Monoculture and the Irish Potato Famine: Cases of missing genetic variation (2 of 3)

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The Importance of Diversity
The genetically identical lumpers were all susceptible to a rot caused by Phytophthora infestans, which turns non-resistant potatoes to inedible slime. Because Ireland was so dependent on the potato, one in eight Irish people died of starvation in three years during the Irish potato famine of the 1840s.

Although the famine ultimately had many causes, the disaster would likely not have been so terrible had more genetically variable potatoes been planted. Some potatoes would have carried the right genes to make it through the epidemic, and more of the resistant varieties could have been planted in the years following the first epidemic. Later, scientists identified resistance genes in a potato from South America, where farmers have preserved the genetic variation of potatoes by growing many cultivated varieties alongside the potato’s wild cousins.

The image below compares the effect of a blight on diverse and cloned crops.

Diverse and cloned potato patches

 

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Spanish translation of Understanding Evolution For Teachers from the Spanish Society of Evolutionary Biology.