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

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.