|Del Rio, Alfonso|
Submitted to: American Journal of Potato Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/11/2006
Publication Date: 11/1/2006
Citation: Bamberg, J.B., Fernandez, C.J., Del Rio, A. 2006. A new wild potato mutant in Solanum stoloniferum Schltdl. lacking purple pigment. American Journal of Potato Research. 83:437-445. 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 conduct studies that will help germplasm workers better understand the basic genetics of stocks in the genebank. As a result of collecting wild potatoes in southern Arizona, we discovered a very unusual plant lacking purple pigmentation, which we called “P-less”. This plant became an important tool to use in crosses that revealed that the genetics for P-less is actually present, in hidden form, in wild potato populations from many origin sites across the US and Mexico. This P-less trait can be assessed very easily—even in small seedlings it is quite clear which have purple under the leaves and on the stem and which do not. So this trait could be used to study the movement of genes between populations in the wild, preferences of pollinators, and other basic questions related to the genetics of this group of potato species. All these types of information will add to our knowledge of how to best to collect and preserve such stocks in the genebank, and will give researchers and breeders insights into how to more efficiently manipulate their genetics to incorporate their useful traits into the potato crop.
Technical Abstract: A sample of S. stoloniferum (previously taxon S. fendleri), PI 620874, was collected by the authors from a previously undocumented site in the Patagonia Mountains of southern Arizona in September 2001. When original seed was grown at the US Potato Genebank, two of 25 seedlings produced white flowers, and upon closer inspection were found to be completely without purple pigmentation on the tubers, stems and underside of leaves-- a characteristic previously unknown in this species and rare in wild potato overall. S. stoloniferum, like other species of series Longipedicellata (LON) are disomic tetraploids. Results of crossing trials were consistent with the most simple genetic explanation for this phenotype: a recessive p allele at the P locus, making the mutant (pp pp), or "P-less". P-less plants were testcrossed with over 100 other LON populations originating across the US and Mexico to make BC1 generations that had either 1/2 or 1/4 P-less seedlings. Surprisingly, about one-third of the populations, and from widely distributed origins, produced 1/2 P-less progeny, indicating that they also possess the recessive p allele on one genome (PP pp). This discovery of the p allele in LON and P-less mutants could provide a simple, unambiguous seedling marker for study of geneflow and dispersion, pollinator behavior in the wild, gene expression interactions between homeologous genomes, and chromosome pairing control.