Figure 1

Switchgrass cv. Summer infected with switchgrass rust. Switchgrass cv. Summer plants were inoculated by spraying P. emaculata urediniospores at a concentration of 10⁵ spores per milliliter under controlled conditions. Two weeks after inoculation, dark brown rust pustules containing dikaryotic urediniospores appeared on leaf (a) and stem (b) of switchgrass plants. (c) A switchgrass plant in a field severely infested with rust under natural conditions.