Teliospore Germination in Puccinia grindeliae, a Rust of the Rangeland Weed Gutierrezia sarothrae. C. M. Liddell, Department of Entomology, Plant Pathology, and Weed Science, New Mexico State University, Las Cruces 88003. C. A. Waddell, and J. P. McEntee. Department of Entomology, Plant Pathology, and Weed Science, New Mexico State University, Las Cruces 88003. Plant Dis. 77:149-152. Accepted for publication 5 October 1992. Copyright 1993 The American Phytopathological Society. DOI: 10.1094/PD-77-0149.

Broom snakeweed, Gutierrezia sarothrae, is a weedy native shrub of the western rangeland. It is difficult and expensive to control by conventional means. Puccinia grindeliae has been identified as a potentially effective biocontrol agent. P. grindeliae is microcyclic in the field. Field-collected teliospores were 37.5–55.0 μm long by 17.5–28.8 μm wide, with a sidewall thickness of 2.5–5.0 μm and an apical wall thickness of 5.0–10.25 μm. The pedicel length of detached spores was 62.5–142.5 μm and pedicel width was 3.8–7.5 μm. Teliospore germination was favored by washing with sterile distilled water and was optimal at 15 C and 98.8% relative humidity. Under these conditions, teliospores germinated in 4–8 hr to form basidiospores, which germinated within 1 hr. Basidiospores produced in the laboratory from field teliospores were 12.5–15.0 μm long by 7.5–11.3 μm wide. Urediniospores from young pustules on plants inoculated to confirm Koch’s postulates were globose and 15.3–27.5 μm in diameter. Mature teliosori formed on plants 4–8 wk after inoculation. These results suggest that germination and infection of the host generally occurs during the evening and early morning hours in the desert Southwest.