Inheritance of Septoria tritici blotch resistance in winter wheat

Septoria tritici blotch (STB), a fungal foliar disease of wheat (Triticum aestivum L.) caused by Septoria tritici Rob. ex Desm., is a major constraint to wheat production worldwide. Understanding the inheritance of resistance in known resistant genotypes would potentially lead to more efficient deployment of host plant resistance. In our study, inheritance of seedling STB resistance was evaluated by an eight-parent full diallel set of crosses. Parents, F₁, and reciprocal F₁ were planted in a greenhouse on three different dates. Within each planting date, three to five seeds of each entry were planted in a randomized complete block design with three replicates. Plants at the second-leaf stage were inoculated with a bulk of six S. tritici isolates. Significant general combining ability (GCA), specific combining ability (SCA), and reciprocal effects were observed in the analysis of variance. The ratio of GCA sum of squares relative to SCA sum of squares suggested that GCA was more important than SCA. Additive gene effects played a major role in host response to STB, while nonadditive gene effects were also detected. General combining ability effects of individual genotypes were in a close agreement with parental performance. 'KS94U338', a genotype with putative resistance derived from Aegilops tauschii Coss., had the lowest STB score and the highest general combining ability. Our results suggested that KS94U338, which possesses resistance thought to be distinct from other known sources, should prove useful in breeding efforts to improve STB resistance in wheat.