Assignment of frost tolerant coast redwood trees of unknown origin to populations within their natural range using nuclear and chloroplast microsatellite genetic markers

Abstract

Considering climate change and expected changes in temperature and precipitation, some introduced timber species are prospective for growing in Germany or Europe to produce valuable wood products and support sustainable forestry. The Californian tree, coast redwood (Sequoia sempervirens [D. Don] Endl.) is one of such species due to its excellent wood properties and high growth rate. It is sensitive to the freezing temperatures, but several trees of unknown origin introduced to Germany decades ago demonstrated high frost tolerance, and their propagated cuttings were planted all over German botanic gardens and arboreta. The knowledge of their origin within the natural distribution range could help us identify the potential genetic resources of frost resistant coast redwood genotypes. Therefore, both trees of unknown origin in Germany (G) and two reference data sets representing the \"Kuser provenance test\" established in 1990 in France (F) and samples collected in California (C) with known origin were genotyped using 18 microsatellite markers including 12 nuclear and six chloroplast simple sequence repeat (cpSSR) markers. The number of haplotypes found in the data sets based on six cpSSR markers was surprisingly very high. These markers were used to assign the German frost resistant trees (G) to the two reference data sets (F and C). The genetic structure among California samples (C) based on nSSR and cpSSR markers was very weak and mainly due to northern and southern clusters separated by the San Francisco Bay as a geographic barrier between coast redwood populations confirming previously published data. It was impossible to confidently assign frost tolerant trees (G) to single native populations, but rather to either the northern or southern cluster. However, the existing frost tolerant genotypes can already be used to establish commercial coast redwood plantation for future German forestry.