The book "Molecular Marker Systems in Plant Breeding and Crop Improvement" provides a comprehensive introduction to the application of molecular marker systems in plant breeding and the improvement of crops. It covers fundamental techniques of plant molecular markers, starting from marker localization to gene cloning. The content includes technical approaches to genome analysis, including the comparison of marker systems, position-dependent cloning, and array techniques applied in 19 different crops. A particular focus is placed on the implementation of this knowledge into general and specific breeding strategies, especially concerning biotic stress. The theory and practice of marker-assisted selection for quantitative trait loci (QTL), gene pyramiding, and the future of marker-assisted selection are summarized and discussed for maize, wheat, and soybeans. Additionally, approaches in forestry are presented through examples such as Fagus, Populus, Eucalyptus, Picea, and Abies. The book concludes with a comprehensive overview of relevant patents regarding the use of molecular markers and marker-assisted selection.