Walnut Genetic Secrets Targeted in New Research
Wood September 19, 2008
The rich taste and smooth texture of walnuts make this versatile tree
nut an American favorite. Now, Agricultural
Research Service (ARS) scientists and their
University of California-Davis
colleagues have embarked upon a 4-year study to uncover new clues to this
venerable tree's little-known genetic makeup.
The researchers want to develop what are known as "genetic markers"
that would help tree breeders pinpoint prized walnut seedlings. These
sought-after trees would boast about a half-dozen traits valued highly by those
who grow--and those who eat--walnuts.
The traits range from the plumpness of the kernel to the time of year
the tree comes into leaf, a feature useful for avoiding frost damage and some
The tell-tale markers that ARS geneticist
Aradhya and colleagues are creating are known as "SNPs," short for "single
nucleotide polymorphisms." Ideally, walnut breeders would be able to use these
markers to identify superstars while the trees of interest are still very
young. That's a time-saving advantage when breeding English walnut. This
popular tree takes several years to begin bearing marketable nuts--a long wait
for breeders anxious to determine which candidate trees are the best.
According to Aradhya, the collaboration will also yield several
different kinds of genetic maps. In all, the venture is expected to provide the
most comprehensive picture ever offered of walnut's mostly mysterious genetics.
More than 600 trees are being grown especially for the research, which
is sponsored by the Walnut Marketing
Board, the university, and ARS, a scientific research agency of the
U.S. Department of
The markers will be invaluable for profiling the genetic makeup of the
more than 1,600 walnut trees in the nation's official walnut collection in
Davis, Calif. Aradhya is the geneticist for this collection of wild and
domesticated walnuts, officially known as the ARS
Clonal Germplasm Repository for Tree Fruit and Nut Crops and Grapes.