Selecting a Solanum tuberosum subsp andigena core collection using morphological, geographical disease and pest descriptors

One of the largest and most diverse clonally propagated potato collections of cultivated potato species is maintained at the International Potato Cent er (CIP). Almost 75% of this collection is S. tuberosum subsp. andigena (he reafter andigena) cultivars. The first step to select a core collection of this subspecies was to identify duplicate accessions of the same cultivar u sing comparisons of morphological characters and electrophoretic banding pa tterns of total proteins and esterases. This reduced the number of accessio ns in the collection from 10,722 to 2,379. The number of accessions of the same cultivar in the original collection ranged from 1 to 276. This is a re port on the selection of a core from the 2,379 morphologically different cu ltivars using morphological, geographical, and evaluation data. A total of 25 morphological descriptors were scored from all 2,379 andigena cultivars. A phenogram was constructed from these data using a simple matching coeffi cient and the unweighted pair group method using arithmetic averages. We de cided to include in the core a proportional sample consisting of approximat ely the square root of the number of accessions from each first geographica l division (state, department, or province) of countries where andigena was collected. Accessions mere chosen first to represent the widest morphologi cal diversity and to maximize geographical representation of the clusters d istributed on the main branches of the morphological phenogram. Second, the representative accession of each cluster was also chosen considering data on resistance to diseases and pests, dry matter content, and number of dupl icate accessions identified in the original collection. The resulting core has 306 accessions (12.86%) hom eight countries from Mexico to Argentina. T he full breeding potential of Andean farmer-selected potato cultivars that have been maintained for centuries in their center of diversity remains unk nown. A thorough evaluation of their reaction to diseases and pests and oth er desirable traits is now feasible because the selected andigena core set covers the broadest genetic base that is available in ex situ conservation.