Development and applications of a set of chromosome-specific cytogenetic DNA markers in potato

Reliable and easy to use techniques for chromosome identification are critical for many aspects of cytogenetic research. Unfortunately, such techniques are not available in many plant species, especially those with a large number of small chromosomes. Here we demonstrate that fluorescence in situ hybridization (FISH) signals derived from bacterial artificial chromosomes (BACs) can be used as chromosome-specific cytogenetic DNA markers for chromosome identification in potato. We screened a potato BAC library using genetically mapped restriction fragment length polymorphism markers as probes. The identified BAC clones were then labeled as probes for FISH analysis. A set of 12 chromosome-specific BAC clones were isolated and the FISH signals derived from these BAC clones serve as convenient and reliable cytological markers for potato chromosome identification. We mapped the 5S rRNA genes, the 45S rRNA genes, and a potato late blight resistance gene to three specific potato chromosomes using the chromosome-specific BAC clones.