In the wild, interbreeding is one of the ways plants remain genetically diverse. Domesticated crops don't do this, so they have far less genetic diversity. If an illness can kill one of them, it likely can kill them all—so without diverse genes for disease resistance, domesticated plants like wheat and oats are vulnerable to contagion. As crops became domesticated, they also became genetically dissimilar from their wild relatives in ways that prevent the two from interbreeding. The biggest effect of this is food instability: whole crops can be quickly wiped out by diseases. In Bangladesh, for instance, wheat blast—a fungus endemic to South America—arrived in 2016 and has already done serious damage in a region of the world where the rate of people who are malnourished is high.