GB1603896A - Method for the agricultural production of ergot using chemical gametocides - Google Patents

Abstract

Before inoculating with ergot spores, a chemical gametocide is applied to the graminaceous plant in a sufficient quantity to cause an appreciable sterility of the plant. It was observed that the treatment with the gametocide led to ergot production with high yields. It is known that ergot alkaloids have medicinal uses.

Description

(54) A METHOD FOR THE AGRICULTURAL PRODUCTION OF ERGOT USING CHEMICAL GAMETOCIDES (71) We, ROHM AND HAAS COMPANY, a corporation organised under the laws of the State of Delaware, United States of America, of Independence Mall West, Philadelphia, Pennsylvania 19105, United States of America, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention concerns a method for the agricultural production of ergot using chemical gametocides.

Ergot, the sclerotium of the parasitic fungus Claviceps purpurea, has historically been an insidious pest in the cultivation of cereal crops. However, in recent years the development of many useful therapeutic drugs from ergot alkaloids has made its production not only desirable but also commercially attractive. While ergot can be grown in vitro, most of the ergot used in drug production comes from its agricultural cultivation, primarily in rye. Since ergot yields from such cultivation are usually about 50 to 200 kg./ha and the total alkaloid content of this ergot usually ranges between only 0.1 and 0.3 percent, methods for enhancing the yield of ergot or the quantity of ergot alkaloids produced in each plant would be particularly desirable.

The ergot fungus goes through a three-phase life cycle. In the first stage, fungal ascospores carried by the wind or by insects attack the ovaries of gramineous plants, which when infected produce "honeydew", a liquid exudate containing ergot conidiospores (conidia). The conidia are then transferred usually by insects to other ovaries in the same or a different plant or from wild plants to cultivated grain crops. From the infection of the conidia, the fungus enters a second stage, the production of a dark violet or purplish black mass referred to as the sclerotium. It is the sclerotium which is harvested and from which the ergot alkaloids are extracted. Finally, the sclerotia which are not harvested fall to the ground, and thereafter germinate to produce the fruiting bodies from which the ascospores are discharged.

In the commercial production of ergot, the infection of the ovaries of the host plant is carried out by directly applying to the flowers of the plant a suspension of conidia, usually in water. After development of the sclerotia, harvesting can them be carried out by hand or by conventional mechanical harvesting methods capable of separating the mature grain from the ergot sclerotia.

It has now been found that the agricultural production of ergot can be improved by applying a chemical gametocide to the gramineous host plant prior to infecting the plant with the ergot conidia.

In accordance with the invention there is provided a method for the agricultural production of ergot by infecting a gramineous plant with ergot spores, allowing the sclerotia to develop and harvesting the mature ergot sclerotia, which comprises applying to the plant prior to infection with the ergot spores at least one chemical gametocide in an amount effective to produce significant sterility in the plant, wherein said chemical gametocide is a compound of Formulae I - III set forth in the following description.

Formula I compounds are 1-arylpyridffiones of the formula

wherein R5 is a (C1-C4)alkyl group, R6 is an unsubstituted phenyl group or a substituted phenyl group having up to 3 substituents, preferably selected from halogen atoms, (C1-C4)alkyl groups, most preferably methyl, (C1-C4)alkoxy groups, most preferably methoxy, trifluoromethyl groups, and nitro groups, R7 is a hydrogen atom or a (C1-C4)alkyl group, R8 is a hydrogen atom, a (C1-C4)alkyl group, or a halogen atom, and Y1 is an amino group, a (Cl-C4)alkyl- or di(C1-4)alkylamino group, a hydroxy group, or an agronomically-acceptable salt thereof, or a (Cl-Cl2)alkoxy group, Formula I compounds are the subject of our UK Application No. 21918/77 (Serial No.

157592)5.

Formula II compounds are 1-aryl-4-pyridazinones of the formula

wherein Y3 is a hydroxy group, or an agronomically-acceptable salt thereof, or a (C1-C4)alkoxy R9 is an unsubstituted phenyl group or a substituted phenyl group having up to 3 substituents, preferably selected from halogen atoms, (C1-C4)alkyl groups, most preferably methyl, (C1 -C4)alkoxy groups, most preferably methoxy, and tri fluoromethyl groups, Rl is a (C1-C4)alkyl group, and R11 is a hydrogen atom, a (C1-C4)alkyl group, or a halogen atom.

Formula II compounds are the subject of our U.K. Application No. 7638/78 (Serial No.

