Plant toxins: Many millions of people have died over the centuries as a result of plant diseases - not least those who perished during the Great Famine, which ranks among the worst tragedies of its kind in recent history.
Plant diseases have caused misery and death since the dawn of agriculture, with people having little or no idea what caused these deaths, explained Dr Paul Nicholson, of the John Innes Centre in Norwich.
He was speaking at the BA festival yesterday in a session titled "Famine to feast: the good guys and the bad guys". The festival ends today.
A simple fungus drove the Famine and the loss of an essential food source produced a death toll of at least one million people over five years. "That wasn't entirely due to the fungus. The British government and the landowners were also involved," Dr Nicholson said.
Many deaths have also been caused by rusts and other diseases, particularly of grain, he said. Diseases including fusarium rusts and fungal grain infections, known as ergots, leave highly-dangerous toxins on the grain and these go on to poison those who eat the wheat, rye or barley which carries them, he said.
"The Romans described rusts as a huge destroyer of crops," Dr Nicholson said. They introduced a rust-related festival called Robigalia, in which they sacrificed a red dog to appease the gods and keep rusts at bay.
Ergots may have been associated with the Salem witch trials of 1692, he added. Some forms of ergots can cause convulsions before death and there is speculation that supposed spells, cast by witches, which induced convulsive death, were actually a result of ergots.
Prof Allan Downie described the "good guys" - plant infections by bacteria which allow legumes to fix their own nitrogen fertiliser from the atmosphere. The goal is to find ways to allow other plants to fix nitrogen. This would deliver huge savings and reduce environmental impacts.
