METHOD OF IMPROVING THE YIELD OF HERBICIDE-RESISTANT CROP PLANTS

METHODE POUR AMELIORER LE RENDEMENT DE PLANTES CULTIVEES RESISTANT AUX HERBICIDES

English Abstract

Method of improving the yield of crop plants which are
resistant to glutamine synthetase inhibitors, in which
plants are treated with glutamine synthetase inhibitors
at low application rates, and to the use of glutamine
synthetase inhibitors for improving the yield of
transgenic crop plants.

French Abstract

Procédé pour l'accroissement du rendement de plantes utiles résistant aux inhibiteurs de la glutamine-synthétase, caractérisé en ce que les plantes sont traitées avec de faibles quantités d'inhibiteurs de la glutamine-synthétase. L'invention a également pour objet l'utilisation des inhibiteurs de la glutamine-synthétase pour l'accroissement du rendement de plantes utiles transgéniques.

Claims

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CLAIMS:
1. A method of improving yield of crop plants which
are resistant to glutamine synthetase inhibitors, which
comprises treating the crop plants with at least one
glutamine synthetase inhibitor at an application rate which
is not harmful to the plants.
2. The method as claimed in claim 1, wherein
glufosinate and salts thereof are employed for the yield-
improving treatment of crop plants which are protected
against the herbicidal property of the glutamine synthetase
inhibitor by expression of an n-acetyl-transferase gene.
3. The method as claimed in claim 1 or claim 2,
wherein the crop plants are treated at least once with the
active substance at an application rate as also employed for
weed control.
4. The method as claimed in any one of claims 1 to 3,
wherein the crop plants are treated at least once using
150-1000 g of glufosinate/ha.
5. The method as claimed in any one of claims 1 to 3,
wherein the crop plants are treated at least once using
350-700 g of glufosinate/ha.
6. Use of a glutamine synthetase inhibitor for
improving yield of crop plants which are resistant to this
inhibitor.

Description

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Description
Method of improving the yield of herbicide-resistant crop
plaata
The compound glufoainate (glufoaiaats-aa~oaivm, ammonium
DL-ho~moalania-4-yl(methyl)phosphiaate, Schwerdtle et al.,
Z. Pflanzenks. Pflanzenachutz., 1981, Special $ditioa IX,
page 431) acts as a glutamiae syathetass (GS) inhibitor
since it is a structural analog of glutamic acid. GS
playa a central role in the metabolism of all plaata. It
is responsible for the detoxification of NH3 ia, sad, as
a consequence, all terrestrial plants are damaged
severely or destroyed after application of glufoainate
since the asaimilatioa of a~aoaia is inhibited.
Plants which are resistant to the herbicidal activity of
GS inhibitors were successfully produced by traaaferriag
and exprea.aing a glufosinate acetyltransferaae geese
isolated from frown straiaa of Streptcanycetea which
produce bialaphos (phoaphiaothricia-alaayl-alaaiaa) (8B-
B1-0 Z4Z 236 and EP-81-D Z57 542). Stands of such trane-
a0 geaic, herbicide-tolerant crop plants can be kept weed-
free is as efficient manner by post-emergence treatment
with glucoaiaate.
Unexpectedly, field trials with such traaagnaic plants
showed that the glufoaiaate-treated plaata give a
measurably higher yield than untreated pleat staada. This
higher yield is not a result of the excellent weed
control by glufosinate sad its complete compatibility
with the ataada of traaageaic crop plaate, but a positive
effect of the herbicide treatment on growth sad yield.
The inveatioa therefore relates to a method of improving
yield of crop plants which are resistant to glutamine
synthetase inhibitors, which comprises treating the crop
plants with at least one glutamine synthetase inhibitor at
an application rate which is not harmful to the plants.

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In particular, the invention relates to a method in which
glutamiae aynthetaae inhibitors are employed for a yield-
improviag treatment of pleats which are protected against
the herbicidal activity of the glutamiae syathetase
inhibitor by expression of an N-acetyltransferase gene.
The invention furthermore relatos to the use of a glut-
amine synthetaae inhibitor for improving the yield of
crop plants which are reeiataat to this inhibitor. In
particular, it relates to the use of glutamiae ayathetase
inhibitors for improving the yield of traasgenic crop
plants.
The glutamine syathetase inhibitor used is preferably the
comipound glufosinata or bialaphoa (Tachibana et al.,
Abatr. 5th Int. Coagr. Pestic. Chem., IVs, Abstract 19;
Mace, Jpn. Pestic. Inf., 1984, No. 45, p. Z7) . In this
context, the-texm glufosinate embraces the racemats (DL-
homoalanin-4-yl(methyl)phoephinic acid gas wall as the
biologically active L isomor and the corresponding salts .
The herbicide can be employed in the commercially avail-
able formulations. A further example of a GB inhibitor is
the compound phosalacin (Omurs et al., J. of Antibiotics,
Vol. 37, 8. pages 939-940, 1984).
The yield-improving effect of the treatment with glufoa-
inate ie particularly pronounced whey the herbicidal
treatment is carried out is the 2 to 8-, preferably the
3 to 6-leaf stage of the crop plants before flowering or,
is the case of perennial plaata, at nay desired point in
time.
In the method according to the invention, the pleats are
treated at least once with the herbicide at application
rates as they are also employed for weed control, for
example 150 g - 1000 g of glufoeinate/ha.
However, the application rate required may vary as a
function of the plants. their height sad the climatic

