Identification and occurrence of races of Phytophtora parasitica var. nicotianae on dark tobacco

In 1978 isolations of Phytophthora parasitica var. nicotianae were made from black shank-infected plants from Tennessee counties where dark fire- and air-cured tobacco are grown. The race of eight representative isolates were identified with the following differential tobacco cultivars: Madole, DF-300, L8 and A23. Seedlings were grown in the green house in artificial media in 12-unit aluminum muffin pans, each supported by an aluminum cake pan. After 14 days the seedlings were inoculated with mycelium, removed and root system indexed for black shank severity. Reaction of known races 0, 1 and 3 were similar to reactions reported previously. Five of the eight unknown isolates were identified as race 0 and three identified as race 1.