Development of Isogenic Lines for Resistance to Septoria Tritici Blotch in Wheat

Septoria tritici blotch (STB), caused by the fungus Mycosphaerella graminicola (asexual stage: Septoria tritici), is one of the most economically important diseases of wheat worldwide. During the past decade 13 genes for resistance to STB have been identified and several molecular markers have been developed. However, analysis of resistance gene expression and utility for plant improvement programs would be increased if the resistance genes were isolated in a common susceptible background. To address this problem, a program was begun to backcross resistance genes Stb1-8 into two susceptible wheat cultivars. Work with genes Stb2, Stb3, Stb6 and Stb8 has proceeded the farthest. Resistance gene Stb3 is dominant, while Stb2 may be recessive. This will be the first report of recessive resistance to STB if confirmed. Molecular markers linked to the resistance genes are being validated in the backcross progeny and should provide the materials for efficient introgression of these genes into elite germplasm for future wheat improvement.