Context

Due to new pests, pathogens (including fungi, bacteria, viruses which can cause disease), and climate change, we need to breed stronger broadleaved trees more quickly. New DNA sequencing technologies have enabled a better understanding of tree genetics, making it possible to speed up breeding using genetic markers.

However, trees can take many years to flower for the first time (their ‘juvenile’ stage), meaning that breeding is still a slow process. One way to get around this is to make trees flower earlier, using a technique called ‘speed breeding’ which has already been successful in annual crops such as cereals, and does not change the trees genetically.

Scientists at Niab have been able to make apple trees flower years earlier by growing them under conditions with longer daylight hours, high carbon dioxide, and short artificial winters. This project will now test whether the same method can work for silver birch, oak, and ash, with a focus on the latter due to the threats faced both from ash dieback (Hymenoscyphus fraxineus) and emerald ash borer (Agrilus planipennis).

Research aims and objectives

Aim:

Trigger early flowering in ash via environmental manipulation: using long day lengths, high carbon dioxide, and artificially short winters.

Objectives:

• Experiment on ash saplings, a proportion of which will be descended from parents resistant to ash dieback, which may be a resource for future breeding programmes.
• Test silver birch under the same conditions – silver birch has previously been shown to flower early under speed breeding treatments, so will be the control in the experiment.
• Test a small number of oak saplings under the same conditions – oak usually takes much longer to start flowering (25-40 years), and so speed breading treatments may not be successful.
• Compare how genes behave differently in trees grown with speed breeding methods compared to control conditions in all three species. By doing this over time, a better understanding of the genetic changes that help trees to flower faster will be gained.
• Test a diverse population of ash trees from across the country will be collected to see if there are genetic differences that make ash more or less responsive to speed breeding.

Expected outcomes

• Establish that speed breeding can be achieved in ash and oak trees.
• Create a reliable method to make UK broadleaved tree species flower earlier.
• Map the genetic changes that happen in birch, ash, and oak under speed breeding conditions, to see if they share the same response. This will help to enable future prediction of whether speed breeding will work in other tree species and improve the method in future.
• Identify whether certain ash trees are more responsive to speed breeding conditions than others and identify which genes may be responsible.