These oospores may be able to survive for extended periods in the soil or plant debris and give rise to races of the fungus that are resistant to extreme temperatures as well as certain commonly used fungicides. Carroll, Dr. Allen Morehart , professor of mycology, and graduate student Mohamed Sedegui have been identifying the races of the late blight fungus found in Delaware and Morocco. Using a new technique called allozyme analysis to identify the genotype of the fungus, the researchers can quickly let Cooperative Extension personnel know which races of the fungus are present on Delaware farms, and what control measures will work best. Although both mating types A1 and A2 have been found in some areas of North America, there is no evidence of oospores, he adds. But he has discovered that the fungus is surviving at higher temperatures than previously thought possible.
Farmers can no longer depend on a hot summer to wipe out the population of the late blight fungus.
In UD's Fischer Greenhouse Laboratory, Sedegui is running experiments with potato plants and races of the fungus to gather information on exactly how much heat the fungus can stand. After inoculating plants with a late blight fungus, Sedegui places them into growth chambers where he can control the temperature and humidity. Thus he can gather data on the fungus that appears resistant to temperature extremes and at the same time evaluate potato cultivars for resistance to the fungus. He served as chief of inspections to the Plant Protection Service in Casablanca, Morocco. Late blight is of interest to the Moroccan agricultural community because it infects potatoes and tomatoes, which are major food and export crops in that country.