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Selection and Evaluation of Three Spring Wheats with Slow-Rusting Resistance to Puccinia graminis f. sp. tritici. B. K. Sally, Research Associate, Department of Plant Pathology, Montana State University, Bozeman MT 59717. E. L. Sharp, Professor, Department of Plant Pathology, Montana State University, Bozeman MT 59717. Plant Dis. 72:413-415. Accepted for publication 8 December 1987. Copyright 1988 The American Phytopathological Society. DOI: 10.1094/PD-72-0413.

Spring wheat plants having susceptible reactions and comparatively low severities when infected with stem rust race 15-TNM were selected from F3 and F4 segregating populations in the field. Succeeding selections in the field were made on the basis of agronomic type and low severity using the slow-rusting cultivar Thatcher as a standard for comparison. Resulting selections were evaluated for latent period in the greenhouse. Three lines were selected having latent periods longer than or similar to that of Thatcher. Under field conditions and with different inoculum levels, the three slow-rusting selections maintained their receptivity and slow-rusting characteristics as measured by areas under the disease progress curve. Differences among the entries were greater under heavy inoculum load, with two selected slow-rusting lines being definitely superior to Thatcher. Significant reductions in thousand kernel weight (TKW) were sustained by both the slow-rusting control and selected lines when subjected to a heavy inoculum load, whereas the fast-rusting control sustained TKW reductions at all inoculum levels.