First Report of Rust Caused by Puccinia recondita on Smooth Bromegrass. K. E. Zeiders and R. T. Sherwood, USDA-ARS, U. S. Regional Pasture Research Laboratory, University Park, PA 16802. Plant Disease 70:801, 1986. Accepted for publication 11 March 1986. Copyright 1986 The American Phytopathological Society. DOI: 10.1094/PD-70-801b.
A rust disease was observed on leaves and culms of smooth bromegrass (Bromus inermis Leyss.) from late July through November 1985 in a seed production nursery at the Pennsylvania Agricultural Experiment Station located near State College. The disease was also found in three fields within 16 km of the nursery. The uredinial stage of the rust was moderate to severe in mid-August, occurring mostly on leaves. Uredinia were orange-brown, round to elongated, up to 0.8 mm long, and amphigenous. Urediniospores were orange-brown, one-celled, spherical to oval, slightly echinulate, with six to eight scattered germ pores, and 28–36 × 20–30 μm in size. Dark gray-brown telia on the regrowth leaves were not found until 19 November. Teliospores were orange-brown, two-celled, oblong-clavate, with the apical cell wall 5 μm thick at the tip, and 45–52 μm long × 11–13 μm wide. On the basis of our observations, the fungus on smooth bromegrass belongs in the Puccinia recondita Rob. ex Desm. group. In a host-range inoculation test in the greenhouse, only smooth bromegrass became infected by P. recondita; eight other forage grasses showed no symptoms. The outbreak of rust reported here is significant because P. recondita has not been reported previously on this important crop.