1596611).

Formula III compounds are 1-arylpyrid-2-ones of the formula

wherein Y4 is a hydroxy group, or an agronomically-acceptable salt thereof, or a (C1-C4)alkoxy group, Rl2 is a (C1-C4)alkyl group, R13 is an unsubstituted phenyl or naphthyl group or a substituted phenyl group having up to 2 substituents, preferably selected from halogen atoms, (C1-C4)aleyl groups, most preferably methyl, (C1 -C4)alkoxy groups, most preferably methoxy, tn fluoromethyl groups, and nitro groups, Rl4 is a hydrogen atom, a (C1-C4)alkyl group, or a halogen atom, and Rl5 is a hydrogen atom or a (C1-C4)alkyl group.

Formula III compounds are the subject of our UK Application No. 23085/78 (Serial No.

1596887).

Typical gametocides which may be used are: N-(4-chlorophenyl) -3-carboxy-2,6-dimethylpyrid-4-one N-(4-fluorophenyl)-3-carboxy-2,6-dimethylpyrid-4-one N-phenyl-3-carboxy-2,6-dimethylpyrid-4-o N- (4-bromophenyl-3-carboxy-2 , 6-dimethylpyrid-4-one N-(3-chlorophenyl) -3-carboxy-2,6-dimethylpyrid-4-one N-(4-trifluoromethylphenyl)-3-carboxy-2,6-dimethylpyrid-4-one N-phenyl-5-bromo-3-carboxy-2 , 6-dimethylpyrid-4-one 1-phenyl-1,4-dihydro-4-oxo-6-methylpyridiazinone-3-carboxylic acid 1-(4-chlorophenyl)-1,4-dihydro-4-oxo-6-methylpyridazinone-3-carboxylic acid 1- 4-bromophenyl)-1 ,4-dihydro-4-oxo-6-methylpyridazinone-3-carboxylic acid 1 - 3-chlorophenyl)-1 ,4-dihydro-4-oxo-6-methylpyridazinone-3-carboxylic acid 1-(4-trifluoromethylphenyl)-1,4-dihydro-4-oxo-6-methylpyridazinone-3-carboxylic acid Ethyl 1-phenyl-1,4-dihydro-4-oxo-6-methylpyridazinone-3-carboxylate Ethyl 1-(4-chlorophenyl)-1,4-dihydro-4-oxo-6-methylpyridazinone-3-carboxylate 1-4-chlorophenyl -5-carboxy-4,6-dimethylpyrid-2-one 1-(4-bromophenyl)-5-carboxy-4,6-dimethylpyrid-2-one 1-(3,4-dichlorophenyl)-5-carboxy-4,6-dimethylpyrid-2-one Ethyl l-(4-bromophenyl)-4 1- 4bromophenyl)A,6-dimethylpyrid-2-one-5-carboxylate Ethyl 1- 4-chlorophenyl)-4,6-dimethylpyrid-2-one-5-carboxylate Additional chemical gametocides which can be used in the practice of the present invention include gibberellins, auxins, morphactins, maleic hydrazide, sodium 2,3dichloroisobutyrate, naphthalene acetic acid and derivatives, 2,3,5-triiodobenzoic acid, 2-chloroethylphosphoric acid, 3-(4-chlorophenyl)-6-methoxy-5-triazine-2,4-(1H ,3H)dione, and the like. Mixtures of these chemical gametocides can also be employed.

The chemical gametocides can be applied to the ergot host plant in any amount which will produce significant sterility in the plant. Preferably, about 60% or more male or female sterility, or both, will be most advantageous. Generally, the desired level of sterility will be obtained by applying the chemical gametocide to the host plant at a rate of about 1/32 to about 20 pounds per acre, and preferably about 1/16 to about 8 pounds per acre. The rate of application will vary depending on the host plant being treated, the chemical gametocide being applied, the time of treatment, and related factors. The obtainment of both male and female sterility is particularly advantageous.

A preferred method of applying the chemical gametocide is by foliar application. When this method is employed, sterility is generally most effectively induced when the gametocide is applied between flower initiation and meiosis. The chemical gametocide can also be applied as a seed treatment by soaking the seed in a liquid formulation containing the gametocide or by coating the seed with the compound. In seed treatment applications, the gametocide will generally be applied at a rate of about 1/4 to about 10 pounds per hundredweight of seed.

