CA1263038A

CA1263038A - Method for treating cereal crop seed with chitosan to enhance yield, root growth and stem strength

Info

Publication number: CA1263038A
Application number: CA000491652A
Authority: CA
Inventors: Lee A. Hadwiger
Original assignee: Washington State University Research Foundation
Current assignee: Washington State University Research Foundation
Priority date: 1984-10-05
Filing date: 1985-09-26
Publication date: 1989-11-21
Also published as: AU4796085A; AU583534B2

Abstract

ABSTRACT

METHOD FOR TREATING CEREAL CROP SEED WITH CHITOSAN
TO ENHANCE YIELD, ROOT GROWTH, AND STEM STRENGTH

Commercially produced chitosan applied to cereal crop seeds at rates of 60 µg to 1000 µg per gram of seed enhances root development, crown diameter, mature straw strength and crop yield. Dry chitosan, when dissolved in dilute acid and neutral-ized, is applied directly to cereal crop seed with only minor modification to seed treating machinery and methods. In addition to a clear benefit in cereal crop yield, the chitosan treated seed can be planted early to reduce erosion and it can be planted in regions having soil infested with root rotting organisms and not suffer extensive lodging that would prevent seed recovery by commercial harvesters.

Description

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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;
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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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~ 3~3~ 1~9/290 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 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.

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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 ~1 2~
73232~1 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~.

~ 2S~ 73232-1 Pl~n~s and mlcro-organisms contain chitosanase and other degradative enzy~es with th~ potential to digest chitosan into ~'~

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~6~3~3 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-~6~

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:
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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 ~ .

11 ~ 3 (~ ~3 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 ::~ .
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~ 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 :

~6~ 169/290 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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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A method of enhancing cereal crop yield, straw strength, stem diameter, and root development comprising:
applying chitosan in an effective amount to cereal crop seed.

2. The method of claim 1 wherein said chitosan is dissolved in a dilute aqueous acid prior to application.

3. The method of claim 1 wherein the rate of application is between 60 µg/g seed and 1000 µg/g seed.

4. The method of claim 1 wherein said cereal crop is wheat.

5. The method of claim 1 wherein said cereal crop is barley.

6. The method of claim 1 wherein said cereal crop is rye.

7. The method of claim 1 wherein said cereal crop is oats.

8. The method of claim 4 wherein the rate of application is between 225 µg/g wheat seed and 275 µg/g wheat seed.

9. The method of claim 5 wherein the rate of application is substantially 60 µg/g barley feed,

10. The method of claim 7 wherein the rate of application is between 75 µg/g oat seed and 225 µg/g oat seed.

11. Cereal crop seed treated with chitosan in an amount of between 60 µg/g seed and 1000 µg/g seed.

12. The product of claim 11 wherein said cereal crop is wheat.

13. The product of claim 11 wherein said cereal crop is barley.

14. The product of claim 11 wherein said cereal crop is rye.

15. The product of claim 11 wherein said cereal crop is oats.

16. A method of enhancing wheat yield, stem diameter, and root development in wheat plants comprising the step of applying chitosan in an effective amount to wheat seed prior to planting.

17. The method of claim 16, wherein the chitosan is dissolved in a dilute aqueous acid solution prior to application.

18. The method of either claim 16 or claim 17, wherein the rate of application of the chitosan is between 60 µg per gram of wheat seed and 1000 µg per gram of wheat seed.

19. The method of claim 16 or 17, wherein the rate of application of the chitosan is between 225 µg per gram of wheat seed and 275 µg per gram of wheat seed.

20. The method of claim 16 or 17, wherein the rate of application of the chitosan is about 250 µg per gram of wheat seed.

21. Wheat seed treated with chitosan in an amount effective to enhance yield, straw strength, stem diameter, and root development of wheat plants germinating from said wheat seed.

