Construction of a bacterial artificial chromosome (BAC) library for potatomolecular cytogenetics research

Lack of reliable techniques for chromosome identification is the major obst acle for cytogenetics research in plant species with large numbers of small chromosomes. To promote molecular cytogenetics research of potato (Solanum tuberosum, 2n = 4x = 48) we developed a bacterial artificial chromosome (B AC) library of a diploid potato species S.bulbocastanum. The library consis ts of 23 808 clones with an average insert size of 155 kb, and represents a pproximately 3.7 equivalents to the potato genome. The majority of the clon es in the BAC library generated distinct signals on specific potato chromos omes using fluorescence in situ hybridization (FISH). The hybridization sig nals provide excellent cytological markers to tag individual potato chromos omes. We also demonstrated that the BAC clones can be mapped to specific po sitions on meiotic pachytene chromosomes. The excellent resolution of pachy tene FISH can be used to construct a physical map of potato by mapping mole cular marker-targeted BAC clones on pachytene chromosomes.