Foot rot in winter rye (Secale cereale L.) caused by Pseudocercosporella herpotrichoides, Fusarium spp., and Microdochium nivale (syn Fusarium nivale) can be controlled best by host resistance. In this study, the inheritance of foot rot resistance was examined using 15 diallel and 11 factorial crosses tested along with their parent inbred lines. Four out of six test environments in southern Germany were artificially inoculated with either P. herpotrichoides, F. culmorum, or M. nivale. In the other two environments, naturally occurring field epidemics were used. At milk ripening, 50 stems per plot were rated individually for foot rot on a 1 to 9 scale. Significant estimates of genotypic variance and high heritabilities (h(2) = 0.82-0.92) were observed in all genetic materials, General combining ability (GCA) was the main source of genetic variation among crosses, while specific combining ability was negligible. Considerable environmental effects and significant genotype x environment interactions were found. Strong phenotypic correlations (r approximate to 0.9) existed between line per se performance and GCA effects. Heterosis was not important. For optimizing disease assessment, h(2) was estimated for varying numbers of stems, environments, and replicates. For inbred lines tested in two environments with two replicates or for single crosses tested in four environments with two replicates, a sample size of 15 plants per plot should result in a h(2) of about 0.7. In conclusion, substantial progress can be expected from selection for foot rot resistance in hybrid rye on the basis of line per se performance by rating unspecific foot rot lesions.
