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Title: How do we address the disconnect between genetic and morphological diversity in germplasm collections

Author
item Jansky, Shelley
item DAWSON, JULIE - University Of Wisconsin
item Spooner, David

Submitted to: American Journal of Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/10/2015
Publication Date: 8/20/2015
Publication URL: http://handle.nal.usda.gov/10113/61520
Citation: Jansky, S.H., Dawson, J., Spooner, D.M. 2015. How do we address the disconnect between genetic and morphological diversity in germplasm collections. American Journal of Botany. 102(8):1213-1215.

Interpretive Summary: Premise of the study: There are over 3000 varieties of indigenous (landrace) potatoes grown by native peoples in the Andes Mountains and in lowland central Chile. They differ in many measures of their form (morphology) by possessing a range of sizes and shapes and colors of both the potato sin on the outside and potato flesh inside. Most of these varieties have been collected and are stored in genebanks worldwide. Many methods have been used to assess the diversity of these collections, and the form and color of the potato tubers has been one of the most important ways to make this assessment. We explored the nature of the diversity of potato landraces by making a simple cross (technically known as an F2 cross) between two potato varieties that possess very little diversity (technically known as highly inbred clones). The result of this single cross was able to produce a range of tuber types that approached the diversity of all of the known tuber types in the Andes Mountains. This result shows that many of the genes producing the great variety of tuber types (as sizes and shapes and colors) reside in very few collections. The result is significant because it questions the use of tuber morphology in estimating the genetic diversity of potato landraces.

Technical Abstract: Morphology has long provided key data to assess diversity in landrace collections in genebanks worldwide. We explored, through an F2 cross between two inbred diploid potato clones, the utility of tuber morphology to assess diversity of potato landraces. We assessed the F2 population created by self-pollinating an F1 clone from a cross between two diploid (2n = 2x = 24) potato clones: DM, a completely homozygous clone derived from somatically doubling an androgenic monoploid of a cultivated potato, and M6, a highly inbred clone derived from seven generations of self-pollination of the wild diploid potato relative Solanum chacoense. We evaluated the F2 population for tuber size, shape and eye depth; skin and flesh colors; and dry matter content. Phenotypic segregation in this F2 population is astonishing. This single cross displayed a range of tuber traits approaching the entire diversity of potato landraces. Morphological characterization of potato used to classify accessions in genebanks is not representative of underlying genetic diversity. This is in agreement with other studies that have shown a lack of correlation between morphological/taxonomic classification and neutral genetic diversity, and a lack of correlation between either morphology or neutral genetic diversity and functional, trait-related genetic diversity in several species. We need better strategies for combining phenotypic and genetic characterization of accessions to develop predictive models that plant breeders can use to identify promising accessions for traits of interest.