POTATO DIVERSITY IN THE ANDEAN CENTER OF CROP DOMESTICATION

The diversity and population structure of potato landraces (Solanum sp p.) within their center of domestication was studied using isozyme sur veys of four polymorphic loci. The objective in assessing the distribu tion of genetic diversity was to assist in planning conservation strat egies of crop genetic resources that are threatened by genetic erosion . In situ conservation methods depend on this type of analysis. Resear ch was conducted in the region of Cusco, Peru. Eight fields spread amo ng two microregions were randomly sampled, and 610 tubers were studied from this sample. In addition 503 tubers were collected from markets in seven different meso-regions (provinces) surrounding the regional c enter of Cusco. Thirty genotypes were identified in the field sample a nd 82 in the regional sample. The frequency and distribution of genoty pes and alleles are described. A high degree of genotype endemism was found at both the field and regional levels. Genotypes were unevenly d istributed, and most of the genotypic diversity was between rather tha n within populations. At the allele level, however, we found that a ve ry high percentage of the diversity was within rather than between pop ulations. The genotype is the key unit for maintaining the population of potato landraces. Our findings suggest that collections need to be both geographically extensive and intensive. Because farmers are able to maintain most alleles on relatively small portions of their land, i n situ conversation is a viable strategy.