Chromosomal location of a gene for resistance to septoria tritici blotch (Mycosphaerella graminicola)in the hexaploid wheat ’Synthetic 6x’

Septoria tritici blotch, caused by the fungus Mycosphaerella graminicola,is currently the major foliar disease of wheat world-wide, and new sources of resistance and knowledge about the genetics of resistance are needed to improve breeding for resistance to this disease. Sears’s ’Synthetic 6x’ hexaploid wheat, derived from a hybrid of Triticum dicoccoides and Triticum tauschii, was resistant to 12 of 13 isolates of M. graminicola tested. Chromosome 7D of ’Synthetic 6x’ was identified as carrying resistance to all 12 isolates in tests of seedlings of inter-varietal chromosome substitution lines of ’Synthetic 6x’ into ’Chinese Spring’ and to two isolates in tests of adult plants. A septoria tritici blotch resistance gene, named Stb5, was identified using the M. graminicola isolate IPO94269 and mapped on the short arm of chromosome 7D, near the centromere, in a population of single homozygous chromosome-recombinant lines for the 7D chromosome.