Identification of quantitative trait loci for resistance to Septoria tritici leaf blotch in durum wheat

Septoria tritici blotch (STB), caused by the ascomycete Mycosphaerella graminicola (anamorph Septoria tritici) is an economically important foliar disease in the major wheat-growing areas of the world. In Tunisia, breeding for resistance is an effective way of controlling STB on durum wheat. In this study, resistance to STB in durum wheat was investigated in a population derived from a cross between the susceptible variety Karim and
the newly released variety Salim. One hundred and forty-five single-seed descent derived F6 recombinant inbred lines (RILs) and parental lines were tested for resistance to Septoria under natural infection in field conditions during 2009 and 2010 seasons. Symptoms of STB were assessed by the Double digit 00-99 scoring method at early grain filling stage. A genetic map was constructed using the recombinant population genotyped with a total of 293 DArT markers and 22 SSR markers. Linkage analysis defined 29 linkage groups with a total map length of 795 cM. Most markers were mapped to the B-genome with length of 450 cM against 345 cM to the A-genome. A QTL for resistance to STB was identified and located on chromosome 3B. This QTL showed significant effect in 2009 and 2010 seasons with R2 value of 23,47%. DArT markers linked to the QTL influencing resistance to STB have potential use in durum wheat breeding programs.