Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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~L 2.d~ ~03~
S P E C I F I C A T I O N
METHOD FOR TREATING CEREAL CROP SEED WITH CHITOSAN
TO ENHANCE YIELD, ROOT GROWTH, AND STEM STRENGTH
Background of the Invention
One of the major problems in growing cereal crops
.
(defined as members of the grass family (Grami~ae) that produce
edible, starchy grains and .character.ized by long, narrow blades)
is the lodging (falling over) of plants prior to harvest, which
prevents the mechanical recovery at harvest of high yielding
plant heads. Researchers have tried to alleviate this problem
by:
1. Breeding stiffer stemmed varieties;
~: ~
2, Using chemical:treatments such as benzamidazole-
type fungicides (Benlate) to reduce root rot;
:~: : :: 3. Recommending that planting dates ~e delayed so that
:: there is a minimal time for organisms to initiate the root
:rotting:process pr~ior t~o the slow growth phase o~ winter, and
;:~ : 4.~ Recommending no-till or minimum tillage procedur~s
::: : :
: ~ that leave crop debris to redùce the erosion that is rampant when
plant:ing;;dates~:ar:e delayed.
Each~of these alternatlve procedures are partial solu-
tions to yield losses. However, each has serious drawbacks.
It has been impossible to breed for straw strength and
: still retain all of the other agronomic traits, e.g., winter
: hardiness, milling quality yield, disease resistance, etc., at
the same time because the high yielding heads place unusually
severe strain on the plant stem.
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Lodging has been reduced by fungicides that are deri-
vatives of methyl l-[butylcarbamoyl)-2-benzimidazole carbamate
(Benlate), which reduce the incidence of root rotting and thus
retain original straw strength. Extended use of this chemical,
however, has resulted in the selection of fungal pathogens that
are resistant to its fungicidal effect and, thus, effectiveness
is greatly diminished. Only e~ergency Food and Drug Administra-
tion clearance has been obtained for use of this chemical on
wheat because of potential side effects. Finally, its cost oF
treatment (approximately $7/acre~ is very high.
Delaying the planting date has reduced lodging; however
it prevents the time dependent development of large seedling
plants needed for ground cover prior to the onset of winter rains
and erratic snow melts that erode away large tonnages of soil
each year. The latter problem can be reduced by minimal tillage
:
practices that leave straw on top of the soil at planting time.
~owever, minimal tillage, which produces generally lower yields,
leaves weeds untilled as well and must be accompanied by addi-
tionaI herbicide and pesti~ide treatments requiring expensive
machinery for application.
Accordingly, there exists a need for a method that will
~:
~increase the straw strength and the root development oE cereal
crops at a commerclally feasible cost while still maintaining or
increasing the amount of yield.
: ~ '
Summary of the Invention
This invention describes a novel chitosan seed treatment
that strenghthens the stems of cereal crop plan~s, such as wheat,
helping to preserve their water-carrying capacity and greatly
reducing lodging (plants falling over before harvest), thus
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increasing yielcl. The lod~in~ problem is most severe ~hen seed
is plantecl early so that the plants can cover ~he qround prior
to t~e ~oil erocli~g wintex rains. Thus, by uslng thi~ seed
treatment, farmers will be able to plant crops early and reduce
the erosion loss that exceeds 10 tons per acre in some parts of
~he United States.
While ~his invention is applicable to any of the
cereal crops (e.q., barley, rye, oat~, atc.), prlmar~ worX has
been done wi~h wheat and this specification will discuss the
invention using wheat as an embodiment.
The problem of lodgin~ of hi~h yielding wheat plants
can be rectifled by ~eed treatment wlth the naturally ocaurrin~
carbohydrate, chitosan. Commercially produced chlto~an when
applied in an a~ueous form to whea* seeds is able, under ileld
conditions, to greatly increase the development of the plant's
root syste~, to substantially increase the diameter of the
stem, andl in association with these speci~ic and other
intangible, morphological and biochsmlcal develop~ents, to
enhanca yield. The chitosan kreatment results in a plant that
~0 is beneficial ~o erosion control, resistant to lodging, and
superior in yield over non-treated plants. The method of
treatment comprises the direct application of chitosan derlved
from various shell sources, such as crab, lobster, shrimp and
o~her marine life, in a nearly neutral agueous solution to
wheat seeds prior to planting.
Accordingly, it i~ a primary ob~ec~ o~ ~he present
invention to provide a me~hod for increasing the straw strength
and root developmen~ of cereal crops while increasing the
amount of yield.
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This and further object~ and advan~age~ will be
apparent to those skilled in the art in connecilon with the
detailed description o~ the preferred embodlments set forth
below.
.
lQ
~ 20:
:: ~
: ~0
3a
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16g/~90
DETAILED DESC~IPTION OF T~E PRE~ERRED EM~ODIMEMTS
Chitosan is a polymer made up of a hexosamine sugar
(glucosamine) whose molecules are linked (~1, 4) into chains that
can exceed molecular weights of one million. Chitosan compounds
in a range of up to and exceeding 1 x 106 molecular weight are
derived commercially from chitin. Chitin, an amino cellulose
derivite~, is the second most abundant polymer occurring in
nature, exlsting, for example, in the cell walls of fungi, bovine
cartilage, and the hard shells of insects and crustaceans.
