Several poplar species within a section, but also between sections, are cross-compatible, thus a high number of interspecies-hybrids occur naturally or have been artificially produced during the last 100 years. Very often, systematically kept records on the production or vegetative propagation of poplar hybrids and/or clones have not been available to date. Hence the origin of the poplar plant material used for the generation of hybrids or clones is not quite clear in many cases, thus making the differentiation between the clones a difficult task. Therefore, genetic markers are needed to clearly identify and differentiate the species and hybrids in the genus Populus, including both identification of existing clones and the breeding of new ones. One aspect of this study is therefore to develop molecular markers for the identification and differentiation of species, hybrids, and clones of the genus Populus.
Different species of the genus Eucalyptus, originally native to Australia, are being cultivated in different parts of the world due to their fast growth and beneficial wood properties. In Mexico, probably up to 25 different Eucalyptus species (many of them with unknown species declaration) were introduced early in the 20th century. Many Eucalyptus species are cross compatible and information about provenances of the single eucalypt species is rare. In this study, an experimental plantation established in 1984 and located in Northeast of Mexico was chosen as example to re-assign the species name of six randomly selected Eucalyptus trees growing in this plantation. First, a phylogenetic tree was constructed from complete chloroplast sequences of 31 Eucalyptus species available in the NCBI database. The phylogenetic tree includes three of the nine Eucalyptus species known to be introduced to Mexico, namely E. camaldulensis, E. saligna and E. grandis, which belong to a clade named “Symphyomyrts”. By employing combined BLASTN and UPGMA analyses of six chloroplast (cp) regions, three of the six unknown eucalypt samples (Euc4, 5, 6) cluster together with E. microtheca and E. cladocalyx, whereas the other three (Euc1, 2, 3) were more similar to a group containing E. camaldulensis, E. grandis and E. saligna. UPGMA analysis of the ITS region overall shows the same rough clustering, but provide more detailed information for two samples being most likely assigned to E. camaldulensis.
We have constructed an aspen (Populus tremuloides Michx., line Turesson141) BAC library containing 55,296 clones in total. A random sampling of 86 BAC clones indicated an average insert size of 76 kb with a range of 20 to 160 kb. Twelve percent of the BAC clones in the library have an insert size larger than 100 kb. Based on an estimated genome size for Populus of 500 Mbp, library coverage is about 8 haploid genome equivalents. This library will be screened using AFLP marker identified before co-segregating with gender in a P. tremula x P. tremuloides progeny, where Turesson141 was the male parent.
We describe the development of a SCAR-marker linked to low extractives content of Norway Spruce (Picea abies L [Karst.]) derived from AFLPs. In these analyses 57 different primer enzyme combinations were used in a bulked segregant analysis approach comparing individuals with high and low extractives content. A total of 14 polymorphic AFLP markers were detected between the pools. Five markers were selected for further analyses to verify their linkage to extractives content based on individuals used for pool constitution. One AFLP marker, found to be significant linked to low extractives content was converted into a SCAR marker for further validation. For this marker, a monomorphic band was obtained by using sets of nested primers or restriction site specific primers (RSS) which include the AFLP-restriction recognition site. The separation of the marker from unlinked size homologous marker-alleles was realized by a SSCP-approach. Validation of the marker on different full-sib families confirmed the usability to separate the classes for low and high extractives content of Picea abies.
First results of new trembling aspen (Populus tremula L.) special factorial crosses are presented. At first, productive parent trees were selected: five maternal and five paternal trees without symptoms of heart rot and one tree with fruiting bodies of this fungal attack. The results of phenotypic and genotypic analyses of parent trees, their compatibility, and growth performance are presented. The analysis of the hybrid seedlings’ survival and their growth performance on open ground are shown. Estimates of general and specific combining abilities of the parent trees were carried out and potentially best hybrid families and seedlings were selected.
A preliminary consensus map of Populus tremula x tremuloides has been constructed from an interspecific hybrid population of 66 seedlings of the cross Brauna 11 (P. tremula) x Turresson 141 (P. tremuloides). The map was constructed based on 205 AFLP- and 29 SSR-markers covering 1875cM on 19 linkage groups. A single locus correlating to sex in Populus was mapped close to two AFLP-markers. The map will be used as a starting point for the identification of sex-related genes or molecular markers and their fine mapping based on a BAC-library screening.
The identification of AFLP markers and their subsequent conversion to SCAR-markers linked to wood density of Norway Spruce (Picea abies L [Karst.]) is described for the first time. In AFLP-analyses, 102 different primer enzyme combinations were screened in a bulked segregant approach comparing individuals with high and low wood density. A total of 107 polymorphic AFLP fragments were obtained between the DNA-pools. Twenty-three markers were selected for further analyses to verify their linkage to wood density based on individuals used for pool constitution and additional unrelated clonal material. For 15 markers, a significant linkage to wood density was confirmed by a two-sided Fisher’s-exact test. Four markers were converted into SCAR markers and validated for plant material assayed for wood density by X-ray microdensitometry. For each marker a monomorphic band was obtained using sets of nested primers or restriction site-specific primers (RSS), which include the AFLP-restriction recognition sites. For two markers that are linked to high wood density, a separation from unlinked size homologous marker-alleles was realized by a PCR-restriction approach. Validation of these markers in different full-sib families confirmed their usability to separate the classes for low and high wood density of Picea abies.