A fast and simple genetic survey reveals the spread of poplar hybrids at a natural Elbe river site

Abstract

It is known that various poplar species and cultivated poplar hybrids have the potential to interbreed and produce fertile offspring. Conservation strategies for the genetic resources of the endangered Eurasian black poplar (Populus nigra L.) thus rely on a monitoring which enables the identification and verification of the pure species status. At the same time, the risk of hybrid dispersal and introgressive gene flow has to be estimated. In the present study a combination of two molecular markers, one from chloroplast DNA and the other from nuclear DNA, was applied to evaluate a large P. nigra population on the Elbe River. Hybrid clones of P. · canadensis are scattered within this population and also occur as plantations in the surrounding landscape. By means of the DNA markers the taxonomic status of 208 adult trees in the population and 140 young poplars along the riverbank was monitored. From the analysed young poplars, almost 20 percent were found to exhibit at least one of the two P. deltoides or P. · canadensis diagnostic alleles or genotypes, respectively. Possible vegetative spreads of F1 hybrids and precedent mating scenarios are discussed. Most interestingly we found clear evidence for a small number of backcross hybrids where P. · canadensis acted as pollen donor. This case had long been debated and thought to be less probable, so far.

Scientific Basis for Sustainable Management of Eucalyptus and Populus as Short-Rotation Woody Crops in the U.S.

“…from plantations should be possible to manage with appropriate monitoring, but this should be evaluated further before Eucalyptus spp. are adopted for widespread planting.‖ Unlike Eucalyptus, invasiveness of Populus has not been widely discussed and most attention has been focused on indirect implications of potential hybridization between exotic and native Populus species [53][54][55][56][57][58]. The dilution or alteration of native populations, potential pest and pathogen outbreaks, and impacts on sensitive ecosystems have been cited as potential risks.…”

Phylogenetic relationships in Betula (Betulaceae) based on AFLP markers

“…Therefore, it is expected that the AFLP marker variation in our data set is a suitable indicator of Betula relationships. Arens et al (1998), Cervera et al (2005), Ziegenhagen et al (2008), and Smulders et al (2008) demonstrated in poplar that the AFLP pattern of hybrid offspring contains bands of both parental species. Therefore, the comparison of AFLP patterns of taxa may serve to identify hybrids.…”

With a little help from my friends: hybrid fertility of exotic Populus x canadensis enhanced by related native Populus nigra

“…In contrast, along other European rivers e.g. the Meuse River in Belgium and The Netherlands (Vanden ) the rivers Waal and Rhine in the Netherlands (Arens et al 1998;Smulders et al 2008) and the Elbe River in Germany (Ziegenhagen et al 2008), exotic genes of P. deltoides were detected in young poplar seedlings colonizing the river banks. Progeny testing of seeds harvested on P. nigra revealed that natural backcross events of P. nigra with pollen of P. x canadensis are rare and seem to occur only occasionally in solitary females when male hybrids are locally abundant (Heinze 2008;Vanden Broeck et al 2004).…”

“…Most of the work has been descriptive, documenting the presence of P. deltoidesspecific alleles in wild populations of P. nigra that grow near cultivated clones of P. x canadensis. Some of these studies provided evidence based on diagnostic molecular markers that clones of P. x canadensis and P. nigra do interbreed in both directions (Heinze 2008;Vanden Broeck et al 2004;Vanden Broeck et al 2005, Ziegenhagen et al 2008. Although hybrids are present almost everywhere in Europe, hybridization seems to depend heavily on local conditions.…”

“…Progeny testing of seeds harvested on P. nigra revealed that natural backcross events of P. nigra with pollen of P. x canadensis are rare and seem to occur only occasionally in solitary females when male hybrids are locally abundant (Heinze 2008;Vanden Broeck et al 2004). It is therefore hypothesized that the introgressed seedlings found along European river banks originate from intraspecific crosses of P. x canadensis trees or from open pollinated P. x canadensis females with P. nigra as the pollen donor (Benetka et al 2002;Heinze 2008;Ziegenhagen et al 2008). This pattern of asymmetric hybridization is somewhat contradictory to the fact that F1-hybrids of Populus sp.…”