Seedling transplant selection does not cause genetic shifts in Genehank populations of inbred potato species

A basic goal of the U.S. Potato Genebank (USPG) and others is to test assumptions about the stability of genetic diversity in their collections. For example, when heterogeneous seed populations are regenerated, one assumes that using a careful regeneration protocol will result in very little diversity loss in the progeny. However, even the most careful mating scheme cannot prevent genetic selection if it happens earlier-when seedlings are transplanted to become the seed-increase parents. The objective of this work was to assess the prospect of losing diversity at the seedling transplant step. Seeds of a total of 245 original seedlots (from the wild) of 11 inbreeding species [Solanum acaule Bitter, albicans (Ochoa) Ochoa, demissum Lindl., etuberosum Lindl., fendleri A. Gray, polyadenium Greemn., palustre Poepp. ex Schltdl., polytrichon Rydb., papita Rydb., stoloniferum Schltdl. & Bouche, and verrucosum Schltdl.] were sown. The most vigorous, uniform "normal" (N) seedlings were distinguished from any that were small (S) or otherwise would likely be avoided when transplanting the parent plants to be used for seed increase. Bulks of N and S types within seedlots were compared by random amplified polymorphic DNA (RAPD). Genetic similarity (GS) was calculated as average percentage matching band status at RAPD loci. About 25% of the seedlots exhibited S types, but in no case were these significantly different from their N sibs (none with lower than GS = 98%). These results suggest that inbred species' original seedlots are homogeneous and not subject to unwanted seedling selection at transplanting, despite random environmental effects that sometimes produce S seedlings.