Chloroplast DNA analysis in oak stands (<em>Quercus robur</em> L.) in North Rhine-Westphalia with presumably Slavonian origin: Is there an association between geographic origin and bud phenology?

Abstract

Slavonian oaks (Quercus robur subsp. slavonica) have been introduced into Germany in the second half of the 19th century from the lowlands of the rivers Save and Drava in today’s Croatia. If compared to indigenous oak stands, they are characterized by good growth, comparatively low seed production and a late bud burst. Based on the information of European-wide variation patterns at chloroplast DNA markers in oaks we adapted chloroplast microsatellites for the analysis of all oak stands of presumably Slavonian origin in the Münsterland and lower Rhine regions. We were able to distinguish between Slavonian haplotypes with no natural occurrence in the study area and indigenous types that do not occur in the Balkan region. A generally high differentiation among stands was observed at chloroplast markers (GST = 0.674). Based on the haplotype information and historic records we found that stands with Slavonian material have been established between the years 1878 and 1903. In a total of 910 analysed trees the Slavonian haplotypes 5, 2 or 17 were the most frequent ones but a considerable amount of samples with indigenous haplotype 1 or haplotype10 with presumed origin in Southwestern Europe was also present. A clear association between haplotype 2 and late bud burst was detected in adult stands and in a field trial established with seeds from Slavonian and indigenous oak stands. The information about the haplotype composition in all Slavonian stands can be used as reference for the certification of reproductive material. The analysis of cpDNA haploytpes in old oak stands that had been established before the introduction of foreign seed material can give valuable information for the identification of indigenous oak stands.