Clonal Differentiation and Identification of Polyploids in Juglans Hybrids

Juglans is a genus of ca. 20 species divided into four sections (Rhysocaryon, Cardiocaryon, Trachycaryon and Juglans) with a broad geographic distribution which is known for producing edible nuts and high-quality wood. Hybrid Juglans trees are becoming increasingly popular for forestry purposes in Europe because of their fast growth and adaptability. In this work, DNA was isolated from leaves of eighty-five individuals of Juglans species and hybrids and evaluated at eight nSSR and seven EST-SSR markers. The markers were able to differentiate all trees on an individual basis, and further, gave indications of polyploidy in some samples. Consequently, fifty-nine samples were then checked for ploidy by flow cytometry. Genetic structure of the population was evaluated with the most probable number of groups being K=3, which agrees with the four sections of the genus Juglans, where Cardiocaryon and Trachycaryon are genetically very similar and thus comprise one group. These results agree with other research using SSRs in Juglans. Flow cytometry revealed thirteen triploid individuals, where twelve are in agreement with the marker study, one was only detected by flow cytometry.