By Top Crop Manager
Current research trying to build resistance.
As fusarium head blight (FHB) continues to be a problem across much of North
America, cereal breeders and researchers are trying to develop resistance to
FHB using a variety of means, from molecular markers to wild barley ancestors.
Dr. George Fedak, a researcher with Agriculture and Agri-Food Canada's Eastern
Cereal and Oilseed Research Centre in Ottawa, acknowledges the need to introduce
new genetic material into wheat and barley varieties in an attempt to combat
the effects of FHB. In the past 10 years, the condition, widely regarded as
more of a problem in wheat in Ontario than in barley, has gained considerable
attention for its effect on milling and feed quality in wheat, especially where
deoxynivalenol or DON levels are concerned.
In feed usage, DON is an antimetabolite which causes animals to eat less thereby
reducing weight gain. At higher concentrations, it can cause reproductive and
immune system failure.
In barley, the presence of DON is also a concern. In malting barley, there
is zero tolerance for any levels of DON which can cause 'gushing' in beer. But
again, says Fedak, the need to introduce new genetic material is of particular
concern. As selective breeding has enhanced desirable traits, it has also removed
some of the genetic diversity needed to develop resistance and tolerance. "We're
targetting fusarium because really, in neither wheat nor barley do we have any
source of immunity," he says. "We're going to have to build it up
and hope to get materials from unrelated sources that maybe have equal resistance."
Hunting in the wilds
Fedak has been looking at crosses of cultivated barley and two wild ancestors,
Hordeum spontaneum and Hordeum bulbosum, just two of more than 20 wild relatives
of barley, including the foxtail family of weeds. As part of a project that
was funded by the Oat and Barley Council of Ontario, Fedak has been studying
the potential for developing fusarium resistance in barley, since none exists.
In general terms, two row cultivars with the variety Rodeo in their ancestry
have higher levels of tolerance than six row cultivars. Only Chevron, an older
six row cultivar that has not been adapted to Canadian growing conditions, shows
any superior tolerance.
Using spontaneum-derived material, Fedak has screened several hundred lines
from the greenhouse and growth chambers, which were inoculated, then rated on
the percentage of florets that were infected. The theory behind this work is
to find resistance to various diseases, not just fusarium. "We're finding
that in some cases, where we've got resistance genes, there are clusters of
them," explains Fedak. "If you've got resistance to one pest or disease,
it could be resistant to others."
Early in 2004, Fedak found some six-rowed lines that appeared better than Chevron.
"Our barley breeder, Dr. Keh Ming Ho, is now crossing these new selections
with his best Chevron derivatives, hoping to 'pyramid' the different resistance
genes and produce six-rowed germplasm with enhanced fusarium resistance,"
From the bulbosum-derived material, he adds, they have found some resistance
to rust and are trying to incorporate that into barley cultivars, as well.
But progress is incremental and, as with most research ventures, there is no
one single 'magic bullet' in the making. Like any public program, Fedak concedes
results are attained over a longer period of time, noting there is always a
good deal of interest in such work, but little money to allow for its continued
progress. One development that could help in enhancing the research would be
the use of molecular markers, which may help improve the overall efficiency
in locating resistance genes.