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What is the context of this research?

The emerald ash borer (EAB) is an alien, invasive

wood-boring beetle that has killed tens of millions of North American ash trees since its accidental introduction from Asia and subsequent detection in 2002. The infestation is still spreading and represents an existential threat to North American and European ash resources, with billions of dollars in commercial and ecological losses.

In contrast, by living along with EAB for millennia, Asian ash species have evolved an unknown set of genes which allow them to resist the beetle’s attacks. Discovering those genes is our goal in this project, with the ultimate objective of breeding North American and European ash trees resistant to EAB.

What is the significance of this project?

Sequenced resistance genes can be used as markers for screening of natural populations, Asian hybrids, and other sources of ash, which would allow for targeted breeding of North American and European ash that can survive attack by EAB. These resistant ash would help replace those initially killed by the borer and offset some of the commercial and ecological losses.

Without genetic markers, each generation of trees in a breeding program would have to be grown for as much as five years until they became large enough to be screened for resistance to EAB larvae. The time savings will be multiplied over each generation in a breeding program. The Ohio Agricultural Research and Development Center has already awarded a $5,000 competitive grant to help support this research.

What are the goals of the project?

To identify the genes that allow certain ash trees to resist attack by EAB, we will compare coevolved (i.e. Asian - resistant) and non-coevolved (i.e. North American - susceptible) ash species. We collected samples immediately before and after attack by the EAB larvae (the life stage that actually kills the tree by feeding under the bark).

We will profile gene expression in resistant and susceptible trees, before and after attack, using a Next Generation Sequencing technique called RNA-Seq, in order to identify genes associated with resistant trees. Using a second approach called quantitative polymerase chain reaction (qPCR), we will more accurately validate the association and identify candidate resistance genes to be used in further investigations.

