Improvement of forest reproductive material for ash: characterizing the resistance against ash dieback (Askskottsjuka)

The overall aim of the work is to support the development of a more resistant population of F. excelsior for planting in Sweden.

European ash is threatened by an alien invasive fungal pathogen intro­duced from Asia. The rapid spread and intensification of the disease has resulted in a serious population decline; since 2010 ash is a Red-listed species in Sweden. Genetic resistance is an important tool for disease management. Large variation in susceptibility to the pathogen has been observed within natural populations; less than 5% of trees show disease resistance.

During 2013-2015 we identified a large number of vital ash trees from areas of high disease pressure across the whole range of the ash distribution area in Sweden, and propagated a first test population. This project builds on those efforts to now implement the research into practice by establishing a field trial using the propagated selections of wild-type genotypes to screen for, and characterize, the resistance. This work is critical to enable targeted genotypes to be selected for further commercial propagation, breeding and future establishment of seed orchards.

In addition, the project will identify biomarkers associated with ash resistance that can be used in marker-assisted selection of new genotypes - a popular approach for precision plant breeding. A state-of-the-art chemical fingerprinting technique known as Fourier-transform infrared (FT-IR) spectroscopy and chemometric modelling will be used on a unique collection of material acquired from genetic field experiments to i) discriminate between resistant and susceptible ash genotypes, and ii) predict the concentration of putative phenolic biomarkers of resistance; which can potentially, significantly expedite current selection and screening protocols for breeding efforts.

This work, aimed at characterizing and developing a more resistant ash population for planting, will be extremely important for the restoration, regeneration and sustainable managment of this important noble broadleaved tree species in Swedish forests, cities and other urban and natural landscapes.