**3. Application of MAS in breeding for disease resistance in wheat diseases**

Plant diseases are a major constraint in wheat production and significant resources are allocated to control various diseases. The relatively long growing season of winter wheat renders it vulnerable to a range of diseases and breeding for disease resistance is generally thought to be the first line of defence [2]. Disease resistance is generally separated into quantitative and qualitative resistance. Qualitative resistance is most often controlled by a single gene and follows the genefor-gene hypothesis. Thus, an R gene in the host can specifically interact with an *Avr* gene in the pathogen to induce a defence reaction in the host. Qualitative resistance often mediates a complete resistance response, whereas quantitative resistance is regarded as an incomplete or partial resistance. This type of resistance is usually mediated by several minor genes, which are designated as a quantitative trait locus (QTL) [3]. Following the development of MAS, targeted pyramiding of several resistance genes in single lines is now possible. In the following sections, three severe diseases of wheat and correlated resistance genes are described. Common to these diseases is that fungicides are becoming less efficient. Hence, more effective approaches are desired.
