Unbalanced Bulk of Parents’ Seed does not Cause Significant Drift in Germplasm Regeneration of Two Model Potato (Solanum) Species Populations

Abstract

Although the potato of commerce, the autotetraploid Solanum tuberosum is a clonal crop, genebank maintenance of wild and cultivated relatives is commonly done as populations of true seeds. In order to help equalize gamete contribution and prevent genetic drift over seed regenerations, an equal number of seeds from each mother plant may be bulked as a source of parents for future regenerations. To determine if this extra sample is beneficial, we selected two S. andigena populations with great variation of seed production among mother plants. Seed production of each mother plant was recorded over 12 standard seed regenerations and genetic indicators were developed in the form of 105 polymorphic RAPD bands. For each polymorphic band, the variation of seed production among mother plants was used to estimate the potential impact on band phenotypic frequency due to an over-all seed bulk. Most bands were fixed or nearly fixed within at least one of the populations, such that the variation in maternal seedset observed would not have put them at signficant risk of being lost in an over-all bulk. For balanced bulks to provide a significant preservation advantage, a band must be rare in all populations and associated with mother plants that produce significantly fewer seeds. Of over 100 loci assessed here, none met these conditions. We therefore conclude that the duplication of documentation and storage space invested in making balanced seed bulks probably return little genetic benefit to the genebank.