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Cytology and Histology

Postpenetration Phenomena in Wheat Cultivars with Low Receptivity to Infection by Puccinia graminis f. sp. tritici. Dereje Ashagari, Head, Plant Pathology Section, Crop Protection Division, State Farms Development Authority, P. O. Box 5767, Addis Ababa, Ethiopia; J. B. Rowell, research plant pathologist, Cereal Rust Laboratory, Agricultural Research, Science and Education Administration, U.S. Department of Agriculture, University of Minnesota, St. Paul 55108. Phytopathology 70:624-627. Accepted for publication 7 December 1979. 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, 1980. DOI: 10.1094/Phyto-70-624.

The characteristic low receptivity of wheat (Triticum aestivum) cultivars Marquis, Lee, Thatcher, and Idaed 59 to infection by Puccinia graminis f. sp. tritici, as shown by number of uredia in adult plants, was constant under different environments and with several cultures of diverse races identified as virulent on seedlings of these cultivars. Fungal penetrants of putative virulent cultures interacted either compatibly or incompatibly in all cultivars with low receptivity. Compatible colonies in cultivars with low receptivity were significantly smaller than those in plants of highly receptive cultivars Purdue 5481CI and Baart. In Lee, Thatcher, and Idaed 59 the proportion of compatible to total penetrants reflected the reduced number of uredia produced on these hosts. In Marquis, however, the proportion of compatible penetrants did not differ significantly from that in Purdue 5481CI. The reduced colony size of compatible penetrants observed histologically at 65 and 96 hr in all hosts with low receptivity was generally reflected by the smaller uredia that appeared later. Highly incompatible colonies in cultivars with low receptivity were smaller than compatible ones and were associated with collapsed host cells. Thus, these incompatible penetrants produced a hypersensitive response similar to that associated with specific gene resistance and presumably failed to produce uredia.