Genetics and QTL Mapping of Septoria Tritici Blotch Resistance in Spring Wheat.

Genetics and QTL Mapping of Septoria Tritici Blotch Resistance in Spring Wheat

   Septoria tritici blotch (STB) caused by ascomycete fungus Mycosphaerella graminicola (Fückel) J. Schröt. (anamorph: Septoria tritici Desm.), is one of the important foliar diseases in wheat (Triticum aestivum L.) growing areas, with high temperature and humidity. The disease gained more importance due to the formation of leaf spotting complex in field with other leaf spot diseases like tan spot and septoria nodorum blotch, resulting in considerable yield reduction. In order to study the genetics and to identify the QTL responsible for STB, a mapping population consisting of 138 F_2-8 recombinant inbred lines (RILs) derived from a cross between the susceptible cultivar ‘Steele-ND’ and a resistant line ND 735, was inoculated with M. graminicola isolate Ma04-9-4 and evaluated in three greenhouse experiments. A framework linkage map consisting of a total of 392 markers of both diversity array technology (DArT) and simple sequence repeat (SSR) markers was constructed. The framework map spanned a total distance of 1789.3 cM and consisted of 17 linkage groups. The framework linkage map and phenotypic data was used to map the QTL for STB. A total of four QTL (one each on 1D, 3A, 5B and 7B) were detected through composite interval mapping (CIM). Among these four QTL detected, a QTL on 5B explaining 14% of the phenotypic variation, was consistently mapped across all experiments and in individual experiment. Additional QTL discovery may be possible in the D genome. If validated, the identified QTL may be useful in marker assisted selection for STB.