Wastes from the shrimp, lobster, and crab seafood industries
contain 10-30% chitin. Chitosan is produced by deacetylating
chitin. This invention is effective if the deacetylation exceeds
90~ and it is most effective when approaching 100~ deacetylation.
Dry chitosan as either flakes, granules, or powder is
suitable as a starting material. The more finely dispersed the
chitosan, the more guickly it can be dlssolved in a dilute
aqueous acid (e.g., 1~ acetic acid or dilute hydrochloric acid,
sulfuric acid, or formic acid).
Typically, a quantity of chitosan suitable for planting
a~l60 acre field (quarter section) would be mixed as follows:
2.4 lbs. of crab shell chitosan is dissolved in 8 gallons of 1%
acetlc acid. 48 hours is allowed at room temperature for the
chitosan to dissolve with stirrlng. H20 is then added to bring
the volume to 26 gallons or until the viscosity is reduced enough
to feed~through the dispenser of commercial seed treating
machinery. (Most seed treatment machines utilized to handle
water based seed treatments can be utilized with the aqueous
solution of chitosan). The solution is neutralized to pH 6.0 to
6.5 with 0.2 to 0.23 gallons of 6.0 N NaOH. NaOH is added slowly
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with stirring, becau~e localized changes to a pH htgher than
7.G will c~use the chitosan to precipitate. Once near
neutrality, the viscosity of the opaque aqueous preparatiGn of
chitosan is reduced to the designed vlscosity with H20 to
approx1mately 26 gallons. From ~his, approximately 0.125
gallons is added to aach bushel of wh~at seed. This volume o~
aqueous chitosan increased the moisture percentage of 60 lbs.
of wheat seed by 1.6~.
Chitosan seed treatments were found to be effective
using rates ranglng from 60 ~y chitosan per gram of wheat seed
to 1000 ~g chitosan per gram of whPat seed. A preferred range
is from 225 ~g per gram of seed to 275 ~g per gram of seed.
Opttmal results were obtained at 250 ~g chitosan per gram o~
wheat seed. This rate is 0.014 lbs. chitosan per 60 lbs- ll
bushel) o~ wheat. Sixty pounds per acre is the averaye seeding
rate for wheat in most areas.
The native chitosan required to treat seed prior to
planting cost~ less than S.SO/acre. Chitosan treated seed can
be planted in late summer or as early in August as moisture is
available. The chitosan treatmen~ enhances s~tem diame~er by
approxima~ely 10%. Al~hough chitosan-treated plants grown in
soils heavily infested with root rotting disease are
susceptlble to development of some rotting sympto~s such as
stem disooloration and some white heads, the larger stem
diameter and the extensive roo~ system caused by the treatment
maintain greater stem strength and an adequate water
transpor~ing capacity o~ stem vascular systemg. As a result of
seed treatment with this na~urally occurrlng compound, 10-30%
higher ylelds are obtained at a low cost, soil erosion is
minimiæed, and the chltosan is readlly degraded to simple amtno
sugar resldues and/or metaboli~ed by soil organism~.
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Pl~n~s and mlcro-organisms contain chitosanase and
other degradative enzy~es with th~ potential to digest chitosan
into
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smaller fragments and eventually into hexosamines that can be
utilized as nutrients by soil microflo~a.
If seed is treated in a humid environment, a post-
treatment drying step must be added to reduce the moisture
content of the treated grain to the 10-14% range in order to
prevent premature germination of the seed; therefore, the more
viscous the chitosan preparation, the less drying that will be
required. Highly viscous chitosan preparations can be mixed with
wheat seed using any machinery marketed for cement mixing. Modi- -
fications of grain augering devices will also enable chitosan to
be added to wheat seed as it is being loaded aboard trucks just
prior to transport to the field for planting. This eliminates
the need for extensive drying to prevent seed germination.
Chitosan seed applications are not detrimentally in-
fluenced by fertilizer supplements, herbicide applications or
irrigation programs. Other commercial seed treatments, e.g.,
insec~tic~des and fungicides, can be applied prior to chitosan.
Components already on the seed will be attached to the seed by
the chitosan, which leaves a "cellophane-like" surface on seed
after drying. The chitosan~treated seed can be planted directly
n any commercial planter. Special planters that automatically
administer fertilizers, soil sterilantsl herbicides, etc. can be
utilized to treat seeds with chitosan as they are being planted.
Chitosan labelled with tritium, [3H]-Chitosan, added to seeds was
translocated to the developing plant indicating that a large
portion of the chemical is distributed systemically.
