JP7315912B2 - strigolactone biosynthesis inhibitor - Google Patents

Description

The present invention relates to biosynthetic inhibitors against strigolactones, which are plant hormones that regulate plant branching and the like.

Strigolactones promote the seed germination of Striga and Orobanche, which are root-parasitic plants that are a problem in food production in Africa, and increase the infestation of crops by parasitic weeds, and are symbiotic fungi. It is known as a plant physiologically active substance that induces hyphal branching of arbuscular mycorrhizal fungi (AM fungi) and promotes the absorption of phosphorus and water. Recently, it has been suggested that strigolactones and their metabolites function as plant hormones that control plant branching, and are attracting attention as substances responsible for the regulation of normal vegetative growth and subsequent reproductive growth. ing.

It is known that strigolactones are biosynthesized by carotenoid oxidative cleavage enzymes (CCD7 and CCD8) and cytochrome P450 monooxygenase, and that F-box proteins are involved in their signal transduction. has hardly been elucidated. As strigolactones, strigol, sorgomol, 5-deoxystrigol, and orbanchol are known, and as a synthetic strigolactone, GR24 is known. there is

Abamine (N-[3-3,4-dimethoxyphenyl]-2-propenyl)-N-(4-fluorobenzyl)glycine methyl ester is a substance that inhibits the biosynthesis of strigolactones. ) decreased 5-deoxystrigol and sorghum secretion in sorghum, and decreased 5-deoxystrigol secretion in rice. In addition, it has been suggested that brassinosteroid biosynthetic enzyme inhibitors and abscisic acid biosynthetic enzyme inhibitors may contain compounds with strigolactone biosynthesis inhibitory activity. The chemical structure has not been clarified).

The inventors also disclosed in JP 2013-56832 A that 2,2-dimethyl-7-phenoxy-4-(1H-1,2,4-triazole-1 -yl)heptan-3-one (MA39) and its derivatives can increase biomass in plants, especially rice and sugarcane, by increasing plant branching and promoting tillering in gramineous plants. We reported that it can be done (Patent Document 1).

JP 2013-56832 A

An object of the present invention is to provide a group of strigolactone biosynthesis inhibitors that are more active than hitherto reported strigolactone biosynthesis inhibitors.

The inventors of the present invention conducted intensive research to solve the above problems, and found that the compound represented by the following general formula (I) has an effect of increasing stems (tilling effect) on plants. The present inventors have found that the inhibitory effect on strigolactone biosynthesis is higher than the previously reported strigolactone biosynthesis inhibitory effect. The present invention has been completed based on the above findings.

Thus, according to the invention, the following general formula (I):

(Wherein, R ¹ represents a hydrogen atom, an alkyl group, a halogenated alkyl group, an alkoxy group, a carboxyl group, an aryl group, an aryloxy group, a hydroxyl group, an amino group, a nitro group, or a halogen atom; R ² and R ³ represents a combination of a hydroxyl group and a hydrogen atom, or ^R2 and ^R3 together represent an oxo group; _L1 is (CH2 ₎ 2 _- O-(CH2 ₎ 2 _- O or _CH2- CH═CH—CH ₂ —O ; R ⁴ is a hydrogen atom, an alkyl group, a halogenated alkyl group, an alkoxy group, a carboxyl group, an aryl group, an aryloxy group, a hydroxyl group, an amino group, a nitro group, or a halogen atom When R ¹ and R ⁴ are substituents other than hydrogen atoms, the number of substituents is 1 to 2. A strigolactone biosynthesis inhibitor comprising a compound represented by ) or a salt thereof is provided.

According to a preferred embodiment of the present invention, L ₁ is (CH ₂ )nO (n is an integer of 2 to 6), and R ⁴ is a hydrogen atom or is present at any position on the benzene ring. The above strigolactone biosynthesis inhibitor, which does not contain compounds or salts thereof that are 1 or 2 halogen atoms; The above strigolactone synthesis inhibitor, wherein R ¹ is a hydrogen atom; R ² and R ³ are together an oxo group _; Synthetic inhibitor; L ₁ is Ar ₁ -O-Ar ₂ -O (Ar ₁ and Ar ₂ are saturated or unsaturated linear alkylene, and the sum of the number of carbon atoms of Ar ₁ and Ar ₂ is 2 to 6) or Ar ₃ —O (Ar ₃ is a saturated or unsaturated linear alkylene having 1 to 7 carbon atoms). inhibitor; at least _L1 is selected from the group consisting of ( _CH2 ) _2- O-( _CH2 ) ₂ -O, CH2 _- CH=CH- _CH2 -O, or ( _CH2 ) ₄ -O A strigolactone biosynthesis inhibitor as described above is provided as a substituent.

