|Del Rio, Alfonso|
Submitted to: American Journal of Potato Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/25/2002
Publication Date: 3/15/2003
Citation: Bamberg, J.B., Del Rio, A.H. 2003. Vulnerability of alleles in the US Potato Genebank extrapolated from RAPDS. American Journal of Potato Research. 80:79-85. Interpretive Summary: Potato combines status as a major world crop, high input costs and susceptibility to diseases and pests, high quality demands, and an unusually wide array of closely related wild species that can be crossed with relative ease to the cultivated forms. This situation makes exotic germplasm in potato genebanks very valuable. This value makes the proper preservation of genes an important undertaking for genebank managers. To efficiently use limited resources, we need to study which genes are likely to be vulnerable to loss, and under what conditions. We studied 15 model populations with a genetic structure predisposing them to having rare genes that would be vulnerable to accidental loss during seed regeneration. Although we indeed found some rare and vulnerable genes within individual populations, those same genes always existed commonly (therefore securely) in some other population in the genebank. This work gives us information that helps us efficiently allocate resources for preserving germplasm, so that we can maximize the preservation of genetic diversity with the available funding. These results have great impact on crop genebank manages, and by extension, potato researchers, breeders, farmers and consumers. It is progress in the overall quest to use exotic potato stocks to produce varieties that are more productive, nutritious, and affordable (yet profitable for farmers), while reducing the use of chemicals that threaten the environment and human health.
Technical Abstract: Crop genebanks wish to preserve genes for breeding use, so genebank managers must be concerned with preserving low frequency alleles that are vulnerable to accidental loss from the genebank. Mathematical models and recommendations that follow from hypothetical vulnerable alleles within single populations have been made. This work was undertaken to detect the actual prevalence of such alleles in the US Potato Genebank by extrapolation from RAPD markers. Two outcrossing species were selected, Solanum jamesii Torr. (2n=2x=24) and Solanum sucrense Hawkes (2n=4x=48). RAPD band frequencies at a total of 83 marker loci within each of 15 populations were assessed using 24 plants per population. For both species, about 10 percent of within-populations loci had vulnerable alleles (banded plant frequency less than 40 percent), considering just the particular population in question. However, about half of these were fixed in at least one other population (making that marker invulnerable to loss). The highest within-population banded-plant frequency for loci not fixed in any population was, with one exception, always greater than 40 percent. So, while several alleles may be vulnerable within a given population, these were nearly always fixed or nearly fixed (invulnerable) in another population. This suggests that the safest strategy for maximizing conservation of alleles is to apportion available resources over many separate Mendelian populations, rather than adopt a preservation protocol so rigorous that it can only be practically applied to a limited number of populations.