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Relative Nuclear DNA Content of Rust Fungi Estimated by Flow Cytometry of Propidium Iodide-Stained Pycniospores. Tamar Eilam, research associate, Department of Botany, Tel Aviv University, Ramat Aviv, 69978, Israel; W. R. Bushnell(2), and Y. Anikster(3). (2)research plant physiologist, USDA-Agricultural Research Service, Cereal Rust Laboratory, University of Minnesota, St. Paul 55108; (3)associate professor, Department of Botany, Tel Aviv University, Ramat Aviv, 69978, Israel. Phytopathology 84:728-735. Accepted for publication 10 March 1994. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1994. DOI: 10.1094/Phyto-84-728.

Flow cytometry was used to estimate the relative nuclear DNA content of pycniospores from 85 collections of 13 species of rust fungi. For a given sample, 10,240 fluorescent events were measured. Sufficient pycniospores could be obtained from as little as one well-developed pycnial cluster. Numbers of fluorescent events plotted against intensity of fluorescence usually exhibited a single well-defined peak with coefficients of variation of 10% or less. Results confirmed and extended data for small numbers of basidiospores obtained earlier with the microscope photometer. DNA content relative to that of a Puccinia hordei standard was estimated to be as follows (in order of increasing DNA content): P. lagenophorae, 53%; P. graminis, 56%; P. coronata, 64%; P. sorghi, 84%; P. hordei, 101%; P. recondita, 105%; Uromyces hippomarathricola, 107%; U. reichertii, 120%; Tranzschelia pruni-spinosae, 150%; P. allii, 164%; P. helianthi, 185%; U. vignae, 336%; and U. appendiculatus, 346%. Within P. hordei, collections from Hordeum bulbosum had higher DNA content than collections from other telial host species; within P. recondita, collections from each of four telial host species differed, suggesting that these fungi are diverging genetically on some telial host species.