During the Industrial Revolution, rapeseed oil was used to lubricate engines, and the seed were used to feed animals. There was little incentive up until then for farmers to breed changes into the crop.
In the 1960s and 70s, Canadian plant breeders developed a highly specialised strain of oilseed rape with a healthy fat content, no toxin and no nasty taste. They registered it as 'canola', a contraction of CAN from Canada and OLA from 'oil low acid'.
Canola's history and recent registration as a controlled plant breed for human consumption may well have contributed to the finding of a narrowed trait variation within the range of its domestic and wild ancestors.
GM oilseed rape has a history of introgressing into natural populations. Could its apparent similarity to its older relatives be easing the way to gene flow?
- Alejandra Hernández, et al., 2017, Domesticated, Genetically Engineered, and Wild Plant Relatives Exhibit unintended Phenotypic Differences: A Comparative Meta-Analysis Profiling Rice, Canola, Maize, Sunflower, and Pumpkin, Frontiers in Plant Science
- New meta-analysis reveals extensive phenotypic differences between GMO and non-GMO cultivated plants, GM Watch 6.06.18
- Research reveals new dimension in environmental risk posed by genetically engineered plants, www.testbiotech.org, 6.04.18
- Oscar Harding, Rapeseen - A Brief History, www.duchessoil.co.uk, 1.06.16
- Canola History, Northern Canola Growers Association
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