Further, according to the present invention, a plant branching-increasing agent containing the above strigolactone biosynthesis inhibitor; a gramineous plant tillering promoter containing the above strigolactone biosynthesis inhibitor; a flower number-increasing agent comprising a strigolactone biosynthesis inhibitor; a biomass-increasing agent comprising the above strigolactone biosynthesis inhibitor; a crop yield-increasing agent comprising the above strigolactone biosynthesis inhibitor; Provided is a parasitic weed germination inhibitor comprising a ton biosynthesis inhibitor.

From yet another aspect, a method for inhibiting strigolactone biosynthesis in a plant, comprising the step of applying the compound represented by the above general formula (I) or a salt thereof to the plant; A method of increasing branching, comprising applying to a plant a compound represented by the above general formula (I) or a salt thereof; A method of promoting tillering in a gramineous plant, comprising: A method comprising the step of applying a compound represented by the general formula (I) of or a salt thereof to a gramineous plant; a method of increasing the number of flowers in a flowering plant by branching, wherein A method comprising the step of applying a compound represented by formula (I) or a salt thereof to a plant; A method for increasing biomass, the method comprising the step of applying a compound represented by the above general formula (I) or a salt thereof to a plant a method for increasing crop yield, comprising the step of applying a compound represented by the above general formula (I) or a salt thereof to a plant; a method for preventing germination of parasitic weeds, comprising: A method is provided comprising the step of applying a compound represented by general formula (I) or a salt thereof to a plant.

Further, according to the present invention, the above general formula (I) (wherein R ¹ is a hydrogen atom, an alkyl group, a halogenated alkyl group, an alkoxy group, a carboxyl group, an aryl group, an aryloxy group, a hydroxyl group, an amino group, a nitro group , or represents a halogen atom; R ² and R ³ represent a combination of a hydroxyl group and a hydrogen atom, or R ² and R ³ together represent an oxo group; L ₁ is linear or branched represents a substituent in which any discontinuous carbon atom of alkylene is replaced with an oxygen atom; ^R4 is a hydrogen atom, alkyl group, halogenated alkyl group, alkoxy group, carboxyl group, aryl group, aryloxy group, hydroxyl group, amino 6-(2 _{- methyl} phenoxy)-1-phenyl-2-(1H-1,2,4-triazol-1-yl)hexan-1-one (KK101); 6-(2,6-dimethylphenoxy)-1-phenyl-2- (1H-1,2,4-triazol-1-yl)hexan-1-one (KK102); 6-(3,6-dimethylphenoxy)-1-phenyl-2-(1H-1,2,4- Triazol-1-yl)hexan-1-one (KK103); 6-(4-Nitrophenoxy)-1-phenyl-2-(1H-1,2,4-triazol-1-yl)hexan-1-one (KK106); is at least one compound selected from the group consisting of; or a salt thereof.

The compound represented by the general formula (I) or a salt thereof has the effect of inhibiting the biosynthesis of strigolactone in plants, for example, increases plant branching and promotes tillering in gramineous plants. By doing so, it is possible to increase the biomass of plants, especially rice and sugar cane. In flowering plants, it is also useful in the horticultural field because it can increase the number of flowers by increasing branching. Furthermore, since it has a germination-inhibiting effect on parasitic weeds, it is possible to suppress the parasitism of parasitic plants on crops and increase the yield of crops.

FIG. 3 shows the effect of compound treatment on the amount of strigolactone secreted. FIG. 3 shows the effect of compound treatment on the amount of strigolactone secreted. FIG. 3 shows the effect of compound treatment on the amount of strigolactone secreted. FIG. 4 shows the effect of compound treatment on reducing the amount of strigolactone endogenous. FIG. 4 shows the results of gene expression changes in KK5-treated Arabidopsis thaliana. FIG. 4 shows increased branching in KK5-treated Arabidopsis thaliana. KK5 is a diagram showing that there is no inhibitory effect on gibberellin biosynthesis. KK5 is a diagram showing that there is no inhibitory effect on brassinosteroid biosynthesis. KK5, KK12, KK13, KK16, and KK18 have no inhibitory effect on gibberellin biosynthesis.

