Accumulation of Genetic Diversity in the US Potato Genebank

Abstract

Efficient assessment of genetic diversity in a potato genebank includes understanding how much of the available genetic diversity has been captured in the genebank (from the wild or from other ex situ sources). We used existing datasets from three of the genebank’s 93 species to model the increase of diversity over time, as measured by the addition of AFLP bands. DNA samples of a total of 411 populations of S. microdontum (mcd), S. jamesii (jam), and S. fendleri (fen) were analyzed. Assuming the first (oldest) populations as the baseline, the number of AFLP markers have increased by 128 % (mcd), 154 % (jam) and 111 % (fen) with addition of populations to the genebank. The pattern of actual observed chronological gain in diversity was similar to that which one would expect from random additions of populations except for fen, suggesting recent additions were somewhat redundant. All species continued to accumulate new loci at least up to 100 populations, jam particularly so. Much effort has been made over many years to thoroughly collect jam, so its 125 populations could serve as a model for the number of samples one might practically hope to acquire for the average species. Since 100 jam populations captured 95 % of its polymorphic loci, 100 populations might be set as an optimal benchmark. The average species in the genebank now has about 54 populations, so the size of the genebank would need to roughly double its capacity to optimize diversity according to the jam model. That would be a challenge, but probably not as limiting as the great time and resources needed to collect the germplasm.