Marker-assisted sampling of the cultivated Andean potato Solanum phureja collection using RAPD markers

The potato crop originated in the Andean highlands where numerous farmer's varieties and non-cultivated wild species exist. An Andean potato collectio n is held in trust at the International Potato Center (CIP) to preserve the biodiversity of this crop and ensure the supply of germplasm for potato im provement worldwide. A core collection representing the biodiversity of the Andean potato germplasm is under construction using morphological, molecul ar, and geographic data. One of the eight cultivated potato species, Solanu m phureja, has been genotyped using the RAPD technique. A protocol suitable for large germplasm collection genotyping has been developed to process nu merous samples at reasonable costs. From 106 RAPD primers evaluated, we hav e selected 12 primers yielding 102 polymorphic markers, which unambiguously discriminated all 128 accessions but 2 that are possible duplicates. The S . phureja germplasm collected throughout the Andean countries appears to ha ve a homogeneous genetic constitution. There was no clear geographic patter n as indicated by cluster analysis of the RAPD data. A sub-group of 20 acce ssions has been identified on the basis of the marker data and selected to maximize molecular (RAPD) variance and polymorphism. The probability of cap turing equal amounts of marker polymorphism in this sub-group of 20 accessi ons by random sampling is less than 40%. This set accessions represents our first group of accessions that may constitute a core of the S. phureja col lection. This tentative core will be challenged for diversity content by al ternate markers and agronomic traits. Hence, the methodology for sampling l ess than 10% of the base collection, proposed for core collections by Brown (1989), can be based on molecular marker data provided cost-efficient fing erprints are developed.