Geographical approaches to crop conservation: The partitioning of genetic diversity in andean potatoes

The geographical concepts of spatial scale and the human-geographic region offer significant contributions to the conservation of crop genetic resources. They are used in the present study to examine the partitioning of genetic diversity along two axes: geographical location and landrace population. Locations in the study consist of three micro-regions within the highland Paucartambo region of southern Peru. Six widely distributed landraces of the potato species Solatium stenotomum Juz. et Buk. and S. tuberosum subsp. andigena (Juz. et Buk.) Hawkes are evaluated. Electrophoretic analysis of isozyme loci demonstrates that the majority of allelic variation is contained within the geographical and landrace populations. Geographically, greater than 99% of total variation is found within single micro-regions. Taxonomically, approximately 75% of variation occurs within individual landraces. The weak geographical partitioning of allelic variation is due in part to formerly high rates of seed-tuber exchange. The weak-moderate taxonomic partitioning of variation is attributed to common parentage and shared introgression. Unique genotypes are microgeographically concentrated. Findings recommend that conservation strategies focus on intensive sampling or preservation in micro-regional areas due to the concentration of unique genotypes. Evaluation of the spatial patterning of diversity and recognition of the taxonomic specificity of results (not necessarily applicable even to related potato landraces) rely on biogeographical and human-geographic concepts.