Efficacy and mapping of resistance to Mycosphaerella graminicola in wheat

Wheat is the most important food and feed crop, contributing about 19% of the required human dietary energy. The annual growth rate of the global cereal production -including wheat- is below one per cent. This is due to biotic and biotic constraints – including diseases – such that production falls short of meeting future food demands. Thus more wheat should be produced and the best way to achieve that is to produce and release cultivars with better disease resistance. Septoria tritici blotch (STB) is Europe’s major foliar wheat disease and is caused by the fungus Mycosphaerella graminicola that reduces yields to at least 50% under conducive conditions. STB management relies mostly on chemical control, but the continuously increasing incidence of fungicide resistant strains in fungal populations has resulted in a growing awareness of the importance of host resistance. However, the number of identified resistance genes to STB is very low compared to the number of known resistance genes for other wheat diseases. Moreover, these genes are not very effective and therefore of limited practical value. The aim of this research was to discover new genes for resistance and to develop tools facilitating their deployment in modern breeding programs. Three new resistance genes were detected on chromosomes 3DL, 5AL and 6DS that were designated as Stb16, Stb17 and Stb18, respectively. Stb17 was only expressed in adult plants, which is new for this disease, Stb18 is effective to a limited suite of isolates, but Stb16 has an extremely broad resistance that is of great interest to the commercial breeding industry. However, the impact of an individual gene depends strongly of the genetic make-up of a cultivar. Along with improved testing protocols these results are important for the successful commercial deployment of Stb genes in European wheat breeding programs.