Virulence variability of Ethiopian Zymoseptoria tritici isolates and efficacy of wheat genotypes and Stb resistance genes against the isolates

Septoria tritici blotch caused by the fungus Zymoseptoria tritici is a serious threat to wheat production worldwide. Knowledge of physiologic specialization of the pathogen and identification of potential source of resistance are prerequisite for designing durable management strategies. The present study was targeted to determine the virulence pattern of eight bread wheat derived Ethiopian Z. tritici isolates, and efficacy of known Stb resistance genes and wheat genotypes against the isolates. Disease severity analysis confirmed the presence of specific interaction in the pathogen. Pathogenecity assay identified 60 isolate-specific resistances among all (n = 360) interactions. Of 45 wheat genotypes, 40% showed no isolate-specific resistance responses and were susceptible to all isolates. Tested Z. tritici isolates showed significantly different virulence patterns with virulence on 71% to 93% wheat genotypes. Isolate I1 was found to be the most virulent (on 93% of the tested genotypes), and hence, useful for germplasm screening. Among tested known Stb genes, Stb13/Stb14 in Salamouni did not confer resistance to any of the isolates, while Stb16 in KM7 conferred broad spectrum resistance to 75% of them, and thus, promising source of resistance to STB in Ethiopia. Among tested 20 commercial cultivars, 45% did not confer resistance to all the isolates. Three genotypes (MURGA, Km7 and the cultivar Hidase) conferred the greatest level of resistance to the tested Ethiopian Zymoseptoria tritici isolates. The information is very useful for wheat breeders and the wheat farming community in making informed decisions to manage STB disease in Ethiopia.