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conditions.
It is particularly advantageous to carry out the process
using application rates of 350 - 700 g of glufosinate/ha.
Within this range of application rates, the affect
achieved is proportional to the application rate of
glufosinate, but not based on differences in the level of
weed control. It is possible to achieve a weed control
effect which is similar to the effect which can be
achieved at higher application rates even when the
application rate of PTC is low.
It is particularly advantageous to treat the plants
repeatedly with low dosages in the lower range of the
application concentrations, the treatment interval being
a few days, i.e. between 2 and 30 days, preferably
between 5 and 20, particularly preferably between 8 and
15 days. It is particularly advantageous to treat the
plants with low dosages, the treatment interval being
from 9 to 11 days.
The method according to the invention caa generally be
used for the treatment of plants which are resistant to
GS inhibitors. Resistant plants can also be obtained by
conventional breeding methods. If the resistance level of
plant obtained by conventional selection is similar to
that of the transgenic plants, the plants obtained by
conventional selection can also be treated by the method
according to the invention. However, the method is
particularly suitable for the treatment of glufosiaate-
resistant plants which have been obtained by transferring
a gene for resistance to the herbicide. EP-B1-0 242 236
and EP-H1-0 257 542 describe methods for producing such
plants.
In this context, the term plants embraces crop plants
from the group of the angiosperms and the gymnosperms.
The method according to the invention allows individual
plants, but also crops of pleats, to be treated.

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Particularly interesting among the gymnosperms is the
class of the conifers.
Particularly interesting among the angiosperms are the
plants from the families of the Solanaceae, Cruciferae,
Compositae, Liliaceae, Vitacese, Chenopodiaceae, Ruta-
ceae, Bromeliacese, Rubiaceae, Theaceae, Musaceae or
Gramineae and the order of the Leguminosae. Represen-
tatives of the families Solanaceae, Cruciferae and
Graminese are preferably treated.
The method is of particular interest for the treatment of
crop plants is which high yields are important, such as,
for example, maize, soybeans. spring and winter oil seed
rape, sugar beet, lucerne, sunflower, cotton, potatoes,
wheat, barley and rice. However, it can also be used
advantageously in tomatoes and other vegetables, such as
cucumber, and fruits, such as melon, strawberries,
raspberries, and kiwi fruit.
The use of the method in herbicide-resistant woody
species is also particularly important, for example in
plantations and nurseries.
Application of GS inhibitors, such as, for example, PTC
and its analogs and derivatives, to young specimens of
woody species can accelerate the juvenile development. In
this context, mention must be made, in particular, of
walnut trees, oil palms, fruit trees, poplars and other
cultivated plants which are woody species.
The method according to the invention ie therefore
important both in agriculture and horticulture since
application of the herbicidal glutamine synthetase
inhibitor allows a clearly measurable increase in yield
to be achieved without an additional application of
fertilizer and plant growth regulators. The term increase
in yield means in this context that the plant yield up to
50% more. Herbicides having different mechanisms of

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action either do not show such an effect or, frequently,
have an adverse affect on yield.
The growth-enhancing activity of the glufosinate treat-
ment can be measured is field trials and pot trials, by
comparing yields of stands of plants which are treated
with conventional herbicides or which were kept free from
weeds by non-chemical methods.
The examples which follow are intended to illustrate the
invention without thereby imposing any restriction.
IO Example 1
Transgenic glufosiaate-tolerant maize or soybean plants
were planted in plots (10 m2) and, in the 3 - 5 leaf
stage, treated with various amounts of glufosinate. The
weed control level was scored 42 days after the applica-
tioa. When the crops were ripe, the plots were harvested,
and the seed yield was determined by weighing the kernels
obtained.
When the maize plants were examined, Laddock~ (a mixture
of atrazine and bentazone) wan employed as comparison
product. Two products were employed for the treatment of
the soya bean plants. Comparison product 1 contained a
mixture of 134 g of fenoxaprop-P-ethyl/ha and 425 g of
fomesafen/ha; comparison product 2 contained 2240 g of
metolachlor/ha and 840 g of Storm~ (a mixture of benta-
zone and acifluorfen)/ha. The comparison products are
known from "The Pesticide Manual", 9th Edition, Hrit.
Crop Prot. Council, 1991.
The treatment described in Table 2, in which two low
glufosinate dosage rates were used, was carried out at a
10 day interval.

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Table 1
Application Co~ariscai
rates
of
Comparison product
glufosinate
(g of
active
substance/ha)
150 450 650 i
i
Weed control 92 97 98 78 t
level in %
Yield in % of 118 121 125 100
the plot with
the comparison
product

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