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Plant geneticist
Chad Finn evaluates black raspberry plants. Click the image for more
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ARS Scientists Seek Solution for Black Raspberry
Decline
By Laura
McGinnis January 14, 2008
For decades, 'Munger' has been the black raspberry cultivar of choice
for the Pacific Northwest, where most of the nation's black raspberries are
grown. In the 1990s, however, the plants started losing vigor, forcing growers
to seek hardier alternatives. So scientists with the Agricultural Research
Service (ARS) have been working to
identify the problem's origin and develop control strategies.
ARS plant pathologist
Bob
Martin has discovered several viruses that may contribute to the berries'
poor health. The most significant is black raspberry necrosis virus (BRNV),
which has been present in all observed cases with disease symptoms. The severe
form of decline is always accompanied by another virus—raspberry bushy
dwarf virus, raspberry mottle virus (RMoV), or black raspberry latent
virus—or some combination of the three.
Martin, based at the
Horticultural
Crops Research Unit in Corvallis, Ore., and his colleagues have identified
the raspberry aphid as a major culprit in the spread of BRNV and RMoV. Knowing
how aphids transmit the diseases is essential for developing control
strategies.
One potential solution could be to surround black raspberry fields
with "trap plants" that also appeal to raspberry aphids, but are not
susceptible to this severe decline. Instead of spraying the entire field,
growers could simply treat the brdering plants with a low-toxicity pesticide.
Another solution could involve breeding disease- and insect-resistant
black raspberry plants. Corvallis plant geneticist
Chad
Finn and his colleagues collected and assessed 16 different commercial
cultivars from commercial nurseries and the
ARS
National Clonal Germplasm Repository.
The team then crossed the most promising plants and examined their
offspring. Analysis of the initial crosses revealed a dearth of diversity, with
one notable exception. A pair of wild plants from North Carolina consistently
produced vigorous, healthy offspring that seemed to be less susceptible to
disease than the other plants in the study.
The results suggest that it is possible to breed black raspberries for
improved characteristics, but the process could be slow and would likely
benefit from the introduction of wild germplasm.
Read
more about this research in the January 2008 issue of Agricultural
Research magazine.
ARS is the U.S. Department of
Agriculture's chief in-house scientific research agency.
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