Roundup weedkiller and Roundup Ready crops

The world’s most popular weedkiller is called Roundup. It’s used in gardens, on farms and in public places. Many of the world’s most popular genetically modified (GM, genetically engineered) crops are called Roundup Ready. You can spray these crops with Roundup and they’ll be fine, while weeds die.

This weedkiller’s active ingredient is glyphosate (N-phosphonomethyl-glycine). Here’s how it works. It blocks a chain of biochemical events, called the shikimic acid pathway, which plants need to stay alive. So this is a ‘broad-spectrum’ weedkiller. It kills grassy plants (monocotyledons), herby plants (dicotyledons) and coniferous plants (gymnosperms). Glyphosate doesn’t dissolve easily in water. So it’s usually sold as one of several water-soluble salts. Those glyphosate salts are mixed with ‘surfactants’ to help them stick to, and cross, plants’ outer layer of wax.

Chemical companies including Monsanto, Bayer and Syngenta make and sell glyphosate weedkillers. Here’s a history of glyphosate explaining how, since Monsanto’s patent on glyphosate expired in 2000, other companies have been selling it. ‘In some European countries, for example in the UK and Germany, farmers use glyphosate for crop management on up to 40 per cent of the total agricultural acreage.’

Sometimes when people spray weedkiller, they don’t want to kill everything. Sometimes they want to grow crops. Here comes GM.

The, er, catchily named International Service for the Acquisition of Agri-Biotech Applications (ISAAA) tells us how GM glyphosate resistance works. The crops have been engineered to carry a gene called cp4 epsps. It’s named ‘cp4‘ because the gene originated in a bacterium called Agrobacterium tumefaciens strain CP4. It’s named ‘epsps‘ because its product binds to an enzyme in the shikimic acid pathway called 5-enolpyruvulshikimate-3-phosphate synthase (EPSPS). Also, having originated in that particular strain of A. tumefaciens, the gene is sometimes named aroA:CP4.

Now I’ll summarise what ISAAA does. Please tell me if I’ve misunderstood. I think that ISAAA registers any GM success in a lab as an ‘event’. After safety testing, I think that ISAAA registers approved GM crop varieties as ‘crops’. List of ‘events’ and ‘crops’ are published in the ISAAA approval database.

From that database, here are the successful glyphosate-tolerance events and here are the approved glyphosate-tolerant crops. If you click on the ‘Trade Names’ column you’ll see that most of these crops, but not all of them, are from Monsanto.

As I’ve mentioned once or twice ;-), its GM crops have made Monsanto the world’s most hated company. Hate it or love it, Monsanto is selling Roundup Ready crops and farmers are growing them.

Advertisement