7-Business: Transgenic cotton has ways to go in quality
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-------------------------------- GENET-news -------------------------------
TITLE: Transgenics have ways to go in quality
SOURCE: Delta Farm Press, USA, by Forrest Laws
DATE: 22 Aug 2005
------------------- archive: http://www.genet-info.org/ -------------------
Transgenics have ways to go in quality
Quick! How many cotton varieties can you name that were among the most
frequently planted in 1995? Here's a clue -- most of them only had two or
three numbers, and they didn't have the letters B or R in their names.
Cotton growers have seen a lot of changes in varieties in the last 10
years, but the changes have not always been for the better when it comes
to fiber quality, according to a plant breeder with the University of
Since 1995, Arkansas producers have switched from 100 percent
conventional varieties to less than 1 percent conventional or
nontransgenic varieties in 2005, said Fred Bourland, director of the
Northeast Research and Extension Center in Keiser, Ark. But fiber
characteristics have not shown much improvement.
"The transgenic varieties, for the most part, have gone the wrong
direction on quality," said Bourland, who participated in a panel on
Georgia's cotton fiber quality at the 2005 Engineered Fiber Selection
(EFS) Conference in Memphis, Tenn.
An update on the Georgia situation was included in this year's conference
after mill buyers said they were having problems spinning cotton from
that state in a presentation at last year's EFS meeting. Similar
complaints were lodged at this year's conference, but Georgia Extension
specialists said growers are still finding markets for their cotton.
Transgenic varieties have produced higher lint yields -- a 12-pound
advantage -- in the 1996-2004 University of Arkansas Cotton Variety Tests,
Bourland noted. (Although test data from Arkansas was used in the
presentation, the trends are similar for most U.S. cotton production
regions, he says.)
"In four of the first six years, conventional entries yielded more than
transgenic entries," he said. "However, lint yields of transgenic entries
relative to conventional entries have steadily increased over the past
"This trend suggests that transgenic varieties have not imposed a drag on
lint yield in these tests and that relative yields of transgenic entries
are improving. An alternative interpretation is that the relative yields
of conventional varieties have not improved."
Among the transgenic variety types, the Liberty Link and BXN transgenics
appear to have the most positive effect on yield, he said, although with
only one year of testing, the conclusion may be premature for Liberty
Link. "BXN entries consistently provided improved yields over
conventional entries, but BXN cotton is no longer on the market."
Over all the years, Bt and BR (stacked gene) entries had higher lint
yields than conventional varieties. "In these tests, any entry possessing
the Bt gene (either alone or stacked with Roundup Ready) has the
advantage of Bt toxin control of sub-threshold injury associated with
certain insect pests," said Bourland.
Roundup Ready varieties (without the stacked gene) have yielded less than
the conventional entries. "The first Roundup Ready varieties yielded very
well compared to conventional, but most of those were removed from the
market due to their susceptibility to bronze wilt," he notes.
"Since 1996, Roundup Ready entries have consistently yielded less than
conventional entries until this trend was reversed in 2004. Additional
testing of new Roundup Ready entries is needed to determine if this
reversal reflects actual improvement in Roundup Ready entries."
Among the fiber properties, Bourland says, the largest variations are
occurring between strength, micronaire and length.
"Although the differences were not great, transgenic means for each of
the fiber parameters (except elongation) were in the wrong direction with
respect to improved fiber quality. Overall, fiber of conventional
varieties was finer (lower micronaire), longer, more uniform and stronger
than fiber of transgenic varieties."
He said the trend of increasing micronaire in transgenic varieties
appeared to be reversed in 2001 through 2003, but was present again in
2004. Other than in 1996, strength of transgenic entries was less than
strength of the conventional entries in all 10 years. "This suggests that
improvement of fiber quality has not been a major goal in the development
of transgenic varieties."
Bourland acknowledges that means or averages of entries in variety tests
do not always reflect performance of varieties planted by producers. From
1995 through 2004, seed companies entered an average of 36 varieties in
the Arkansas Cotton Variety Tests. But the three most planted varieties
in each of those years occupied two-thirds of the cotton acreage in north
Variety performance may also be affected by a certain degree of
inbreeding, he notes.
"The top varieties in the tests represent a relatively narrow genetic
base, particularly considering that (1) Deltapine 20, Deltapine 50 and
Deltapine 51 were derived from the same parents; (2) Stoneville 474 is
the recurrent parent for BXN47, ST4793RR and ST4892BR; and (3) Stoneville
132 was directly derived from one of two parents of the conventional line
used to develop Paymaster 1218BR."
The yield, micronaire, length and strength of the top three planted
varieties in the Arkansas Cotton Variety Tests were consistent over the
"The principal varieties used by producers tended to have higher yields,
but coarser, shorter and weaker fibers than the average variety in the
tests," said Bourland. "These trends suggest that producers tend to
choose varieties on yielding ability rather than fiber quality.
"Although these data represent only the north Arkansas region, the
dominance of a few varieties, the narrow genetic base of the few
varieties and the priority on yield over fiber quality when choosing a
variety appear to be common trends in most U.S. cotton growing regions."
Trying to breed new varieties for higher yields, strength, length, length
uniformity, premium micronaire and other quality factors is not an easy
task, Bourland concedes.
"The late Dr. Bob Bridge liked to compare cotton breeding to trying to
get a bunch of monkeys up a tree," he said. "About the time you think
they are there, one of them always falls out."
In 2003, nine of the 33 entries in the Arkansas Cotton Variety Test
expressed average or better micronaire, length and strength values than
the test mean. Those included ST5599BR, five FiberMax varieties, an
Arkansas breeding line and two Deltapine varieties. Only four of those
produced yields that exceeded the test mean.
"As indicated by a few notable examples, high yields and excellent fiber
quality can be combined in the same variety," says Bourland. "The
scarcity of notable examples is indicative of how difficult it is to find
this combination. With changes that have been and are occurring in
marketing of cotton, it is essential that breeders successfully improve
both lint yield and fiber quality."
European NGO Network on Genetic Engineering
Hartmut MEYER (Mr)
In den Steinäckern 13
D - 38116 Braunschweig
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