Resiliency in corn often under-estimated
November 13, 2007
By Ralph Pearce
Ability to adapt is just as important as other crops.
For years, growers have been hearing about the resiliency of soybeans. Singular
stresses like a wet spring or mid-season dry spell rarely affect their yield.
Now corn is showing signs of resiliency of its own. Part of this comes from
improvements through breeding, with increased diversity in germplasm through
the development of more hybrids with different genetic backgrounds. The impact
of seed treatments also helps with the plant's tolerance to adversity.
Appearances can be deceiving
In 2005, corn fields outside of St. Marys, Ontario were literally shredded by
an early July hailstorm. Yet within two weeks, almost all of the plants were
showing new leaf growth and little evidence of any significant losses. To Adrian
de Dreu, that comes as no surprise. The physiology of the corn leaf is such
that the veins run parallel to the stalk. "Even if they're torn a bit,
the plant can still translocate sugars through the leaf and continue to survive,"
says de Dreu, the corn breeder for Syngenta Seeds near London, Ontario. "Hail
tends to be a smaller issue compared to other crops."
A bigger issue is advancements in breeding, along with the trend towards earlier
planting. He cites the 2005 case where some were planting April 15th, which
would have been 'unheard of' not that long ago. "Corn's becoming more resilient
over time, and that's why we're seeing increased yields over time," explains
de Dreu. "Part of that is from breeding efforts and improvement in germplasm,
and the other part is management."
The impact of seed treatments cannot be discounted either, he notes. Maxim
Apron is now an industry standard and Cruiser has shown an average six bushel
per acre advantage.
Disease the big factor
As a breeder, de Dreu believes disease resistance and tolerance are keys to
corn's resiliency and improved performance, yet they are often overlooked. "In
standability, stalk rot is a major factor and we've seen some of our major losses
in yield from diseases like rust," explains de Dreu, adding fusarium stalk
rots, crown rots and smut as other diseases to monitor.
Another disease he believes is coming with greater frequency and showing up
earlier each year is anthracnose. "We don't notice it until the plant suddenly
dies, and then it just finishes it off," says de Dreu. "It appears
it just came in at the end, but it's been gradual and we often miss those symptoms."
One of the ways he is trying to improve disease resistance is to incorporate
greater genetic diversity into Syngenta hybrids. But growers could help themselves
by planting hybrids from more than one company, although it can be difficult
in the face of volume discounts and other incentives. "But that's why I've
been trying to add diversity within our brand, so our customers will have diversity
within those hybrids," says de Dreu.
A variety of sources
Resiliency in corn comes from different factors, according to Mervyn Erb. As
an independent crop consultant from Brucefield, Ontario, Erb believes corn's
improved performance can be traced to various stages of its development. "The
hybrids we have today are definitely more cold tolerant," says Erb, citing
research in the early 2000s, comparing new hybrids with those from the 1960s.
"They found a big difference in their ability to come up under cold soil
conditions. There are varieties I know I can plant on the 18th of April, with
extraordinary vigour and growth, no matter what."
The notion that corn seed could sit in the ground for as long as four weeks
before emerging to yield a solid crop would not have been considered 30 years
ago. Erb agrees with de Dreu's assessment of seed treatments. Other influences
are improvements in harvesting and drying of seed, as well as handling and storing.
"Less seed damage, better storing ability, seed treatments, variety selection,
it's all coming together," says Erb.
But it is improved growth in what was considered adverse conditions that is
the biggest advancement. "If you get cold, wet weather and not much sunshine,
some plants just get yellow and go backwards, but other plants can yellow and
still grow," says Erb, noting many fields in 2004 and 2005 which looked
very stressed in the early season still yielded above expectations. "That's
internal, that's varietal, that's early growth tolerance and the ability to
grow in adverse conditions. Even though we had some poor weather earlier in
May, we had all kinds of girth on the stalks and the cob."
Erb stresses that increased resistance or tolerance to disease and environmental
extremes will be necessary given the onset of diseases. He believes plant diseases
will increase in the coming years as a result of increased crop residues.
"We never even considered northern corn leaf blight, grey leaf spot or
anthracnose in the past," says Erb. "We have them now, and the trash
issue is going to make this more apparent, so the challenge is to keep good
plant health while still maintaining yield, roots and stalks, and that's hard
to do all at once." -30-
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