As used herein, the term "strigolactone" means a plant hormone that is biosynthesized by carotenoid oxidative cleavage enzymes (CCD7 and CCD8) and cytochrome P450 monooxygenase and has the effect of controlling plant branching. See Nature, 455, pp. 189-194, 2008 and Nature, 455, pp. 195-200, 2008. Strigolactones to be used as inhibitors of the present invention include naturally occurring strigolactones (e.g., strigols, sorgomols, 5-deoxystrigol, and orobanchol) as well as non-natural strigolactones (e.g., GR24 etc.), but are not limited to these.

The alkyl groups represented by R ¹ and R ⁴ may be saturated or unsaturated, and may be linear, branched, cyclic, or a combination thereof. The number of carbon atoms is about 1 to 6. A preferred example of the alkyl group is a methyl group. The alkyl group of the halogenated alkyl group represented by R ¹ and R ⁴ may be saturated or unsaturated, and may be linear, branched, cyclic, or a combination thereof. The number of carbon atoms is about 1 to 6. A preferable example of the halogenated alkyl group is a trifluoromethyl group. The alkyl group of the alkoxy group represented by R ¹ and R ⁴ may be saturated or unsaturated, and may be linear, branched, cyclic, or a combination thereof. The number of carbon atoms is about 1 to 6. A preferable example of the alkoxy group is a methoxy group. Examples of the aryl group represented by R ¹ and R ⁴ include a phenyl group and a naphthyl group, and preferably a phenyl group. One or more substituents such as an alkyl group, an alkoxy group, a hydroxyl group, an amino group and a carboxyl group may be present at arbitrary positions on the ring of the aryl group represented by R ¹ and R ⁴ . However, it may be an unsubstituted aryl group. Examples of the aryloxy group represented by R ¹ and R ⁴ include a phenoxy group and a naphthoxy group, with the phenoxy group being preferred. One or more substituents such as an alkyl group, an alkoxy group, a hydroxyl group, an amino group and a carboxyl group are present at arbitrary positions on the aryl ring of the aryloxy group represented by R ¹ and R ⁴ . However, it may be an unsubstituted aryl group. A halogen atom represented by R ¹ and R ⁴ may be a fluorine atom, a chlorine atom, a bromine atom or an iodine atom, preferably a fluorine atom, a chlorine atom or a bromine atom. When R ¹ and R ⁴ are substituents other than hydrogen atoms, the number of substituents is preferably 1-2 . Substitution positions of substituents other than hydrogen atoms are not particularly limited, and they can be substituted at arbitrary positions. When there are multiple substituents other than hydrogen atoms, those substituents may be the same or different.

The straight-chain or branched-chain alkylene moiety in the substituent in which any discontinuous carbon atom of the straight-chain or branched-chain alkylene represented by L ₁ is replaced with an oxygen atom may be either saturated or unsaturated. The length of the linear chain in the substituent in which any discontinuous carbon atom of the linear alkylene represented by L ₁ is replaced by an oxygen atom, any discontinuous carbon atom of the branched alkylene represented by L ₁ is replaced by an oxygen atom The length of the main chain of the substituted substituents is about 2 to 8 atoms. The branched chain length of the substituent in which any discontinuous carbon atom of the branched alkylene represented by L ₁ is replaced with an oxygen atom is about 1 to 4 atoms. Preferred examples of L ₁ include a substituent in which arbitrary discontinuous carbon atoms of linear alkylene are replaced with oxygen atoms. Furthermore, as a preferred example, Ar ₁ -O-Ar ₂ -O (Ar ₁ and Ar ₂ are saturated or unsaturated linear alkylene, and the sum of the number of carbon atoms of Ar ₁ and Ar ₂ is 2 6) or Ar ₃ —O (Ar ₃ is a saturated or unsaturated linear alkylene having 1 to 7 carbon atoms). Of these, ( _CH2 ) ₂ -O-( _CH2 ) ₂ -O, _CH2 -CH=CH- _CH2 -O, or ( _CH2 ) ₄ -O is particularly preferred.

The compound represented by the above formula (I) has at least one asymmetric carbon and may have one or more asymmetric carbons depending on the type of substituent. In addition to pure forms of optically active isomers or diastereoisomers based on the asymmetric carbon of the inhibitor of the present invention, any isomer mixture (e.g., a mixture of two or more diastereoisomers) or a racemate may be used as an active ingredient of

In addition, the compound represented by the above formula (I) can form an acid addition salt, and may form an acid addition salt depending on the type of substituent. The type of salt is not particularly limited, and includes salts with mineral acids such as hydrochloric acid and sulfuric acid, salts with organic acids such as p-toluenesulfonic acid, methanesulfonic acid and tartaric acid, and metal salts such as sodium salts, potassium salts and calcium salts. Salts, ammonium salts, salts with organic amines such as triethylamine, and salts with amino acids such as glycine can be mentioned. Furthermore, the compounds represented by formula (I) or salts thereof may exist as hydrates or solvates, and these substances may be used as active ingredients of the inhibitors of the present invention.

