Research in Ann-Christin Rönnberg Wästljungs group

Genetic background of complex traits in Salix

The overall goal of our research is to understand the genetic basis of phenotypic variation in traits affecting biomass production in Salix, such as drought and heat tolerance, resistance to leef beetles (Chrisomelidae), gall midges (Dasineura spp.) and to leaf rust (Melampsora spp.), as well as phenology traits (bud burst and growth cessation). This research is part of a joint project called “SAMBA" (SAlix Molecular Breeding Activities). We have developed genetic linkage maps, which we use in QTL analyses and we have together with researchers at Rothamsted Research developed an association mapping population for studies of the genetic background of the different traits. We have also sequenced the whole genome of an individual of S. viminalis as well as transcriptomes and are working with the assembly of the sequence data. The genome and the transcriptome information will be of great importance in our search for important genes in different traits.

Our aim is to find markers in candidate genes in the Salix genome strongly associated with the phenotypic variation. These markers will be used as a selection tool for early screening in the breeding of Salix. Our species of interest are the most commonly used in commercial breeding of Salix; S. viminalis, S. dacyclados, and S. schwerinii.

Salix (willows) belong together with Populus (poplars, aspens) to the Salicaceae family. According to interpretation of available fossil data, both Salix and Populus occur in middle Eocene sediments that are around 45 million years old suggesting the lineages diverged around that time. The two lineages share a whole-genome duplication that took place much earlier than their divergence. The two lineages have similar karyotypes (n=19) and collinear genetic maps support the conclusion that Salix and Populus share the same large-scale genomic history. The black cottonwood (Populus trichocarpa) genome has been sequenced and the genomic information from Populus can be applied on Salix because of the shared genomic properties.

Salix includes about 400 species mainly distributed in temperate regions and 24 of these species are found in Sweden (Den virtuella floran). Salix has a very long cultivation history that dates back to Roman times when it was mostly used as raw material for production of baskets, which were needed for transportation of goods in the extensive trade at that time. Nowadays, Salix is considered one of the most advanced energy crops in temperate regions owing to its potential for high biomass yields in short time frames, an ability to resprout after multiple harvests, simple and low-cost propagation from cuttings and a broad genetic base. Salix also have a very energy efficient production system where the produced biomass yields 20 times more energy compared to the energy input.

Agencies that support the work

Swedish Energy Agency (STEM)

ERA-NET Bioenergy

The Swedish Research Council Formas