INHERITANCE OF RESISTANCE TO LOOSE SMUT OF OAT

The percentage of plants infected with loose smut (Ustilago avenae) wa s determined in oat (Avena sativa) parental cultivars and lines and in progenies after kernels were inoculated with water suspensions of tel iospores by a vacuum procedure. Inheritance of resistance was studied with F4 populations of three crosses. In cross Ogle/ND 820559 (suscept ible/moderately resistant), the distribution of F4 Progenies appeared bimodal, with more of the progeny clustered around ND 820559 than arou nd Ogle. Twenty-one percent of the F4 lines displayed fewer infected p lants than the resistant parent. In Don/Starter (resistant/resistant), the distribution of F4 lines was skewed toward low incidence of infec tion, with many lines more susceptible than either parent. This sugges ted that resistance was probably conditioned by at least two genes. In Ogle/MN 85230 (susceptible/resistant), the distribution of F4 lines a ppeared multimodal, with many lines similar to MN 85230, the resistant parent. The reaction of F4 lines was verified by testing F5 lines. Re alized heritability, estimated from the Ogle/ND 820559 cross, was 0.93 . The incidence of loose smut in Ogle and ND 820559 was not reduced by reselection.