Harnessing genetic variation in Swedish forest breeding programs for increased forest health
A long-term goal for my research is to increase the knowledge about the genetic components controlling disease resistance in forest trees and to develop a tool-kit that tree breeders can use to select trees with better disease resistance. Examples of ongoing projects are:
Heterobasidion resistance in Norway spruce – the basis for a resistance breeding programme.
Norway spruce (Picea abies) is an important conifer species both ecologically and economically. Its timber is used in building and for pulping. The major pathogen on Norway spruce in Europe is the root-rot fungus Heterobasidion spp. these fungi usually cause stem rot and reduced growth, the economical losses due to stem rot are significant.
Through large scale genotyping and phenotyping in the Swedish spruce breeding population it is established that there is sufficient genetic variation in resistance against Heterobasidion in the Norway spruce breeding population for progress to be made. There is no trade-off between resistance and other desired traits in either the material. So, resistance to Heterobasidion could be included in the Norway spruce breeding program without compromising, or with relatively small compromises, on other achievements in breeding. However, we currently do not have methods to perform early selection of resistance.
We are interested in finding out if genomic selection could be used for early selection. Genomic selection builds on statistical models are built from phenotypic and genotypic data. These models are then used to predict which plants that are likely to have better resistance. Together with collaborators at SLU, Skogforsk and SweTreeTechnologies (STT) we aim to develop genomic selection models for Heterobasidion-resistance. In this project we work with the material at the breeding front in southern and middle Sweden. Young plants are phenotyped using the standardized phenotyping methods for Heterobasidion sp. developed by the Forest Pathology group and Skogforsk. The material will also be genotyped using the SNP markers to allow for building and testing genomic selection models. Funding for this work has been obtained from Formas, SSF and STT and its owners.
Breeding for Boundaries -Specificity and generality of quantitative disease responses against necrotrophic stem decay pathogens
This is a basic science, curiosity driven, research project focussing on generating new knowledge on quantitative disease resistance. Quantitative disease resistance (QDR) represents the predominant form of resistance in both natural populations and crops, and resistance to necrotrophic stem decay pathogens is no exception. Yet our understanding of the underlying genetics and cellular responses is relatively limited, especially in forest pathology. The current paradigm suggests that QDR to necrotrophic stem decay pathogens also confer broad spectrum resistance. A paradigm can probably be attributed to the difficulty in determining the exact genotype of the challenging pathogen in field studies, giving a false impression of redundancy in the system. However, we have shown that QDR traits to the two closely related pathogens (H. annosum s.s. and H. parviporum) involve largely different genetic components in Norway spruce.
In the FORMAS financed project “Breeding for Boundaries” we will study QDR in the Heterobasidion/spruce pathosystem focusing on species-specific- and potentially broad-spectrum genetic components. To do this we will use distinct host and pathogen genotypes in combination with detailed genetic, cellular- and histological analyses to provide evidence on and mechanistic understanding of genetic variation that define broad-spectrum components of the QDR but also, and more importantly, mechanisms that are divergent between the two interactions. This is a collaboration with researchers at UPSC, FABI and Skogforsk
New strategies to identify less disease susceptible genotypes in the breeding programs
For many of the economically important forest diseases in Sweden no artificial infection system exists therefore we must rely on the naturally occurring infections to study and identify any genetic interactions that underlie an increased vulnerability to fungal pathogens also in the Swedish tree breeding programs this makes it difficult to systematically test disease resistance in the breeding population.
However, with the available genome data and associated genotyping resources for many important forest trees the so-called Breeding-without-breeding (BWB) strategy is an interesting way forward. BWB means that the researcher/breeder phenotype and genotype progenies of a defined seed source on already existing forest plantation sites and use the genotype determine the parent- offspring relationship. I wish to use this strategy to understand the genetic components of susceptibility to e.g. Cronartium pini, M. pinitorqua and Diplodia sapinea in Swedish tree breeding programs. Combinations of DNA-based methods (SNP genotyping and microbial metacommunity analysis) can also be used to detect interactions between trees and latent or endophytic pathogens in a similar way. This work is financed by Brattåsstiftelsen, Carl Tryggers Stiftelse and SLU