GENET archive


2-Plants: First case of out-crossing of herbicide resistance into Red Rice

                                  PART I
-------------------------------- GENET-news -------------------------------

TITLE:  Clearfield/red rice out-cross confirmed in Arkansas field
SOURCE: Delta Farm Press, USA, by Bob Scott and Nilda Burgos
DATE:   12 Nov 2004

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Clearfield crops are non-GE herbicide-tolerant crops, HM/GENET
thanks to Devlin Kuyek from GRAIN who sent me these articles

Clearfield/red rice out-cross confirmed in Arkansas field

The first Arkansas field with confirmed out-crossing of the trait in CL
161 rice (that conveys tolerance to the imadazolinone family of
chemistry) to a population of red rice has been confirmed in a field in
Jackson County.

The field is included in a survey of Clearfield rice fields conducted by
the University of Arkansas weed science group. The purpose of the project
is to detect out-crossing and determine the frequency at which we can
expect out-crossing of Clearfield rice with red rice to occur under
various conditions.

The study has been conducted with the cooperation of BASF and county
agents of the Cooperative Extension Service. Ford Baldwin and Tomilea
Baldwin of Practical Weed Consultants first examined the field.

They observed red rice plants that looked very much like those that
Tomilea had observed in Clearfield rice plots while she was finishing a
part of her Ph.D. program with the university. Her project then revolved
around Clearfield rice and she happened to observe out-crossing with red
rice in her plots.

After surveying the field in Jackson county, Ford and Tomilea suggested
we might want to look at the field and include it in our program. The
most obvious thing about the field was the presence of large, immature,
compact-growing, erect red rice plants dotted across the field.

We were told that the field received two Newpath herbicide applications
and a salvage application of Beyond herbicide in 2004. Based on
circumstantial evidence, most involved believed we had a case of out-crossing.

BASF sent samples to its lab for analysis. That analysis has now
confirmed that the red rice in question was in fact an F1 hybrid between
some red rice plant and CL 161. We say F1 because this field was first
planted with Clearfield rice last year and there were a few survivors
from last year's Newpath application.

The confirmed hybrids that we saw this season would have been offsprings
of cross-pollinated red rice plants from last year.

The F1 hybrid plants stand out because they are much taller than
Clearfield rice and exhibit a dense and erect vegetative growth habit.
They are also characteristically late in maturity. They are only now
forming seed-heads (see photo) and some of them may not even get to flower.

These distinctive visual traits should help Clearfield rice growers and
consultants watch for the occurrence of herbicide-resistant red rice. The
appearance of F1 plants in the field so far have been consistent with the
F1 hybrids obtained in various gene flow experiments with Clearfield rice
and red rice conducted by the weed science section at the University of
Arkansas and in related experiments conducted by David Gealy at the USDA-
ARS, Stuttgart. The plants are now referred to as bull red rice by some

If the F1 hybrids are allowed to go to seed, the next generation (F2s)
will also have tolerance to Newpath herbicide, but will display a wide
variety of phenotypic or visual characteristics. For instance, the F2
generation will have very early to very late flowering plants. Several
plants will shatter its grains severely like red rice, but some will not.
Plant height will range from about 1.5 feet to 5 feet. Growth habit will vary.

The frequency of occurrence of these characteristics among F2 plants is
currently being documented at the university as part of a graduate
student program. The kaleidoscope of F2 characteristics is not yet fully
understood and can vary according to the red rice parent.

The bottom line is that it will be more difficult to spot all out-
crosses past the first generation. This is one reason that early
detection of out-crossing will be critical to managing fields whenever
out-crossing occurs. Whenever out-crossing is suspected, it is important
that we confirm it, with a combination of herbicide, enzyme sensitivity
and genetic tests, because some red rice biotypes (whether blackhull or
strawhull) also flower late and exhibit an erect growth habit.

Fortunately, due to the late maturity of these F1 hybrids, the seeds were
generally immature at the time the field was harvested. Many of the
surviving red rice plants will not make seed. However, some plants could
still produce viable seed if left until frost.

For red rice, it takes at least two weeks from heading to produce a few
viable seeds. We recommend that the farmer burn the field to singe
existing seed heads or perform some other operations to destroy surviving

In addition, this field provides the first test of the BASF stewardship
program. On this point both BASF and university recommendations agree.
Under no circumstances should this field be put back into Clearfield rice

Crop rotation or leaving the field fallow for at least two years is the
only way to insure that other herbicides can be used to control red rice
that emerges in the field next spring. The most obvious choice for crop
rotation is to Roundup Ready soybeans. This has been part of the
stewardship program from the beginning.

In general, our university recommendation has been to rotate to soybeans
regardless of the level of red rice control obtained or the presence or
absence of out-crossing. In some cases, crop rotation issues are
complicated if the land is leased, lease agreements exist about what
crops will be grown, or the ground may not be practically suited to grow
anything but rice.

However, some action must be taken or it is likely that seed will spread
from field to field with tillage, planting, and harvest equipment. While
cross-pollination has been getting the most press lately, it is probably
the movement of seed from field to field with harvest equipment that
poses the most risk of spreading resistance.

In addition, this case solidifies the stewardship and patent protection
position of BASF of not allowing producers to save seed. After seeing
this field, it is easy to imagine the problems if red rice seed is
harvested and planted in a field the following year. This will especially
be true next year if there are any F2 generations out there.

