Stem rust is a devastating disease that can cause wheat crops to fail completely. The fungus produces spores that are easily dispersed by the wind, and can infect wheat plants at any stage of growth. Once infected, the plants develop yellow-brown stripes on their stems and leaves, and their heads fill with black spores.
The most common way that wheat resists stem rust is through a genetic trait called resistance. Resistance genes code for proteins that recognize the fungus and trigger a defense response, which prevents the fungus from spreading. However, the fungus can evolve to overcome these resistance genes, and new races of stem rust are constantly emerging.
In the 1990s, a new race of stem rust called Ug99 emerged in Africa. Ug99 is particularly virulent, and it has the potential to cause widespread damage to wheat crops around the world. In 2016, Ug99 was detected in Yemen, and it is now spreading to other countries in the Middle East.
The spread of Ug99 is a major threat to global food security. Wheat is a staple food for billions of people around the world, and a stem rust pandemic could cause widespread famine. Scientists are working to develop new wheat varieties that are resistant to Ug99, but it is a race against time.
Here is a timeline of the evolutionary battle between wheat and stem rust:
10,000 BC: Wheat is domesticated in the Middle East.
5,000 BC: Stem rust emerges as a disease of wheat.
1900s: New races of stem rust emerge that are able to overcome the resistance genes in wheat.
1990s: Ug99, a particularly virulent race of stem rust, emerges in Africa.
2016: Ug99 is detected in Yemen.
Today: Ug99 is spreading to other countries in the Middle East and poses a major threat to global food security.
The wheat-stem rust battle is a classic example of coevolution. As the wheat evolves new defenses, the stem rust evolves new ways to overcome them. This arms race has been going on for thousands of years, and it is still too early to say who will ultimately win.