22. The product of claim 21 wherein the wheat seed is treated with chitosan in an amount between 60 µg per gram of wheat seed and 1000 µg per gram of wheat seed.

23. The product of claim 22 wherein the wheat seed is treated with chitosan in an amount between 225 µg per gram of wheat seed and 275 µg per gram of wheat seed.

24. The product of claim 22 wherein the wheat seed is treated with chitosan in an amount of about 250 µg per gram of wheat seed.

25. A method of enhancing wheat yield, straw strenyth, stem diameter, and root development in wheat plants comprising the step of applying chitosan in an effective amount to wheat seed, the chitosan being produced by deacetylating chitin to an extent exceeding 90%.

26. The method of claim 26 in which chitosan is applied to the wheat seed as a dilute neutralized aqueous acid solution of chitosan.

27. The method according to claim 25 in which the dilute aqueous acid for the solution of chitosan is selected from the group consisting of acetic acid, hydrochloric acid, sulfuric acid, and formic acid.

28. The method according to claim 26 in which the solution of chitosan is neutralized to a pH no greater than 7Ø

29. The method according to claim 27 in which the dissolved chitosan solution is neutralized to a pH of 6.0 to 6.5.

30. The method according to claim 26 in which the application of chitosan to the wheat seed leaves a cellophane-like surface on the wheat seed after drying.

31. The method according to claim 30 in which the rate of application of the chitosan 15 between 60 µg per gram of wheat seed and 1000 µg per gram of wheat seed.

32. The method according to claim 31 in which the rate of application of the chitosan is between 225 µg per gram of wheat seen and 275 µg per gram of wheat seed.

33. The method according to claim 32 in which the rate of application of the chitosan is about 250 µg per gram of wheat seed.

34. A method of enhancing wheat yield and preventing lodging of wheat plants comprising the steps of:
a. dissolving in a dilute aqueous acid solution, chitosan that has been produced by deacetylating chitin to an extent exceeding 90%, in order to form an aqueous acid solution of chitosan;
b. neutralizing the aqueous acid solution of chitosan to a pH no greater than 7.0;

c. coating wheat seed with the neutralized aqueous acid solution of chitosan; and d. drying the wheat seed to leave a cellophane-like surface of chitosan on the wheat seed.

The method according to claim 34 in which the rate of application of chitosan is between 60 µg per gram of wheat seed and 1000 µg per gram of wheat seed.

36. Wheat seed treated with chitosan by the method or claim 8.

37. An aqueous composition comprising:
chitosan which has been dissolved in a dilute aqueous acid and then neutralized.

38. The composition of claim 37 wherein said chitosan is dissolved by treating wastes from shrimp, lobster, and crustacean seafood industries having 10-30% chitosan in said dilute acid.

39. The composition o claim 37 wherein the dilute aqueous acid is acetic acid, dilute hydrochloric acid, sulfuric acid, or formic acid.

40. The composition of claim 37 wherein the chitosan has been deacetylated to an extent exceeding 90%.

41. The composition of claim 37 which is neutralized to a pH greater than 6.0 but less than 7.0 by the use of NaOH.

42. The composition of claim 41 wherein pH is between 6.0 and 6.5.

43. A method of preparing a chitosan solution comprising dissolving chitosan in a dilute aqueous acid solution and then adding a sufficient amount of a base to neutralize said solution to a pH greater than 6.0 but less than 7Ø

44. The method of claim 43 wherein the pH is between 6.0 and 6.5.

45. The method of claim 43 wherein the base is NaOH.

46. The method of claim 44 wherein the base if NaOH.

47. The method of claim 44 wherein the dilute aqueous acid is acetic acid, dilute hydrochloric acid, sulfuric acid, or formic acid.

48. The method of claim 44 wherein the chitosan has been deacetylated to an extent exceeding 90%.

49. A method of enhancing cereal crop yield, straw length, stem diameter, and root development, which method comprises applying an effective amount of a composition according to claim 37 to cereal crop seed.