A wide variety of gramineous plants can be employed as the host plant. Among the preferred plants are the cereal grains, such as wheat, including durum, rye, triticale, and the like. One of the advantages of the present invention is that wheat, not normally susceptible to heavy infestation by ergot using conventional methods, is quite suitable for producing good yields of ergot by the method of the present invention. Not only does wheat have a high inherent capacity for ergot infection, it also resists lodging better than rye, the conventional host plant, thereby facilitating harvesting, and produces heavier, more compact ergot sclerotia. Generally, the chemical gametocide first will be applied to the host planet, preferably prior to flowering, and the host plant will be inoculated with ergot spores by any conventional procedure, subsequently, preferably at the time of or soon after flower opening. After the ergot has been allowed to mature, it can be harvested by conventional procedures.

The chemical gametocide can be applied to the plants to be treated either by itself or, as is generally done, as a component in an agriculutral composition or formulation which also comprises an agronomically-acceptable carrier. By "agronomically-acceptable carrier" is meant any substance which can be used to dissolve, disperse, or diffuse the chemical gametocide in the composition, without impairing its effectiveness and which by itself has no significant detrimental effect on the soil, equipment, crops, or agronomic environment.

Mixtures of chemical gametocides may also be used in any of these formulations. The compositions can be either solid or liquid formulations or solutions. For example, the chemical gametocides can be formulated as wettable powders, emulsifiable concentrates, dusts, granular formulations, aerosols, or flowable emulsion concentrates. In such formulations, the active compounds are extended with a liquid or solid carrier and, when desired suitable surfactants are incorporated.

It is usually desirable, particularly in foliar applications, to include adjuvants, such as wetting agents, spreading agents, dispersing agents, stickers, adhesives, and the like, in accordance with agricultural practices. Examples of adjuvants which are commonly used in the art can be found in the John W. McCutcheon, Inc. publication "Detergents and Emulsifiers Annual." The chemical gametocides can be dissolved in any appropriate solvent. Examples of solvents which are useful in the practice of this invention include water, alcohols, ketones, aromatic hydrocarbons, halogenated hydrocarbons, dimethylformamide, dioxane, dimethyl sulfoxide, and the like. Mixtures of these solvents can also be used. The concentration of active ingredient in the solution can vary from about 2% to about 98% by weight with a preferred range being about 20% to about 75%.

For the preparation of emulsifiable concentrates, the active compound can be dissolved in organic solvents, such as benzene, toluene, xylene, methylated naphthalene, corn oil, pine oil, o-dichlorobenzene, isophorone, cyclohexanone, methyl oleate, or in mixtures of these solvents, together with an emulsifying agent or surfactant which permits dispersion in water. Suitable emulsifiers include, for example, the ethylene oxide derivatives of alkylphenols or long-chain alcohols, mercaptans, carboxylic acids, and reactive amines and partially esterified polyhydric alcohols. Solvent-soluble sulfates or sulfonates, such as the alkaline earth salts or amine salts of alkylbenzenesulfonates and the fatty alcohol sodium sulfates, having surface-active properties can be used as emulsifiers either alone or in conjunction with an ethylene oxide reaction product. Flowable emulsion concentrates are formulated similarly to the emulsifiable concentrates and include, in addition to the above components, water and a stabilizing agent such as a water-soluble cellulose derivative or a water-soluble salt of a polyacrylic acid. The concentration of the active ingredient in emulsifiable concentrates is usually about 10% to 60% by weight and in flowable emulsion concentrates this can be as high as about 75%.

Wettable powders suitable for spraying, can be prepared by admixing the chemical gametocide with a finely divided solid, such as clays, inorganic silicates and carbonates, and silicas and incorporating wetting agents, sticking agents, and/or dispersing agents in such mixtures. The concentration of active ingredients in such formulations is usually in the range of about 20% to 98% by weight preferably about 40% to 75%. A dispersing agent may generally constitute about 0.5% to about 3% by weight of the composition, and a wetting agent may generally constitute from about 0.1% to about 5% by weight of the composition.

Dusts can be prepared by mixing the chemical gametocides with finely divided inert solids which may be organic or inorganic in nature. Materials useful for this purpose include, for example, botanical flours, silicas, silicates, carbonates and clays. One convenient method of preparing a dust is to dilute a wettable powder with a finely divided carrier. Dust concentrates containing about 20% to 80% by weight of the active ingredient are commonly made and are subsequently diluted to about 1 o to 10% by weight use concentration.

