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Fusarium fighters making headway

Some crops are closer than others, but fusarium resistant varieties are inching closer to commercialization.


November 16, 2007
By Bruce Barker

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32aThe good news in the battle against fusarium head blight (FHB) is that 2004
went down as a low-impact year. The bad news is that as a result, assessment
of fusarium resistance in experimental varieties suffered.

"In 2004, the nursery was not successful in helping assess fusarium resistance.
The late planting and cold weather resulted in low fusarium pressure,"
explains Jeannie Gilbert, a plant pathologist at Agriculture and Agri-Food's
(AAFC) Cereal Research Centre at Winnipeg. "We didn't see anything new
in the nursery, as far as assessments go."

The fusarium nursery at Glenlea, Manitoba, was established in 1994 after the
worst FHB epidemic on record to hit the province. Funded by AAFC, the nursery
is used as a tool to annually evaluate the co-operative trial wheat entries
for western Canadian breeders, which provides information for the registration
process. Currently between 8000 and 10,000 entries are evaluated at the nursery.

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"Some lines are showing very good resistance but there are a lot of other
traits besides fusarium resistance that need to be considered," says Gilbert.
"There isn't a magic bullet for breeding fusarium resistance into wheat."

Plant breeders, though, are making headway. A recently recommended Proven Seed
variety, BW297, is working its way through seed multiplication with the first
commercially available certified seed likely in 2006. Proven Seed will market
it as 5602HR. It is rated as moderately resistant, and is an important step
in the fight against fusarium.

Proven Seed joint ventures their wheat breeding program with an American company
called AgriPro Wheat, the largest supplier of wheat seed in North America. Wheat
breeder Kevin McCallum says that 5602HR fits somewhere between AC Barrie, which
has an intermediate or fair resistance, and Alsen, a well-known US variety,
which is rated as moderately resistant to resistant. Alsen was not registered
in Canada because of quality concerns.

5602HR performed well in co-op registration trials. In the 30 locations from
Regina to Winnipeg, it out-yielded AC Barrie by about nine percent. 5602HR also
had an average one percent higher protein content than AC Barrie.

Looking past 5602HR, Gilbert says the difficulty in getting even better resistance
is finding and transferring suitable genetic material into our wheat lines.
The basis of most fusarium resistance has been the Chinese strain Sumai-3. It
has been used in Canadian breeding programs, as well as many others around the
world. "In Europe, they are moving away from Sumai-3 and are looking for
potential resistance from other lines. We know there are other lines in Asia,
Japan and Brazil with resistance, as well," explains Gilbert.

The ideal scenario would be to build a variety with crosses from three different
sources of resistance. "That would help to confuse the pathogen, reduce
the selection pressure and make it more difficult for the pathogen to overcome
resistance," explains Gilbert.

Barley lines moving along
In barley breeding programs, plant breeder Bill Legge at AAFC Brandon says breeders
only started to make crosses for fusarium resistance in the mid-1990s. "We've
been able to identify the levels of resistance in existing and advanced lines
to help bring some resistance into the program. Resistance, though, tends to
be inherited with poor quality traits, so it takes time to get everything together
in one line."

Legge says that several lines with better fusarium resistance were put forth
in the 2004 co-op registration trials; two potential malting lines and one feed
line. He says only time will tell whether they show enough promise to be registered.
Plus, the malting lines need to go through several more years of malting and
brewing quality evaluation to ensure acceptance in the marketplace, even if
they make it through the co-op testing system. "In the nursery, these lines
have shown 40 to 50 percent lower DON content than AC Metcalfe. In barley, visual
symptoms aren't closely related to DON content, so we need to analyze DON content
as well," says Legge. "We are making good progress, though."

Legge says the likely progression for building fusarium resistance into barley
will start with two-row lines since six-row varieties have twice as much DON
content, on average. Two-row hulless varieties are showing the greatest potential,
partially because they have less DON build-up. Two-row feed barley will likely
follow, and two-row malt will be the hardest to develop. Most of the emphasis
in the US is on six-row malting barley since that is the major market for six-row
malt.

What to do in the meantime?
When it comes to minimizing the effect of fusarium on the farm, bear in mind
that some crops are more susceptible than others. Durum wheat is the most susceptible,
followed by soft white spring wheat, CPS wheat, winter wheat, Canadian Western
Extra Strong wheat, hard red spring wheat, triticale, six-row barley, two-row
barley and finally oats as the least susceptible. However, under conditions
favourable for disease, all small grain cereals will sustain damage.

In areas like the Red River valley where fusarium is common, selection of a
suitable crop and variety should definitely consider fusarium resistance as
part of the selection criteria. However, current registered varieties, and even
a moderately resistant wheat variety like 5602HR, may suffer some damage from
fusarium. In these areas, the strategy must revolve around minimizing the effects
of fusarium and the build-up of DON. Fungicide application may be part of minimizing
the disease effects, particularly in wheat.

Paul Laflamme, provincial integrated pest management specialist with Alberta
Agriculture, Food and Rural Development, says that in areas with very low levels
of fusarium, such as western Saskatchewan and Alberta, selecting a variety with
any level of resistance may help slow the development of fusarium. Still, when
the choice is between a high yielding spring wheat like Superb (rated poor),
and others with a fair rating, it is a difficult choice since Superb yields
so much higher than other varieties.

"Under low pressure, there is some validity in selecting varieties with
better ratings, and it might help to slow the development of the disease in
Alberta," says Laflamme.

Eventually, the goal is to have varieties that are resistant, although not
completely immune to fusarium. In Alberta and western Saskatchewan, the hope
is that these new varieties will come along before an epidemic year strikes.
In areas with fusarium already well established, resistant varieties might make
cereal production more viable.

"I don't think we will ever see anything that is completely immune to
fusarium, nor would we want to. If that happened, the fusarium would probably
mutate and overcome the resistance. We are going to have to learn how to live
with some low level of fusarium, but hopefully the resistance will help to prevent
the build-up of DON to economically damaging levels," says Gilbert. -30-