Genetics of Resistance to Septoria Tritici Blotch Disease of Wheat in Cultivar Chamran

Septoria tritici blotch (STB) caused by Mycosphaerella graminicola is one the most important diseases of wheat worldwide. Chamran is a widely cultivated STB-resistant wheat cultivar in Iran but its genetics of resistance to the disease is unknown. To investigate the genetics of resistance of Chamran to STB, the susceptible genotype Darab-2 was crossed with Chamran and F1, F2, F3 and BC1F2 families were prepared. The reaction of progenies derived from direct and reciprocal crosses to an avirulent isolate of the pathogen indicated that the resistance was delivered through nuclear inheritance rather than cytoplasmic inheritance. The heterozygous F1 population displayed a semi-resistant phenotype that was an intermediate between the phenotypes of both homozygous parents. The phenotypic evaluation of F2, F3 and BC1F2 populations indicated that a single incompletely dominant gene in Chamran controls resistance to the studied isolate. The previous results of virulence assays along with molecular experiments performed in this study showed that this resistance gene is an unknown gene.