Wednesday, 21 April 2021 08:24

Plant breeding: 10,000 years of biodiversity threats?

The opposition to modern breeding technologies is strong in Europe; however, it is not based on scientific facts. As soon as a serious flaw in the arguments is exposed, activists are moving the goalposts. From non-existent health dangers, the focus has now shifted to biodiversity threats. But is there really any risk from the new technologies via “genetic contamination”?

For years, NGOs and politicians opposing modern breeding methods such as gene transfer or genome editing have claimed that these “manipulations” would pose serious health risks, from allergies to cancer or autism. However, after more than two decades of consuming transgenic crops, there is not a single confirmed case of adverse health effects caused by precision-bred plants.

As a result, the focus of opposition has silently shifted to another alleged threat. Precision-bred plants, it is claimed, can cross-pollinate other varieties or even „contaminate“ crop wild relatives, thereby threatening biodiversity and narrowing the genetic diversity.

This is a very strange notion. For 10,000 years, humans have bred new varieties from wild plants, using a new genetic variation, including mutations to generate plants with entirely different properties that suit the needs of farmers and consumers.

All cabbage e.g. is based on an inconspicuous, tender crucifer that is still found today. We have grotesquely changed it: We thickened the shoot (kohlrabi), enlarged the leaves (palm kale), or compressed the shoot so much that the leaves grow over and into each other (white cabbage, red cabbage, savoy cabbage). In cauliflower, broccoli and Romanesco, it is the greatly enlarged inflorescences we eat; in Brussels sprouts, it’s the leaves of the compressed side shoot.

Today’s carrot no longer even has the colour in common with the wild carrot, whose roots are barely pencil-thick, whitish and with a soap-like taste. All our cereals, too, are based on a profound change: In contrast to their wild relatives, they no longer spread their seeds. The grains remain so firmly on the stalk that the plants can be harvested and transported without grain loss. As a result, considerable mechanical force is required to subsequently remove them by threshing.

With corn, it took decades for researchers to realize that corn probably was bred from a small grass called teosinte. Thousands of years before the arrival of Columbus the inhabitants of Central America had already bred from this plant the modern corn which we know today in form of several hundred varieties.

Today we know, that often only a few mutations are sufficient to introduce huge morphological changes. If the introduction of these genetic changes was a threat to biodiversity, one would expect that in 10,0000 years of agriculture all these novel genetic traits had been transferred to crop wild relatives by cross-pollination, so that they got extinct. But we don’t see this effect: Teosinte, wild cabbage, wild carrots – they are still thriving today although cross-fertilization with modern varieties would still be possible.

Although this might even occur in nature it obviously does not have a lasting effect as all these mutations are beneficial for farmers and consumers but in the long run detrimental for the plants in their natural environment. Not losing the seeds any more would be the end of any wild grass; becoming less bitter and more nutritious is attracting all sorts of predators, changing the colour of the flowers could attract the wrong or no pollinators at all.

This also holds for resistances against viruses as in nature every resistance is temporarily only. Like with the Coronavirus, evolution will inevitably lead to insects and pests able to override resistances by mutating. This is why crop improvement is always a race against time. Until today, hundreds of naturally occurring resistance genes against plant viruses have been reported, and for at least 80 years being introduced to cultivars via conventional breeding. Why would anyone expect that the introduction of these genes via precision breeding would lead to a different outcome? Why are there no complaints about virus-resistant varieties in general?

This short reminder of the history of our current crops and vegetables clearly demonstrates that the introduction of novel traits to agricultural plants should be judged by the trait and not the method used to introduce it – all the more so as conventional breeding is known to change hundreds, if not several thousands of genes.

It also demonstrates once again that the opposition to modern precision breeding is not based on facts, but on unfounded fears. Considering the challenges ahead – climate change, as well as the tough political goals EU policymakers, have laid down in the Farm to Fork strategy – these unfounded fears should no longer stand in the way of innovations in plant breeding.