Background and Objective

Main objectives are selection, genetic characterisation, testing of resistance, and hybridisation of poplars within the section Populus as well as the cultivation of plants for test plantations. Plus trees and stands of black locust will be selected and tested in short rotation plantations. Basic material for tested reproductive material suitable for short rotation should be approved.

Approach

Working packages

1. Building up of clone collections with plus trees and proved parents
2. Continuation of poplar hybridization with further parent trees to extent number of progenies as basis of breeding progress
3. Assessment and evaluation of resistance of poplars within the section Populus
4. Further development of molecular markers for identification, characterisation and species determination
5. Investigation of resistance against damaging insects
6. breeding of triploid aspen clones with higher growth performance
7. selection of progeny stands and trees of black locust (Robinia pseudoacacia) as basis for new seed orchards
8. evaluation of existing clonal tests of poplars and willows

Results

The main results of the project are:

• Two crossing series were carried out. The progenies were planted in 3 series at 11 sites. About 950 poplar samples from the Thünen Institute and other project partners were analyzed with molecular methods.
• Growth parameters were measured in the progeny trials that have been established since 2010. In the oldest series, 6 hybrid aspen had a significant better biomass production compared with the control, and 9 hybrid aspen in the series of the following year. 4 of these hybrid aspen progenies already produce over 10 t_atro/ha/year. There are also hybrid aspen progenies and clones in the younger trials series, which perform better in growth than the standard.
• Biomass functions were set up for the individual trials. A general, environmental independent biomass formula could not be found.
• The infestation of aspen progenies with Melampsora, Polaccia and bark canker was low in the study period. The selection of less susceptible clones as crossing partners and progenies for the practice can reduce the risk of infestation.
• In the clone tests with poplars, the clone 960 is growing well on all test sites. The clones 962 and Hybride 275 have as well a good growth performance on many sites. Among the new selections from North America, there are five clones that are promising. In the tests with willow, the Swedish clones Tordis and Sven provide good yields.
• The testing of poplars with different ploidy levels showed that 14 triploid clones have significantly increased shoot growth in the field compared to the fast-growing triploid reference clone "Astria".
• Differences in growth performance and stem quality were observed between seed stands and seed orchards of different origin of black locust. The use of selected plus tree clones has proven to improve growth and stem quality.
• Nuclear markers for species identification were developed for 19 poplar species and grouped together in a marker set. Furthermore, species-specific mt-markers were detected for 4 poplar species.
• The comparison between samples damaged by beetles and those, which are undamaged, result in about 33,000 transcripts. Here, 1,802 transcripts were found to be significantly differentially expressed.
• Transcriptome analysis revealed no differences in expressed genes based on the pre-selection of tolerant and sensitive clones. The assessments of leaf loss and insect infestation should take place over a longer period of time (including years with calamities).