Diallel analysis of resistance to Stagonospora nodorum in winter triticale

Abstract

Stagonospora (Septoria) nodorum Berk. leaf and glume blotch can cause severe yield losses in triticale (xTriticosecale Wittm.). In diallel crosses the relationship between disease symptoms and grain yield losses were measured and general combining ability (GCA) and specific combining ability (SCA) for disease symptoms on leaves and spikes estimated. Seven parents and their 21 F 1 crosses were grown in micro-plots in two locations as a non-inoculated variant and also artificially inoculated with S. nodorum. Infection caused a mean reduction in kernel weight per spike of 18.1% in the parents and 12.6% in the F 1 crosses, which was mainly a result of a 13.1% and 8.2% reduced 1000-kernel weight, respectively. The number of kernels per spike and the 50-ml weight were little affected. The phenotypic correlations in F 1 crosses between symptom ratings and grain yield traits were low. Heritability was high to very high in parents and F 1 crosses. Both combining ability variances GCA accounted for most of the genetic variation for spike and leaf ratings, indicating predominantly additive gene effects for resistance. The close relationship between parental performance and their GCA effect allows in most cases a prediction of the resistance of F 1 crosses from parental values.