Fungal disease causing high losses; especially problematic for potatoes
The fungus starts out by infecting leaves and stems producing gray-green spots that soon turn brown. It spreads by spores that germinate and penetrate cells with a germ tube. Phytophthora is washed into the soil by rainfall where it infests tubers. A single infested tuber is capable of destroying entire plantings.
Phytophthora was introduced to Europe in the middle of the 19th century and gained notoriety as the cause for the Great Irish Potato Famine in 1845. The famine spurred the emigration of two million Irish to America and Australia.
Today, plant breeders and researchers are still occupied with Phytophthora because of its consistent ability to evolve its way around all management strategies used to date.
Genetic engineering is one of the approaches being used to combat Phytophthora. Two genes from a soil bacterium are being used to strengthen natural plant defences.