Starch Characteristics of Modern and Heirloom Potato Cultivars

In a number of ways, modern potato breeding efforts differ from those that created heirloom cultivars. As a result of the rapid expansion of the potato processing industry in the mid twentieth century, potato breeders shifted their focus from fresh market varieties to those intended for the fry and chip markets. Selection for higher dry matter content and lower reducing sugar levels in tubers was successful. This study sought to determine whether modern processing cultivars differ from heirloom cultivars for two major characteristics of tuber starch, amylose content and starch granule morphology. Since breeding efforts for processing potatoes have focused on the maintenance of tuber quality during storage, these parameters were measured in both fresh and stored tubers. Twenty cultivars selected to span the range of cultivar release dates in the U.S. were grown at Hancock, WI in 2009 and 2010 and evaluated for tuber amylose content and measurements of starch granule surface area, length, width, length to width ratio, and smoothness. These traits were found to be stable across years and during storage. Significant differences in the amylose content and starch granule morphology exist among cultivars, but there is no clear distinction between modern and heirloom cultivars. Genetic variation for amylose content and starch granule morphology was found within the set of clones sampled for this study. However, germplasm with higher amylose content will need to be identified and utilized in breeding if the nutritional benefits associated with high fiber and low glycemic index are to be realized.