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GUEST AUTHOR: Terry Daynard | Ontario grain farmer. Former University of Guelph crop science professor and associate dean | tdaynard.com | @terrydaynard
This piece previously appeared on Terry Daynard’s blog. It appears here by permission of the author.
Whoever thought that France and organic agriculture would be world leaders for the introduction of GE (genetically engineered) wheat? A stretch? Not as much as it might seem. What follows is the story of how plant breeders engineered a unlikely new crop through a series of sophisticated “conventional” techniques to move a use gene from a wild plant into wheat, despite the fact that the two plants could not be naturally crossbred.
Here’s my summary of “Un blé bio génétiquement modifié, ça existe déjà.” The article describes in detail how a popular European organic wheat variety was created using transgenic techniques. In fact, this organic wheat variety may be the only GE (genetically engineered) wheat commercially available in the world.
Readers should bear in mind that I am fluent in neither French nor genetics but have a passable understanding of both. The following summary includes some comments from me (all in parenthesis) to add clarity for readers possessing an even poorer understanding of genetics than do I.
The variety is ‘Renan’ which is apparently popular with organic wheat growers in France and German, in part because of its good genetic resistance to several types of rust and ‘eye spot’ disease. The most notable difference between Renan and other types of GE transgenic events is that Renan has small pieces of chromosomes transferred from another species which will not cross naturally with bread wheat (Triticum aestivum) – compared to single transferred genes as with other GE events/varieties (examples, Bt corn/cotton, herbicide-tolerant crops and ‘Golden Rice’).
How Renan was derived
The story starts at le laboratoire de cytogénétique de Versailles in the late 1940s as part of its search for genetic resistance to several species of rust and other wheat diseases. They found some excellent resistance to these diseases and other pathogens in a wild grass, Aegilops venticosa.
Unfortunately, this species will not cross with T. aestivum. To get around this, they transferred chromosomes of A. venticosa into a third species, Triticum carthicum which will cross with T. aestivum.
Unfortunately the resulting crosses between A. venticosa and T. carthicum were sterile, equivalent to mules created when crossing horses and donkeys. To get around this, they treated the crossed florets with a chemical, colchicine, which doubles the chromosome number. (That’s a technique used commonly to induce seed formation in other such ‘wide crosses.’)
The seed-producing plants thus derived were then crossed with a wheat (T. aestivum) variety. The next intended step was backcrosses to T. aestivum in order to produce a ‘genome’ which was mostly wheat but which contained the valuable genes and associated chromosome segments transferred from the wild grass. However, backcrossing proved to be very difficult because the A venticosa chromosomes would not pair with those of T. aestivum. To get around that, they exposed the seeds or florets to X rays which broke chromosomes (or at least some of them) into smaller segments, and backcrossing was then able to proceed successfully.
The result was a form of ‘T. aestivum’ which contained two segments of A. venticosa chromosomes – one segment on one wheat chromosome containing genes resistance to several rust species, and a second segment on another wheat chromosome containing the gene Pch1 giving resistance to eye spot. Further research showed that, although the ‘genome’ after several cycles of backcrossing was largely wheat (plus two inserted segments), the cytoplasm was essentially that of A. venticosa, the wild species.
This ‘wheat’ was then made available for commercial usage – interesting after no testing at all for human or animal safety, allergens or whatever – and little or no knowledge of the other genetic material transferred from the wild species.
The wheat was then crossed with Moisson, a popular wheat variety of the day, to produce a variety called Roazon, released in 1976. Roazon did not enjoy much commercial success, but it in turn was used to breed Renan, released in 1989. Renan has been a very popular variety, especially in organic agriculture in large part because of the chromosome segments containing rust and eye spot resistant genes.
So what’s the difference between Renan and many other GE crop varieties? Not much it appears except for the fact that Renan contains much more transgenic material, has not undergone the large amount of testing for safety and environmental impact as other GE events, and little is known about the mechanisms of the transferred genes.
Think of that while you enjoy your baguette at an organic café sur la Rive Gauche, Paris.
Author’s note: I am indebted to Emmanuel Ferrand, St Pourçain sur Sioule, Allier, France (@E_Ferrand_03) for making me aware of this article.
[Please consider supporting Food and Farm Discussion Lab with an ongoing contribution of $1, $2, $3, $5 or $10 a month on Patreon. All contributors receive a subscription to our email newsletter the FAFDL Dispatch. ]
