|Del Rio, A - UNIV OF WISCONSIN|
Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 4, 2005
Publication Date: March 10, 2006
Citation: Bamberg, J.B., Del Rio, A.H. 2006. Seedling transplant selection does not cause genetic shifts in genebank populations of inbred potato species. Crop Science. 46:424-427. Interpretive Summary: Potato is the most important US vegetable, and one of the best hopes for feeding an increasingly hungry world. Breeders need to keep producing better varieties to meet changing needs of the industry and preferences of consumers. Breeders get raw materials from genebanks, so it is in the interest of US Agriculture for the US Potato Genebank at Sturgeon Bay, Wisconsin to maintain the broadest possible array of genes in the collection. We can do so efficiently by determining which genebank activities provide opportunity for genetic losses and which don't. Periodically, seedlots have to be regenerated by growing up seedlings into parent plants which will produce a fresh supply of seeds. When seedlings are transplanted to produce such parents, it seems practical to choose the 'best' most vigorous-looking ones, and discard any extras that are small. We found that excluding these small seedlings makes no significant difference, genetically, so this is one procedure that does not need to be changed.
Technical Abstract: A basic goal of the US 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 drift if genetic selection happens earlier--when seedlings are transplanted to become the seed-increase parents. To assess the prospect of losing diversity at the seedling transplant step, seeds of a total of 276 original seedlots (from the wild) of 8 inbreeding species 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 with RAPDs. Genetic similarity (GS) was calculated as average percent matching band status at RAPD loci. About 1/3 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.