PROXIMITY AND INTROGRESSION OF OTHER SPECIES DOES NOT EXPLAIN THE GENETIC DISTINCTION OF NORTHERN SOLANUM VERRUCOSUM POPULATIONS IN MEXICO

Authors: Bamberg, John; DEL RIO, ALFONSO - UNIV OF WI -MADISON

Submitted to: American Journal of Potato Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/1/2007
Publication Date: 8/1/2007
Citation: Bamberg, J.B., Del Rio, A.H. 2007. Proximity and introgression of other species does not explain the genetic distinction of northern solanum verrucosum populations in mexico. American Journal of Potato Research. 84:323-330.

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. One way we can do so is by discovering factors that show where the most diversity exists in the wild. For example, is the pattern of genetic diversity in a species associated with a diversity of locations at which the plants were originally collected in the wild?—altitudes?—environmental characteristics like rainfall and temperature? In previous work, we showed that it is usually difficult to find any such reliable indicators. One exception was the observation that the northern populations of the Mexican species S. verrucosum have unusual genes compared to the more southern populations. But we also noted that the northern and southern groups have different potato species growing nearby. If the apparently unusual genes of the northern group were really just common genes crossed in from other species nearby, the northern verrucosum would not deserve any special attention. We used DNA markers to show that is not the case. S. verrucosum is a species that has some very practical traits like strong disease resistances. So when the genebank distributes samples for evaluation and breeding, or if there is an opportunity for more collecting from the wild, we now know that it will be important to pay special attention to the populations originating in northern Mexico. That will improve our chances of capturing, discovering and incorporating the most useful genes from this wild species into the potato crop.

Technical Abstract: Genebank managers want to determine patterns of diversity in their holdings. In potato, populations of the wild Mexican species S. verrucosum (ver) collected from the north (N) of the natural range had been shown to be genetically distinctive from those in the south (S). But this geographic association with genetic diversity was noted to be confounded with proximity of other wild potato species, suggesting introgression as a possible cause. RAPD bands that distinguished N and S ver were generated. When their association with nearby populations of other species was assessed, the hypothesis of introgression was not supported. We conclude that the distinctive genetics of N ver are probably not common in other proximal species’ populations in the genebank. Thus, N ver germplasm merits special emphasis within ver with regard to collection, preservation and evaluation.