Evaluation of Oats for Resistance to Loose Smut. Roy D. Wilcoxson, Professor, Department of Plant Pathology, University of Minnesota, St. Paul 55108. Deon D. Stuthman, Professor, Department of Agronomy and Plant Genetics, University of Minnesota, St. Paul 55108. Plant Dis. 77:818-821. Accepted for publication 21 December 1992. Copyright 1993 The American Phytopathological Society. DOI: 10.1094/PD-77-0818.

The percentage of loose smut (Ustilago avenae) infected plants in oat (Avena sativa) cultivars and breeding lines was determined after kernels were inoculated in a vacuum with water suspensions of teliospores. Fifty-two oat cultivars were evaluated between 1978 and 1990; 14 were resistant, six were moderately resistant, and 32 were susceptible. Many advanced breeding lines were also resistant. Factors that might affect the incidence of smut infection in evaluation trials were studied with cultivars Moore (moderately resistant), Ogle (susceptible), and Starter (resistant). One to three exposures in the vacuum during the inoculation procedure did not greatly affect the incidence of loose smut in the cultivars. As inoculum concentration decreased, the incidence of loose smut decreased, but incidence was not generally affected by storing inoculated seed for 6 wk before planting. In these tests, Starter consistently had the least infection, and Ogle the most; Moore was intermediate. Removal of the lemma and the palea prior to inoculation increased the incidence of smut 10–20%, depending on the cultivar.