Category: Breeding

A review paper in the latest Agriculture, Ecosystems and Environment looks at what climate change will do to wheat, and what can be done about it. ((ORTIZ, R. et al. (2008). Climate change: Can wheat beat the heat?. Agriculture, Ecosystems & Environment. DOI: 10.1016/j.agee.2008.01.019)) The lead author is deputy director general at the International Centre for Maize and Wheat Improvement (CIMMYT), and the picture he paints must be keeping him up at nights.

There are 12 different types of places where wheat is grown around the world — so-called “mega-environments.” They range from “high rainfall, hot” (e.g. in Bangladesh) to “low rainfall, severe cold” (around Ankara in Turkey). Some are better than others. One of the best is mega-environment 1, which amounts to 32 million hectares in northwest Mexico, the Indo-Gangetic Plains and the Nile Valley. It accounts for 15% of global wheat production, and it is in trouble.

When you look at the likely 2050 climate, half of the area of the Indo-Gangetic Plains which is now in mega-environment 1 might well need to be re-classified from pretty ideal low rainfall, irrigated, temperate to heat-stressed, short season. That is, conditions will look more like the Gezira in Sudan or Kano in Nigeria. That will reduce yields, affecting 200 million people.

So wheat breeders will have to develop varieties that can maintain yields under higher temperatures, unless you want farmers to switch to another crop entirely. Which might be the easiest thing in some places, actually, but that’s another story.

You can breed for resistance to an abiotic stress such as heat by growing a wide range of genotypes under that stress and looking for the highest yielding genotypes, of course. But what breeders at CIMMYT are now increasingly doing is trying to identify the different physiological attributes which are associated with high yield under stress conditions — things like leaf chlorophyll content during grain filling, for example. And then stacking them up together in new varieties. That’s had some success in breeding for drought resistance. Let’s hope — for the sake of Indian wheat farmers — that it works for heat too.