Exploring the Genetic Diversity of Wild Cranberry Populations in the Upper Midwestern United States

ABSTRACT Plant breeding continuously evolves to satisfy the needs of the growing population, but in many crops, it has resulted in a decline in the genetic diversity available. Therefore, increasing knowledge of the range, genetic relationships, and diversity among crop wild relatives (CWR) is essential for the efficient use of available germplasm in breeding programs. In cranberries (Vaccinium macrocarpon Ait.), most cultivars share the same genetic background based on only a few wild selections. This limits the breeding pool for selection to support the cranberry industry. Therefore, we studied 36 wild populations of V. macrocarpon and V. oxycoccos L. across Wisconsin and Minnesota using 32 simple sequence repeat (SSR) markers. We found high levels of heterozygosity in both species, despite previous molecular markers studies revealing low genetic variation. In V. macrocarpon, a total of 294 alleles and moderate to high levels of heterozygosity (observed [HO] = 0.51, total [HT] = 0.66) were found. As expected for outcrossed polyploid species (4x), higher levels of heterozygosity (HO = 0.81, HT = 0.83) were found in V. oxycoccos than in V. macrocarpon. A comparison between wild V. macrocarpon with a group of cultivated and experimental hybrids found a distinct separation between both groups, suggesting there is diversity in the wild that needs to be explored and incorporated into breeding programs. The results of our studies are the first to explore in depth the genetic diversity of wild cranberry populations in the upper midwestern United States and provide novel information to support in situ conservation efforts to protect CWR of one of the few North American native crops.