The basic program for not getting resistant red rice on your farm is
plant certified Clearfield rice seed from approved rice processors, do
not save seed, strive to attain 100 percent red rice control with your
herbicide program, and rotate to a crop like Roundup Ready soybeans the
year following Clearfield Rice. If you do these things, then the
development of Clearfield red rice is pretty unlikely.

The longevity of the Clearfield system depends on our ability to minimize
out-crossing and on how we manage it when it occurs. By utilizing correct
stewardship practices, we should be able to prevent this identified
population from spreading any further.

-Bob Scott is an Extension weed specialist with the University of
Arkansas. Nilda Burgos is a weed scientist with the University of Arkansas.

                                  PART II
-------------------------------- GENET-news -------------------------------

TITLE:  Why Clearfield piracy is dangerous
SOURCE: Delta Farm Press, USA, by David Bennett
DATE:   12 Sep 2004

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Why Clearfield piracy is dangerous

AUSTIN, Ark. -- Having earned a doctorate studying Clearfield rice,
Tomilea Baldwin is an expert on the crop. As of now, she says, the
Clearfield technology "isn't perfect but is undeniably the best way" to
control red rice within a rice crop.

Baldwin works with her weed scientist husband (and Delta Farm Press
contributor), Ford, at Practical Weed Consultants near. She recently
spoke about her experiences with Clearfield and why piracy is especially
threatening to the technology. Among her comments:

On Clearfield rice physiology/environmental interactions:

"Cultivated rice and red rice are of the same genus and species. It's
very possible for out-crossing or hybridizing to occur through transfer
of pollen.

"If pollen is transferred from Clearfield to red rice, the possibility of
the Clearfield gene being transferred is likely because it's a dominant
trait. Meanwhile, the properties of red rice are also dominant. That
could possibly lead to a Newpath-tolerant red rice plant.

"If hybridization occurs, when you spray Newpath, you're selecting for
those hybrid plants. They'll thrive in that environment. Once you begin
selecting with Newpath applications, competition from susceptible plants
is reduced and they'll multiply very quickly."

On how rapidly a hybridization problem can spread:

"In my research plots, beginning in 1998, we were doing efficacy studies
of Newpath on red rice. By 2000, we were noticing that all the red rice
wasn't being killed in the plots. We also noticed red rice and Clearfield
plants were flowering at the same time.

"The following year, we tilled up the plot area as if we were going to
plant a rice crop. We didn't plant one, though -- we just let the
volunteer rice plants come up. We made three Newpath applications: two at
an X rate, and another at a 2X rate.

"What we found was very surprising. We had a segregating population of
Newpath-tolerant red rice. Out-crossing was happening in the previous
years right under our noses and we had no idea."

Are out-crossing concerns overblown?

"Out-crossing concerns aren't bogus at all. I'm seeing this in our
research plots again. Just recently, I ran across a red rice plant in an
alley between plots. The plots and the alley were all sprayed with
Newpath and this plant was very healthy.

"We have efficacy studies that generally include untreated checks, plots
that give incomplete control and others that should give 100 percent
control. And that's what we've found: the various levels of Newpath
applications gave us various levels of control.

"What that created was an environment where red rice and Clearfield rice
were simultaneously flowering. Even though red rice is an earlier-
maturing plant than cultivated rice, it has so many tillers and panicles
it's still flowering when the Clearfield begins. The point is: out-
crossing can happen."

On recommendations, new products and labels:

"BASF suggests two applications of Newpath at 4 ounces. They recommend
that the applications be made when a field has adequate moisture. If the
field is dry, you should flush it.

"But how many growers are going to flush when there's a chance of rain in
two days? If you're chasing a rain, the next thing you know, the product
has been in the field two weeks and hasn't been flushed in. These are
things that concern me.

"There's another BASF herbicide, Beyond, that's coming out. It's very
similar to Newpath with a short residual.

"Beyond is targeted at escaped red rice plants. We've used it in plots
and it works well.

"Currently, though, the way Beyond is labeled doesn't do much good. It's
labeled for use too early. It needs to be sprayed after flooding when red
rice is emerging through the canopy and farmers notice it. I believe
(BASF is) working on expanding that label.

"However, since it's the same (type of chemistry as Newpath) it won't be
effective against hybridized red rice. If you've got tolerant red rice
and it came through two applications of Newpath, Beyond isn't going to
get it either."

What's your reaction to reports of illegally planted Clearfield rice?

"I haven't looked at any of those fields. Obviously, the growers wouldn't
have taken the risk and planted it if red rice hadn't already been there.
Besides being flat-out illegal, if they had any escapes at all, that's
real trouble.

"It's hard to police something like this. Brown-bagging seed is one
thing. But there's also those few outlaw farmers saying, 'Last year, this
technology worked great on my back 40 acres. I'm going to plant it again
on the same spot now. No one will see it back there.'

"That's not supposed to happen either. Crop rotation is the best way to
keep Clearfield viable.

"I have sympathy for producers who lease land that's a mess. They say,
'It's all red rice and I can't afford to grow soybeans on it. I'm going
to ride the Clearfield horse until it drops dead. After that, I'll let go
of the land.'

"But while I sympathize, that doesn't make it right. That scenario is
just as scary as brown-bagging. And I suspect that's happening more than
folks brown-bagging seed.

"By doing these things, we're shortening the life of this technology. We
can't afford that. There are no good red rice alternatives at hand --
Clearfield is all we've got. They may come up with Roundup Ready rice in
the future, but it isn't imminent and farmers shouldn't be planning for it."


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