Dry chitosan can be stored indefini~ely at room tempe-
rature withou~ loss of biological activity. Chitosan can be
mixed as described above at room temperature. Chitosan has no
known toxicity and can be supplemental to the diet of animals
without detrimental side effects. The physical irritation pro-
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perties of chitosan have not been investigated in long termstudies, however, and, therefore, the same ~)asic precautions
taken in the handling of other fibrous materials or powders,
~ e.g., cotton fibers or flour, may apply to chitosan.
; The root enhancing, stem diameter increasing, and
strengthening effect of chitosan is seen at both early and late
seedinq dates; however, the major beneficial effects for erosion
reduction are obtained with early seeding dates. This allows the
development of the large seedling plants needed for ground cover
prior to the onset of winter rains and snow melts while the
chitosan minimizes the problem of root rotting.
The following data illustrate examples of enhanced
properties obtained, in this case, in wheat through the use of
this invention.
EXAMPLE 1. Enhanced Seedling Development
1:
1 ~
Seedlings from Chitosan treated Daws wheat seed (200 ~g
Chitosan/g seed) 4 months after planting at Washtuchna, Washing-
ton under circle irrigation, October 15, 1983.
~; Ave. diameter Ave. length Ave. wt.
Seed Treatment of crown o~ stem from root system
(lower stem) crown to first per 30
leaf plants
mm cm fresh wt dry wt
H20 control 2.3 3.7 1.002 .139
Chitosan
(200 ~g/g seed~ 3.7 3.8 2.690 .330
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EXAMPLE 2. Reduced Lodying
Daws winter wheat 1983 crop lodging
reading on outside row of 4' x 100' plot.
Treatment Stems lodaed
~9 Chitosan/gram seed No.
Chitosan 62 275
Control 468
Chitosan 125 313
Control 948
Chitosan 250 143
Control 835
Chitosan 500 186
Control 652
Chitosan 1000 250
Control 410
EXAMPLE 3. Increased Stem Diameter
Effect of chitosan seed treatment on stem diameter
of Daws whe:at at maturity - 1983
~ ~ '
Chitosan applied per gram seed Stem diametera % increase
~g mm
Chitosan 62 3.872a --
Control : 3.239 19
Chitosan 125 3.432 --
Control 3.231 6
Chitosa:n 250 3.606 --
Control 3.322 9
Chitosan 500 ~ 3.997 --
Control 3.651 9
::~ .
~:
~ aAverage diameter of 100 stems.
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EXAMPLE 4. Enhanced Yield
.
EfEect of Chitosan Seed Treatment on Daws
Winter Wheat Yield in 1983
.
CHITOSAN Avg. Bushel
Yield Increase increase
Per over
application cost bushels Acre control
lbs/bushel acre acre
: Chitosan 1000-~g/g wheat 059 $.soa90.2b 11.4 14
Control 78.8
Chitosan 500 ~g/g wheat .029 $.2589.7 10.9 13%
Control 77.8
Chitosan 250 ~g/g wheat .014 $~1294.3 16.5 21
Control 84.2
Chitosan 125 ~g/g wheat .007 $.0691.5 7~3 8
: a Dollar values were: chitosan (lbs)/60 lbs. seed
(planting rate/acre) x 160 acres x ~9.00/lb.
chitosan.
b Yield was an average of four replications. Plot
:: size was 4' x 30'. Lodging in control plots was up
to 60~. Yield included lodged wheat recovered by
hand at harvest.
EXAMPLE 5. Enhanced Yield
elder spring wheat treatment yield - ~ of control
: 1982
Chitosan (320 ug/g) seed
~ : treatment only 131
:~ Control - 100
:
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EXAMPLE 6. Enhanced Yield
Daws winter wheat treatment - 1982 yield - % of control
Chitosan (500 ~g/g) seed
treatment 107
Control lO0
: : EXAMPLE 7. Enhanced Disease Resistence
Effects of Chitosan Seed.Treatment
Daws Wheat Psuedocercosporella herpotrichoides
Disease symptoms on wheat straw at harvest
No. o~ Straws/Sympton Value Category
(Chitosan treatment and control)
:
Mature Stem Clean Slight Scattered Coalescing Diseased &
Symptoms Straw DiscoIoration Lesions _ Lesions __ Broken
:
Symptom
~: ~ Value~ ~ ~ : 0 ~ 1 2 3 4
--
6;2~:~g/g ~ 4 22 35 22 17
:
Control 8 28 40 24
125 ~/g 5 13 24 12 46
Control ~ l 8 21 49 21
250 ~g/g~: 2 15 19 48 18
Control ~ : 0 8 :: 39 48 5
500 ~g/g 7 L9 ;37 21 16
:Control 0 4 35 59 7
~::
lO00 ~9/g 0 8 32 55 5
Control 1 9 38 48
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Having fully described the present invention, it
will be apparent to those skilled in the art that modi-
fications to the method described herein may be made without
departing from the scope of the present invention. While
the embodiment described involves wheat, the process is
generally applicable to cereal crops. Only the wheat
embodiment has been included for the sake of brevity.
Therefore, the scope of this invention is not intended to be
limited except as may be required by the lawful scope of the
following claims.
:
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