Linghua Zhou (right) and her supervisor Rosario García Gil (left) after Linghua Zhou's PhD defence (Photo: Sonali Ranade)
Norway spruce is one of the industrially most important trees, also here in Sweden. Its generation time is with about 20 years relatively long making traditional breeding tedious. Linghua Zhou, PhD student in Rosario García Gil’s group, investigated the potential of different genomic-based breeding methods to assist in Norway spruce breeding. She showed that several of these new breeding methods have the potential to improve and speed up the breeding process of Norway spruce in future. Linghua Zhou successfully defended her PhD thesis at SLU on Friday last week, 28th of August.
Tree breeders look for individuals with the most favourable characteristics and use these then as parents in the next breeding cycle. Tree height, stem diameter, wood quality parameters and also resistance to fungi infection are traits the breeders are interested in. Genomic-based breeding methods try to relate such traits to the genetic information of the tree and use then the genetic information to select the best tree candidates for the breeding. Often this can speed up the breeding cycle because the genetic information can be analysed already in young trees when differences in a certain trait might not be seen yet on the tree.
“Genomic selection as one of genomic-based breeding method is applied almost routinely in animal and crop breeding, like for example for cattle, maize or wheat and also the breeding cycle of fast-growing trees like eucalypts and poplar could be shortened using these methods”, explains Linghua Zhou. “Another advantage is that the most interesting trees can be selected more accurately than with just traditional methods.”
Linghua Zhou and her colleagues firstly tried to identify marker regions in the DNA sequence that are determining how a certain trait is expressed in the tree. They focussed on different wood quality traits, like for example wood density and stiffness, but also looked for marker regions that determine the resistance to fungi. Their results showed that the genomic information of a tree partly determines which fungi species colonise the tree’s buds causing potentially a huge financial lost due to fungal infection.
“By genome-wide association study, another genomic-based breeding method, we successfully identified some genes associating with some traits we were interested in. However, they cannot describe the major variance that we see for the trait which means we cannot use them for breeding directly,” says Linghua Zhou. “That is why we moved from genome-wide association studies to genomic selection which uses the full genomic information instead of just certain DNA regions to predict the trait values of our population of trees.”
The main challenge Linghua Zhou and her colleagues faced during their analyses was the still low quality of the sequenced Norway spruce genome which limits the power of the genomic-based breeding methods. Also, the number of tree individuals that were analysed was partly too small to really use some of the methods to their full extent.
“Our results help to improve the understanding of genetic structure for some complex traits for Norway spruce. And even though genomic-based breeding has limited power at this state, I believe that it will be the trend in future for Norway spruce breeding,” concludes Linghua Zhou.
About the public defence:
The public defence took place on Friday, 28th of September at SLU Umeå. Faculty opponent was Marcio Resende from the Horticultural Sciences Department of the University of Florida, USA. Linghua Zhou's supervisor was María Rosario García Gil. The dissertation was live broadcasted on https://play.slu.se/.
Title of the thesis: Towards genomic-based breeding in Norway spruce
Link to the thesis: https://pub.epsilon.slu.se/17349/
For more information, please contact:
Linghua Zhou
Department of Forest Genetics and Plant Physiology
Umeå Plant Science Centre
Swedish University of Agricultural Sciences
Email: