A new study led by scientists at the University of California, Davis (UC
Davis), and USDA's Agricultural Research Service (ARS) has sequenced the
genomes of the English walnut and its wild North American relative using
long-read DNA sequencing and optical genome mapping. The genome sequences
are the highest quality ever assembled of any woody perennial.
According to Dan Kluepfel, a USDA-ARS scientist and principal investigator
of the walnut-rootstock development project, they chose to cross the widely
used English walnut with the wild Texas black walnut because of its native
resistance to several soil-borne diseases and root nematodes, which are
serious pests of walnut in California.
The scientists produced complete genome sequences of the two walnut species
in the time normally required to produce the sequence of one genome. These
genome sequences will now help researchers identify genetic markers that can
be used to develop new varieties with improved pathogen and pest resistance.