Irradiated seeds combat world’s most serious wheat disease

Wheat (Triticum spp.) is a staple food in many parts of the world. You can follow my ‘wheat’ tag for more about this crop. Now there are two new varieties to resist a devastating wheat disease.

If you’re growing wheat, you really don’t want the disease called wheat stem rust or black stem rust. That’s caused by a fungus, Puccinia graminis tritici. The International Maize and Wheat Improvement Center (CIMMYT, its Spanish acronym) tells us how badly wheat stem rust can damage crops. ‘Had there not been investment in stem rust research and ensuing effective global control during 1961-2009, losses in wheat production would have amounted to 6.2 million tons annually, or 1.3% of the total harvest. This equates to losses of US $1.12 billion per year at 2010 prices, or enough wheat to satisfy almost the entire annual calorie deficit of sub-Saharan Africa’s undernourished population.’

[Edit] That’s an example of how hunger isn’t about an overall shortage of food in the world, isn’t it? Wheat was grown but the hungry people didn’t get to eat it.

The battle against wheat stem rust looked quite promising until the late 1990s. Then evolution gave the farmers a new ‘race’ of P. graminis tritici which has the, er, catchy name Ug99. This race of this fungus got named when it was identified in Uganda in 1998. I suppose these scientists got around to naming it a year after finding it! Here’s the science.

Now here are two rust-resistant wheat varieties. Miriam Kinyua and her team who gave us these wheat varieties didn’t use genetic modification (GM, also called genetic engineering or GE.) But another research group made GM wheat carrying a gene called Sr35, which causes the plants to resist rust. It’s not yet available for commercial planting. I don’t know whether it ever will be.

Meanwhile, Prof Kinyua’s team didn’t use GM. They made Ug99-resistant wheats by a different kind of biotechnology, mutation breeding (MB). They exposed wheat seeds to radiation, causing their DNA to mutate more quickly than it would otherwise do. Then they selected embryos and grew them into wheat plants. I’ve mentioned before how MB can assist conventional plant breeding without entering the minefield of GM controversy.

Which embryos did Prof Kinyua’s team choose? Obviously, the ones whose mutated DNA made them resistant to the dreaded Ug99 rust. I don’t know which mutations the chosen embryos carried but Ug99 didn’t kill them.

These wheat varieties won’t work forever because the fungus will keep evolving. But Prof Kinyua and other scientists can keep using MB to develop more wheats. They might not even need to do that, if these wheats happen to evolve faster than the fungus.

This is why I’m so impressed by MB. ‘With these seeds, farmers only have to purchase or trade for them once. After their first plantings, they may keep some of the grains to plant as next year’s crops.’ So these experts on the ground can select the best plants and trade them with other farmers. That’s how local varieties come to be.

This is the first time I’ve found a story through Twitter! I’m grateful to @RosePastore who tweets @PopSci for telling us about the new wheat varieties.


About argylesock

I wrote a PhD about veterinary parasitology so that's the starting point for this blog. But I'm now branching out into other areas of biology and into popular science writing. I'll write here about science that happens in landscapes, particularly farmland, and about science involving interspecific interactions. Datasets and statistics get my attention. Exactly where this blog will lead? That's a journey that I'm on and I hope you'll come with me.
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