Genetic mapping of Dutch elm disease resistance

Dutch elm disease (DED) has killed millions of field elms (Ulmus minor) in Britain and Europe since the 1970s, causing incalculable damage to landscapes and their associated biodiversity. While the species U. minor is highly susceptible to DED, some east Asian and Himalayan species of elm are resistant. These Asiatic species differ in their growth and form to U. minor and cannot fully substitute for it in the landscape. Several breeding programmes have attempted to generate trees that combine DED-resistance with the growth and form of U. minor via hybridisation and back-crossing. These have been partly successful, but further breeding is needed to fully realise these ambitions. Most recently in Britain, a complex resistant hybrid Wingham (FL493) was crossed with a surviving U. minor tree in Tonge Mill, Kent. Sixty progeny from this cross were tested for field resistance to DED and show segregation for this trait. Here, we analyse the genome of these progeny in order to: (1) construct a linkage map of the elm genome, and (2) identify regions of their genome derived from east Asian and Himalayan species that could be associated with DED-resistance. Such knowledge could accelerate future breeding programmes and enhance our understanding of the mechanistic basis of resistance.