Establishment of Microsatellite Assays for Potato Genetic Identification

The in-trust potato collection conserved at CIP has been characterized with a variety of molecular markers to reduce genetic redundancies and identify subsets important for both conservation and crop improvement. We have recently been concerned with developing a potato (Solanum spp.) genetic identification (PGI) kit for curatorial purposes. More than 70 microsatellite markers were tested on a genetically diverse sample of potato germplasm. We have selected a subset of the 18 most informative microsatellites accord-ing to the quality of the DNA products they amplify, their genome location, and the level of polymorphism they detect. These assays have shown that the microsatellites selected are ubiquitous in all seven cultivated potato species. The PGI kit has also been shown to be useful to differentiate potato varieties and cultivars. We have further used this marker set to identify genotype ambiguities in the ex situ germplasm collection. The PGI kit will be routinely used to produce a true-to-type reference for each new entry in our germplasm collection and to attempt to minimize human error in germplasm management. The potato collection held in trust at the International Potato Center (CIP) is mainly composed of cultivated accessions accounting for up to 70 % of the 5,094 clonal and true seed entries (Table 1, after Huamán et al., 1997). Clonal accessions of cultivated potato are maintained in the field at CIP Huancayo and in vitro at La Molina, Peru. Subsets of the collection maintained in vitro are introduced to the field regularly not only to monitor reliabil-ity of conservation procedures but to provide new morphological data or trait evaluation useful to geneticists and breeders. Therefore, the correct identity of each accession maintained in vitro is highly relevant to both curators and breeders at CIP