While I recognize and share the concern about the domination
of the soybean industry by RR varieties, it is a little misleading to
claim that the varieties currently being produced are therefore
"monomorphic", in terms of soybean rust. This accusation would only
apply if the rust resistance is "linked" to the RR gene, as was the
case with the Southern corn leaf blight epidemic and the
Texas-Male-Sterile-cytoplasm in the early 1970s. Just as with soybean
now, corn lines were actually quite diverse, except for the particular
TMS trait. Since that trait made corn breeding easier, all corn
breeders used the same trait, and had been for many years. Thus,
although many different varieties of corn were found, they were
monomorphic only for that particular trait. No epidemic occurred
until a new pathogen arrived that could exploit that particular TMS
trait.
It is certainly true that few if any of the varieties
commercially available in the US have resistance to soybean rust, so
in that regard, US soybean is monomorphic. But that may be due in
large part to the fact that US soybean breeders have not been
screening for resistance to the rust, because no one wanted to
introduce the rust to the US in the first place. Furthermore, few
growers will demand disease resistance in a crop for a disease that is
not found in the country. I suspect that there will be a plethora of
rust resistance breeding projects funded next year.
Not all evil in the world comes from Monsanto. The rust
invasions could as easily be blamed on global warming for giving us so
many hurricanes. Or NAFTA for relaxing trade restrictions and
allowing importation of so many exotic pests.
More importantly, the next few years will likely produce a
good test of just how monomorphic soybean is with respect to rust. I
suspect that, among the many varieties currently on the market with
their differences in maturity, nematode resistance, oil
characteristics, and other agronomic traits; some level of resistance,
or at least tolerance, may already be found. And odds are that this
will be more likely among all the varieties that are NOT Roundup
Ready, than among the few lines that are.
Polymorphic or heirloom varieties used by organic growers will
not necessarily have more resistance to rust than any other variety.
In my trials, all heirloom tomato varieties tested were among the most
susceptible to early blight, while hybrids with single gene resistance
perform well. Thus, it would be inappropriate for organic growers to
rely on presumed resistance if that resistance does not actually occur.
Given the slim profit margin on conventional soybeans, use of
expensive fungicides seems unlikely to be widespread, at least until a
season occurs with widespread, demonstrated yield losses. My only
prediction is that a loss of market share for susceptible soybean
varieties seems certain to result.
Jim Kotcon
At 07:39 PM 12/02/2004 -0500, you wrote:
Soybean rust is only new to the USA and Canada where it is called an
asian
soybean rust that blew in from South America on the hurricanes.
The fungicide used to treat it, Headline®, is a member of a
fungicide family called strobilurins. There have been no cancer or
birth
defect studies done on that fungicide as far as I can gather.
The fungus targets cytochrome B respiration.
There is a tangible fear among USDA people, not because the disease is
new so much as because they have gambled on RR soy. Most growers grow
that one
strain - introduced a short time ago in genetic terms.
Essentially the whole crop is monomorphic (having little genetic
variability);
thus a new disease can sweep through and wipe out everything fast.
This is reminiscent of a near total disaster in the US corn crop
in the
early 1970s. Most of the crop was based on a hybrid line with what
was
called the texas (t) cytoplasm. A fungal corn blight appeared that
depended on the
texas cytoplasm and caused about a $10 billion crop loss that led into
a serious economic recession.
The use of RR soy poses a threat because it is monomorphic and the
lessons of that threat are clear!
3 DECEMBER 2004 VOL 306 SCIENCE www.sciencemag.org 1672-3
Plant Pathologists Gear Up for Battle With Dread Fungus
"No soybean can resist a rust that has finally arrived in the United
States, spurring a search for new varieties, predictive models, and
monitoring techniques."
My comments continue as follows. USDA/APHIS knows about the problem of
monomorphic crops and disease but chose to go forward with
corporations
to promote and spread highly monomorphic transgenic crops as is
described below:
" In a 1976 paper entitled "An Evaluation of Special Grant Research on
Southern Corn Leaf Blight," the USDA also acknowledged the genetic
uniformity in the nation's corn crop as one of the primary causes
of the
1970 Corn Leaf Blight. "In the [1960s], it became clear that
relatively
few corn breeding parents were being used to produce the bulk of
American hybrid corn varieties," said the report. "This narrowness of
germplasm set the stage for potential vulnerability to diseases,
insects
and other stresses. In early 1970, environmental conditions in
Southern
and Northcentral corn producing regions were favorable for easy
disease
establishment and spread among vast plantings of highly uniform
varieties. The [Southern Corn Leaf Blight] epidemic became of national
and international significance."
http://www.unsafescience.com/cms-sclb.html
Given weather conditions that enhance spread of the rust fungus the
widespread use of rr soy will require a large and expensive use of of
an apparently virtually untested chemical fungicide.
Organic growers have the inherent benefit of polymorphic varieties and
saved seeds. These are the features that USDA and the corporations
seem
to be trying to wipe out!
********************************************************
To unsubscribe from SANET-MG:
1- Visit http://lists.sare.org/archives/sanet-mg.html to
unsubscribe or;
2- Send a message to <listserv@sare.org> from the address subscribed
to the list. Type "unsubscribe sanet-mg" in the body of the message.
Visit the SANET-MG archives at:
http://lists.sare.org/archives/sanet-mg.html
For more information on grants and other resources available through
the SARE program, please visit http://www.sare.org.
*****
Jim Kotcon
304-293-3911 ext. 2230 (office)
304-293-2872 (fax)
304-594-3322 (home)
West Virginia University
Division of Plant and Soil Science
401 Brooks Hall, P. O. Box 6058
Morgantown, WV 26506
********************************************************
To unsubscribe from SANET-MG:
1- Visit http://lists.sare.org/archives/sanet-mg.html to unsubscribe
or;
2- Send a message to <listserv@sare.org> from the address subscribed
to the list. Type "unsubscribe sanet-mg" in the body of the message.
Visit the SANET-MG archives at:
http://lists.sare.org/archives/sanet-mg.html
For more information on grants and other resources available through
the SARE program, please visit http://www.sare.org.