1 INTRODUCTION Host resistance is primarily controlled by qualitative and quantitative genetic mechanisms. Qualitative resistance is imparted by genes with typically major effects on the phenotype, that is, genes that majorly explain the phenotypic variation of a trait of interest (Miedaner & Korzun, 2012). In the context of plant disease, these “major” genes are commonly referred to as resistance or resistance genes (R genes) (Brun et al., 2010; Poland & Rutkoski, 2016).