Breeding ash trees for tolerance to ash dieback

Forest Research have been engaged in efforts to improve tolerance of ash trees to ash dieback caused by Hymenoscyphus fraxineus (previously known as ‘Chalara‘) since the disease was first recognised in Great Britain in 2012.

Progress has been made under three main projects:

• Living Ash Project 
• Ash dieback mass screening trials 
• Testing a range of ash species for tolerance to ash dieback

Across these three projects, we have established fourteen mass screening trials, three progeny trials and two ash species trials.

• So far, we have selected nearly 700 trees with good tolerance to ash dieback, replicated these by grafting and secured them in a clonal archive alongside trees selected in situ by the Future Trees Trust. A second campaign of selection will take place in 2022.
• We have tested options for mass propagation of ash trees using tissue culture.
• We have examined whether tolerance of ash trees varies among seed sources.
• We have estimated genetic parameters at an early age to understand how to proceed with tree breeding.
• We are investigating variation in tolerance between different ash species.

In the Living Ash Project phase II, we are currently engaged in:

• Maintaining our experiments so that they can be re-assessed in 2022. These will be searched for the most promising trees for further breeding work.
• Establishing artificial inoculation tests on selected individuals to confirm levels of tolerance under controlled conditions.