Rapid Identification of Rust Resistance Genes Through Cultivar-Specific De Novo Chromosome Assemblies

"Map-based cloning" is a frequently used approach to isolate rust resistance genes. A critical step during map-based cloning is the transition from genetic information, i.e., a genetic map, to physical sequence information. Bacterial artificial chromosome clones are often used to establish sequence information spanning a genetic interval. However, a major limitation of BAC clones consists in their small insert size of 100-200 kb. Targeted chromosome-based cloning via long-range assembly (TACCA) is a method that can replace BAC library screening. This approach involves chromosome flow-sorting and the establishment of a long-range de novo assembly. This chapter provides an overview of TACCA as well as a detailed description of sequence analyses, molecular marker development, and candidate gene identification.