The period from 1845 to 1852 is one of great misfortune in Ireland’s history. Occurring only one major time before, the Irish Famine wreaked havoc on Ireland’s demography, culture, and politics. But what was the source for this catastrophic event? Potatoes. During the Famine, many of the potatoes rotted, turned black, and their leaves withered. It was only 168 years after the Famine that scientists finally discovered the cause.
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Scientists have known that it was a strain of Phytophthora infestans that caused the famine. However, the exact strain remained unknown until 2013. Scientists previously believed that the strain, US-1, had been the culprit. So scientists studied DNA from eleven different samples of potato leaves, dating back as far as 1845. The entire genome of Phytophthora infestans and the potato were sequenced in only a few weeks. Scientists then compared the genomes to modern Phytophthora strains from Europe, Africa and the Americas. This was the first time that an ancient plant genome had been successfully sequenced. Based on these results, scientists concluded that it was not US-1 that had caused the famine, but the HERB-1 strain. The HERB-1 strain originated in Mexico’s Toluca Valley and it was not until the 1840’s that the strain arrived in Europe.
One of the reasons for Ireland’s devastation due to the famine was its dependence on potatoes. In the decades preceding the Great Famine, many smaller blights had occurred. This did not prove to be severely problematic as many countries grew a variety of potatoes. However, Ireland did not. They were dependent upon one type of potato: The Irish Lumper. Because of this reliance, the loss of such a large crop of potatoes was disastrous for the European country. Between 1846 and 1850, the population of Ireland decreased by 20% to 25%. One million of that was caused by death due to starvation with another one million fleeing to other lands, including Britain and America. A large portion of those were Irish speakers, leading to a decline in the language. The Famine also became a rallying cry for the nationalist movement in Ireland’s eventual independence from Britain. The potato blight was so consequential to Ireland that the population has yet to recover. In fact, the current population is three-fourths of the pre-famine level.
Today, improved crop breeding has allowed potato varieties to become resistant to the HERB-1 strain, with many scientists believing that the strain is now extinct. However, the US-1 strain continues to destroy crops across the globe, causing many scientists to breed new potato varieties. One common breeding technique is genetic modification. However, genetically modified food remains controversial, including in Ireland. Potatoes are the third most consumed crop on the planet and the use of genetically modified potatoes could prevent the use of pesticides and increase potato yields. The newer strains of the blight have become more aggressive as they immediately attack the stems, not the leaves. This has caused farmers to spray fungicides on their crops. Lesser-known countries, such as Belarus, Rwanda, and Uganda, which have been ravaged by the potato blight, cannot afford the sprays. However, without the sprays, the blight could once again gain control and cause crop failures.