Granular formulations can be prepared by impregnating a solid such as granular fuller's earth, vermiculite, gound com cobs, seed hulls, including bran or other grain hulls, or similar material. A solution of one or more of the active compounds in a volatile organic solvent can be sprayed or mixed with the granular solid and the solvent then removed by evaporation. The granular material can have any suitable size, with a preferable size range of 16 to 60 mesh (U.S. Standard Sieve Series). The active compound will usually comprise about 2 to 15% by weigbt of the granular formulation.

Salts, such as sodium, potassium, lithium, calcium, magnesium, ammonium, substituted ammonium salts, and the like, of the chemical gametocides can be formulated and applied as aqueous solutions. The salt will typically comprise about 0.05 to about 50% by weight, preferably about 0.1% to about 10 o, of the solution. These compositions can also be further dlluted with water if desired prior to actual application. In some applications, the activity of these compositions can be enhanced by incorporating into the composition an adjuvant such as glycerin, methylethylcellulose, hydroxyethylceliulose , polyoxymethylenesorbitan monooleate, polypropylene glycol, polyacrylic acid, polyethylene sodium malate, polyethylene oxide, or the like. The adjuvant will generally comprise about 0.1 to about 5% by weight, preferably about 0.5 to about 2%, of the composition. Such compositions can also optionally include an agronomically-acceptable surfactant.

The chemical gametocides can be applied as sprays by methods commonly employed, such as conventional hydraulic sprays, aerial sprays, and dusts. For low-volume applications a solution of the active compound is usually used. The dilution and volume of application will usually depend upon such factors as the type of equipment employed, the method of application, the area to be treated and the type and stage of development of the crop being treated.

The following example will further illustrate the use of chemical gametocides in the agricultural production of ergot but are not intended to limit the invention in any way.

The following procedures are used for evaluating chemical gametocides in agricultural ergot production.

Test plantings of wheat, durum, and triticale are treated with the chemical gametocide during the stem extension period (between stage 8 and stage 9 on the Feekes scale). In a typical treatment, there is used an aqueous formulation of the chemical gametocide sodium N-(4-bromophenyl)-4,6-dimethyl-pyrid-2-one-5-carboxylate in a carrier volume of 500 liters/ha. containing a surfactant, such as about 0.03% by weight of Triton X-100, Triton being a registered trade mark. The concentration of the chemical gametocide is set to give an application rate of about 1 to 2 kg/ha. The composition is then sprayed onto the test plants using conventional techniques.

When a significant percentage spaying of the flowers of the test plants have an opened, the plants are inoculated with ergot spores by 1 spraying a suspension of ergot conidia with an atomizer, preferably directly on the opened flowers. If possible, the spraying is carried out during hot, humid weather to insure effective inoculation of the flowers with the conidia.

One convenient method for preparing the conidial suspension used in the inoculation is that described by Campbell, Canad. J. Botany, 35 (1957). Ergot sclerotia which have been sterilized by shaking for 30 seconds in a 0.1% aqueous mercuric chloride solution are rinsed in sterile water and cut into small pieces with a sterile knife. The pieces are plated out on an acidified medium, prepared from 10 g dextrose, 5 g malt extract, 5 g yeast extract, 20 g agar, and 1 liter water. When mycelia have begun to grow out of the ergot fragments, they are transferred to slants of potato dextrose agar for sporulation. The spores are then collected and formulated in water to give an optimum concentration of 105 conidia/ml. If desired, 2% sucrose can also be included in the conidial formulation to improve transfer of the ergot spores between plants by insects.

Within about three weeks after inoculation, significant growth of ergot sclerotia has occurred. Upon maturity, the sclerotia can be conveniently harvested with a combine and separated from the cereal grains by hand or by conventional mechanical means. High yields of ergot are obtained from this treatment, with up to 10 sclerotia per plant varying in weight from about 50 mg to about 650 mg.

WHAT WE CLAIM IS: 1. A method for the agricultural production of ergot by infecting a gramineous plant with ergot spores, allowing the sclerotia to develop and harvesting the mature ergot sclerotia which comprises applying to the plant prior to infection with the ergot spores at least one chemical gametocide in an amount effective to produce significant sterility in the plant, wherein said chemical gametocide is a compound of Formulae I - III set forth in the preceding description.

2. A method according to Claim 1, wherein the chemical gametocide is applied at a rate of 1/32 to 20 pounds per acre.

3. A method according to Claim 1, wherein there is used as gametocide the compound N-(4-bromophenyl)-4,6-dimethylpyrid-2-one-5-carboxylic acid or an agronomically acceptable salt thereof.

