<P> In Ireland, the expansion of potato cultivation was due entirely to the landless labourers, renting tiny plots from landowners who were interested only in raising cattle or in producing grain for market . A single acre of potatoes and the milk of a single cow was enough to feed a whole Irish family a monotonous but nutritionally adequate diet for a healthy, vigorous (and desperately poor) rural population . Often even poor families grew enough extra potatoes to feed a pig that they could sell for cash . </P> <P> A lack of genetic diversity from the low number of varieties left the crop vulnerable to disease . In the early 1800s, a strain of potato blight (Phytophthora infestans) known as HERB - 1 began to spread in the Americas, especially Central and North America destroying many crops . The blight spread to Europe in the 1840s where, because of an extreme lack of genetic diversity, the potato crops were even more susceptible . In Northern Europe there were major crop losses lasting throughout the rest of the 19th century . Ireland in particular, because of the extreme dependence of the poor, especially western Ireland, on this single staple crop, was devastated by the blight's arrival in 1845 . </P> <P> The Lumper potato, widely cultivated in western and southern Ireland before and during the Great Famine, was bland, wet and poorly resistant to the potato blight, but yielded large crops and usually provided adequate calories for peasants and labourers . Heavy dependence on this potato led to disaster when the blight quickly turned harvest - ready and newly harvested potatoes into a putrid mush . The Irish Famine in the western and southern parts of Ireland between 1845--49 was a catastrophic failure in the food supply that led to approximately a million deaths from famine and (especially) diseases that attacked weakened bodies, and to massive emigration to Britain, the U.S., Canada and elsewhere . During the famine years roughly one million Irish emigrated; this tide was not turned until the 20th century, when Ireland's population stood at less than half of the pre-famine level of 8 million . </P> <P> It is generally believed that potatoes entered Africa with colonists, who consumed them as a vegetable rather than as a staple starch . Shipping records from 1567 show that the first place outside of Central and South America where potatoes were grown were the Canary Islands . As in other continents, despite its advantages as an anti-famine, high - elevation alternative to grain, potatoes were first resisted by local farmers who believed they were poisonous . Colonialists also promoted them as a low cost food and so it was a symbol of domination . In former European colonies of Africa, potatoes were initially consumed only occasionally, but increased production made them a staple in certain areas . Potatoes tended to become more popular in wartime due to their being able to be stored in the ground . It was well established as a crop by the mid-20th century and in present - day Africa they have become a vegetable or co-staple crop . </P>

Where did potatoes go during the columbian exchange