In the compound represented by the general formula (I), L ₁ is a compound that does not represent (CH ₂ )nO (n is an integer of 2 to 6), 6-(2-methylphenoxy)-1-phenyl- 2-(1H-1,2,4-triazol-1-yl)hexan-1-one (KK101), 6-(2,6-dimethylphenoxy)-1-phenyl-2-(1H-1,2, 4-triazol-1-yl)hexan-1-one (KK102), 6-(3,6-dimethylphenoxy)-1-phenyl-2-(1H-1,2,4-triazol-1-yl)hexane -1-one (KK103), 6-(4-nitrophenoxy)-1-phenyl-2-(1H-1,2,4-triazol-1-yl)hexan-1-one (KK106), is a novel compound is. Needless to say, any hydrates or solvates of these compounds or salts thereof as well as any salts of these compounds are included in the scope of the present invention.

Preferred compounds as active ingredients of the inhibitor of the present invention include, for example,
6-phenoxy-1-phenyl-2-(1H-1,2,4-triazol-1-yl)4-hexene-1-one (KK3);
4-(2-phenoxyethoxy)-1-phenyl-2-(1H-1,2,4-triazol-1-yl)butan-1-one (KK5);
4-[2-(2,6-dichlorophenoxy)ethoxy]-1-phenyl-2-(1H-1,2,4-triazol-1-yl)butan-1-one (KK12);
4-[2-(3-chlorophenoxy)ethoxy]-1-phenyl-2-(1H-1,2,4-triazol-1-yl)butan-1-one (KK13);
4-[2-(4-bromophenoxy)ethoxy]-1-phenyl-2-(1H-1,2,4-triazol-1-yl)butan-1-one (KK14);
4-[2-(4-methoxyphenoxy)ethoxy]-1-phenyl-2-(1H-1,2,4-triazol-1-yl)butan-1-one (KK15);
4-[2-(2,6-dimethylphenoxy)ethoxy]-1-phenyl-2-(1H-1,2,4-triazol-1-yl)butan-1-one (KK16);
4-[2-(3-trifluoromethylphenoxy)ethoxy]-1-phenyl-2-(1H-1,2,4-triazol-1-yl)butan-1-one (KK17);
4-[2-(2-fluorophenoxy)ethoxy]-1-phenyl-2-(1H-1,2,4-triazol-1-yl)butan-1-one (KK18);
4-[2-(4-phenoxyphenoxy)ethoxy]-1-phenyl-2-(1H-1,2,4-triazol-1-yl)butan-1-one (KK19);
4-[2-(4-phenylphenoxy)ethoxy]-1-phenyl-2-(1H-1,2,4-triazol-1-yl)butan-1-one (KK20);
6-(2-methylphenoxy)-1-phenyl-2-(1H-1,2,4-triazol-1-yl)hexan-1-one (KK101);
6-(2,6-dimethylphenoxy)-1-phenyl-2-(1H-1,2,4-triazol-1-yl)hexan-1-one (KK102);
6-(3,6-dimethylphenoxy)-1-phenyl-2-(1H-1,2,4-triazol-1-yl)hexan-1-one (KK103);
6-(4-nitrophenoxy)-1-phenyl-2-(1H-1,2,4-triazol-1-yl)hexan-1-one (KK106);
can be mentioned, but are not limited to these. Of these, KK3 and KK5 are more preferred, and KK5 is particularly preferred.

The compound represented by the general formula (I) or a salt thereof has the effect of inhibiting the biosynthesis of strigolactone in plants, and can be applied to plants, for example, for the purpose of increasing plant branching. In addition, the compound represented by the general formula (I) or a salt thereof can promote tillering in gramineous plants. As used herein, the term "tiller" means that side shoots develop and grow from joints of stems near the root in gramineous crops. should be interpreted in the broadest sense. Therefore, by applying the inhibitor of the present invention to rice and sugarcane, it is possible to achieve an increase in biomass through branching.

In addition, since the compound represented by the general formula (I) or a salt thereof can increase the number of flowers in flowering plants by increasing branching, it can be applied as an agent for increasing the number of flowers in agricultural and horticultural applications. is. The flowering plants to be applied are not particularly limited, and the present invention can be applied to any flowering plants such as agricultural crops such as rice and fruit trees, and garden plants such as tulips and roses.

