A hundred and fifty years ago in September, 1845, the Dublin local paper “Dublin Evening Post”, reported a “disease in the potato crop”. This turned out to be the potato blight which destroyed 40% of the crop that year and almost 100% the next year. The devatation was known as “The Great Hunger” and resulted in wide spread starvation and mass emigration to Britain and the Americas. As a result, the population declined from @8,295,000 to less then 6,000,000 in a few years.
In 1845 a fungal disease called the late blight, appeared in the Irish potato crop with devastating results. The late blight manifests itself in any part of the plant. Discoloration of the leaves accompainied by downy mildew is sometimes the first sign. The tubers may also be infected in the feild or in storage, with discoloration of the skin, with a reddish brown dry rot extending to the tuber. Later a slimy, foul smelling rot may destroy the tuber.
It is now known that the blight is caused by the fungus Phytophtora infestans an Oomycete which bel;ongs to the family Pythiaceae. This species is characterized by coenocytic mycelium and theproduction of biflagellate, motile zoospores. The fungus is heterothallic and can reproduce sexually in the presence of an opposite mating type. Sexual reproduction follows fertilization of an oogonium by an antheridium resulting in the production of an oospore. Overwintering can be in the form of resting mtcelium or oospores. After germination both will result in the production of sporangia which can germinate directly by means of a germ tube or indirectly by means of the motile zoospores. Germination is followed by encystment and appresorium formation.
Phytohphtora infestans also affected potato crops in the northeast United States and Southern Canada as well as much of western Europe iin addition to Ireland in 1845, but the effects were nowhere near as devestating as in Ireland because in those places the diet was much more diversified and the people were not so dependant on the potato.
Although it happened 150 years ago, the Irish have not forgotten ” The Great Hunger”. Because of the influence of weather on the developement and spread of the late blight, the Irish Meterological Services continues to broadcast warnings of weather favoring the spread of potato blight. Moreover, the Irish people have gained a reputation for contributing personnel and resources in aread of the world currently facing famine, well out of proportion to the size and economy of their small island.