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Title: GENETIC EQUIVALENCE OF PUTATIVE DUPLICATE GERMPLASM COLLECTIONS HELD AT CIP AND US POTATO GENEBANKS

Author
item DEL RIO, A - UNIV OF WISCONSIN
item Bamberg, John
item HUAMAN, Z - INT'L POTATO CENTER, PERU

Submitted to: American Journal of Potato Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/20/2006
Publication Date: 7/1/2006
Citation: Del Rio, A.H., Bamberg, J.B., Huaman, Z. 2006. Genetic equivalence of putative duplicate germplasm collections held at CIP and US potato genebanks. American Journal of Potato Research. 83:279-285.

Interpretive Summary: Potato breeding programs traditionally benefit from incorporating desirable genetic traits of potato wild relatives into cultivated forms. Hence, keeping the genetic integrity of genebank's collections is important for the success of future breeding since breeders get their materials from genebanks. In order to efficiently preserve and use germplasm, we want the genetics to be stable and predictable in the ways one would assume. We have tested various aspects: Over seed increase? Between in situ and genebank? During seedling transplanting, according to eco-geographical components at site of origin? Now, in this paper at hand, we are testing a similar assumption about stability and predictability: between presumed duplicates in different genebanks. Throughout the years, potato genebanks have incorporated germplasm that was received in the form of progeny of collections that were originally collected and established at other genebanks. So the common assumption is that genebanks hold duplicate materials that should be genetically equivalent. We tested that assumption by comparing presumed duplicate material at the International Potato Center (CIP) and the US Potato Genebank (USPG) and found that most of the time the genetic integrity of these duplicate materials has been efficiently preserved. However, there were a few of them that showed genetic differentiation. DNA analyses suggested that some genetic drift is happening and may be the cause of the ones showing genetic change. Therefore, potato breeders and germplasm users must be aware that although most of the duplicates are identical, there is a small chance that some of the accessions have suffered genetic differentiation as a result of being preserved in two different locations.

Technical Abstract: A common effort among members of the Association of Potato Inter-Genebank Collaborators (APIC) has yielded a global inventory of wild potato genetic resources that is freely available to researches and breeders. In that catalog there are a number of accessions that originated from distributed progeny of a single original germplasm collection. The logical assumption has been that although these samples are allocated in different locations, they should be genetically equivalent. This study tested this hypothesis by comparing 22 pairs of accessions of 18 different potato species, which are reputed duplicates preserved in the potato genebanks of The International Potato Center (CIP) in Peru and of The United States of America (NRSP-6). The RAPD marker analysis revealed that even though the average genetic similarity of reputed duplicates was quite high; there were a few with significant differences. Similarly, SSR markers identified 4 reputed duplicates that were genetically different. The co-dominant expression of SSR markers identified loss of heterozygosity and loss of alleles at some loci for some intergenebank comparisons, a probable indication of genetic drift. The most extreme case was observed between S. berthaultii populations. Therefore, this study reports that duplicate potato collections between CIP and US are in most cases genetically identical but there are a few exceptions.