4. A method according to any preceding claim, wherein the plant is a cereal grain.

5. A method according to Claim 4, wherein the plant is wheat, durum or triticale.

6. A method according to Claim 1, wherein the gametocide effects significant male and female sterility in the plant.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (7)

**WARNING** start of CLMS field may overlap end of DESC **. adjuvant such as glycerin, methylethylcellulose, hydroxyethylceliulose , polyoxymethylenesorbitan monooleate, polypropylene glycol, polyacrylic acid, polyethylene sodium malate, polyethylene oxide, or the like. The adjuvant will generally comprise about 0.1 to about 5% by weight, preferably about 0.5 to about 2%, of the composition. Such compositions can also optionally include an agronomically-acceptable surfactant. The chemical gametocides can be applied as sprays by methods commonly employed, such as conventional hydraulic sprays, aerial sprays, and dusts. For low-volume applications a solution of the active compound is usually used. The dilution and volume of application will usually depend upon such factors as the type of equipment employed, the method of application, the area to be treated and the type and stage of development of the crop being treated. The following example will further illustrate the use of chemical gametocides in the agricultural production of ergot but are not intended to limit the invention in any way. The following procedures are used for evaluating chemical gametocides in agricultural ergot production. Test plantings of wheat, durum, and triticale are treated with the chemical gametocide during the stem extension period (between stage 8 and stage 9 on the Feekes scale). In a typical treatment, there is used an aqueous formulation of the chemical gametocide sodium N-(4-bromophenyl)-4,6-dimethyl-pyrid-2-one-5-carboxylate in a carrier volume of 500 liters/ha. containing a surfactant, such as about 0.03% by weight of Triton X-100, Triton being a registered trade mark. The concentration of the chemical gametocide is set to give an application rate of about 1 to 2 kg/ha. The composition is then sprayed onto the test plants using conventional techniques. When a significant percentage spaying of the flowers of the test plants have an opened, the plants are inoculated with ergot spores by 1 spraying a suspension of ergot conidia with an atomizer, preferably directly on the opened flowers. If possible, the spraying is carried out during hot, humid weather to insure effective inoculation of the flowers with the conidia. One convenient method for preparing the conidial suspension used in the inoculation is that described by Campbell, Canad. J. Botany, 35 (1957). Ergot sclerotia which have been sterilized by shaking for 30 seconds in a 0.1% aqueous mercuric chloride solution are rinsed in sterile water and cut into small pieces with a sterile knife. The pieces are plated out on an acidified medium, prepared from 10 g dextrose, 5 g malt extract, 5 g yeast extract, 20 g agar, and 1 liter water. When mycelia have begun to grow out of the ergot fragments, they are transferred to slants of potato dextrose agar for sporulation. The spores are then collected and formulated in water to give an optimum concentration of 105 conidia/ml. If desired, 2% sucrose can also be included in the conidial formulation to improve transfer of the ergot spores between plants by insects. Within about three weeks after inoculation, significant growth of ergot sclerotia has occurred. Upon maturity, the sclerotia can be conveniently harvested with a combine and separated from the cereal grains by hand or by conventional mechanical means. High yields of ergot are obtained from this treatment, with up to 10 sclerotia per plant varying in weight from about 50 mg to about 650 mg. WHAT WE CLAIM IS:

1. A method for the agricultural production of ergot by infecting a gramineous plant with ergot spores, allowing the sclerotia to develop and harvesting the mature ergot sclerotia which comprises applying to the plant prior to infection with the ergot spores at least one chemical gametocide in an amount effective to produce significant sterility in the plant, wherein said chemical gametocide is a compound of Formulae I - III set forth in the preceding description.

2. A method according to Claim 1, wherein the chemical gametocide is applied at a rate of 1/32 to 20 pounds per acre.

3. A method according to Claim 1, wherein there is used as gametocide the compound N-(4-bromophenyl)-4,6-dimethylpyrid-2-one-5-carboxylic acid or an agronomically acceptable salt thereof.

4. A method according to any preceding claim, wherein the plant is a cereal grain.

5. A method according to Claim 4, wherein the plant is wheat, durum or triticale.

6. A method according to Claim 1, wherein the gametocide effects significant male and female sterility in the plant.

7. Ergot when produced by a method according to any preceding claim.