Specific resistance in wheat genotypes to leaf blotch (Zymoseptoria tritici)

In the world, including Ethiopia, wheat leaf blotch is one of the most important diseases. Knowing the source of resistance in wheat genotypes is very important for developing varieties, pathogen variability studies, and taking management action. However, in Ethiopia, the study of gene-for-gene or minor gene-for-minor gene interactions and wheat genotype reactions are very limited. Therefore, this study aimed to answer these research gaps. Fifty-four genotypes and one differential line were evaluated against six pathotypes. The 330 treatment combinations with three replications were set up in a completely randomized factorial layout in the greenhouse. The host-pathogen interaction and seedling resistance were identified using the least significant difference method. At a 95% similarity level, the average linkage hierarchical clustering method and euclidean distance were used to classify the cultivars. Resistance assay detected 152 wheat-Z. tritici interactions (16 pathotype-specific resistances, 70 broad-spectrum resistances, and 66 susceptible), and 178 non-wheat-Z. tritici interactions, among all (n = 330) interactions. Genotypes like 21Eeit (046), 21Eeit (027), 41ESWYT (046), and the rest of the thirteen showed resistance to one pathotype (pathotype-specific or minor gene-for-minor gene interactions or vertical resistance). 54ISBWSN (018) and 54ISBWSN (113) indicated resistance reactions to six and five pathotypes, respectively. About 23 (42%) genotypes showed resistance reactions to more than two pathotypes, known as broad resistance. Differential line ESTANZUELA FEDERAL carrying the Lb7 gene was infective against five pathotypes and intermediate against one pathotype. Cluster analysis identified 25 groups based on the similarity of mean disease severity and suggested 45.4% resistance variability of wheat genotypes. The resistant genotypes identified are very important for further breeding.