Furthermore, strigolactones promote seed germination of root-parasitic plants Striga and Orobanche and increase parasitic weed parasitism on crops. By inhibiting the biosynthesis of strigolactone, it is possible to prevent the germination of parasitic weeds, preferably parasitic weeds such as Striga and Orobanche, and to suppress the parasitism of parasitic plants on crops, thereby increasing crop yields.

The inhibitor of the present invention can be prepared, for example, as an agrochemical composition using formulation additives well known in the art. The form of the agrochemical composition is not particularly limited, and any form may be adopted as long as it is available in the art. For example, compositions in the form of emulsions, liquids, oils, water solutions, wettable powders, flowables, powders, fine granules, granules, aerosols, fumigants, or pastes can be used. The method for producing the agrochemical composition is also not particularly limited, and methods available to those skilled in the art can be appropriately employed. As the active ingredient of the inhibitor of the present invention, two or more compounds represented by the above formula (I) or salts thereof may be used in combination. In addition, depending on the purpose of application, active ingredients of other agricultural chemicals such as insecticides, fungicides, fungicides and herbicides may be blended. The application method and application amount of the inhibitor of the present invention can be appropriately selected by those skilled in the art according to conditions such as application purpose, dosage form, and application site. For rice, for example, about 0.1 μM to 50 μM, preferably about 0.5 to 20 μM can be selected, but the application amount is not limited to the above specific range.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the scope of the present invention is not limited to the following examples.

1. Production of strigolactone biosynthesis inhibitor
1-Phenyl-2-(1H-1,2,4-triazol-1-yl)ethanone (1.08 g) was dissolved in dimethylformamide (14 mL) and sodium hydride (0.85 g) was added under nitrogen and ice. Added cold. 2-(2-bromoethoxy)ethoxy)benzene was dissolved in dimethylformamide (5 mL) and added. After reacting at room temperature for 30 minutes, reacting at 75° C. for 2 hours, returning to room temperature again, and reacting for 2.5 hours. After adding water on ice to stop the reaction, the mixture was extracted three times with ethyl acetate, dried over anhydrous sodium sulfate and concentrated under reduced pressure. The concentrate was separated by silica gel column chromatography (hexane:ethyl acetate = 3:1, changing the ethyl acetate concentration step by step to 1:1) to obtain 4-(2-phenoxyethoxy)-1-phenyl 111 mg (5.5%) of white crystals of -2-(1H-1,2,4-triazol-1-yl)butan-1-one were obtained.
¹ H NMR (400 MHZ CDCl3): d = 8.31 (s, 1H), 7.94 (d, J = 7.5 HZ, 2H), 7.91 (s, 1H), 7.56 (t , J = 7.3, 1H), 7.41 (t, J = 7.7 HZ, 2H), 7.29 (t, J = 7.9 HZ, 2H), 7.00-6.89 ( m, 3H), 6.31 (dd, J = 9.9, 5.2 HZ, 1H), 4.11 (t, J = 4.6 HZ, 2H), 3.81-3.68 (m , 2H), 3.68-3.59 (m, 1H), 3.33-3.24 (m, 1H), 2.62-2.50 (m, 1H), 2.41-2.30 (m, 1H). ^13C NMR (400 MHz CDCl3): d 194.1, 159.2, 151.8, 143.7, 134.2 134.3, 134.2, 129.6, 129.1, 128.8, 121 .2, 114.7, 69.9, 67.2, 66.4, 60.4, 32.7

Similarly, the compounds in Table 1 below were prepared.

2. Strigolactone inhibitory action
(A) Method
(i) Method for growing rice Sterilized solution I (2.5% sodium hypochlorite, 0.01% Tween-20) was added to rice seeds (Shiokari) and shaken at room temperature for 15 minutes. Sterilized solution I was discarded, sterilized solution II (2.5% sodium hypochlorite) was added, and the mixture was shaken at room temperature for 15 minutes. The sterilized solution II was discarded in a clean bench, the seeds were washed with sterilized water five times, and allowed to stand at 25°C in the dark for 2 days. Two days later, the germinated seeds were transplanted to a rice hydroponic agar medium and allowed to stand at 25°C for 6 days with a light period of 16 hours and a dark period of 8 hours. 12 mL of a rice hydroponic medium was added to a 12-mL brown vial, and rice plants were transplanted from the agar medium and allowed to stand at 25° C. for 6 days with a light period of 16 hours and a dark period of 8 hours. On the way, on the 4th day, 5 mL of the rice hydroponic medium was supplemented. The rice hydroponic medium was replaced with a compound-containing hydroponic medium, and allowed to stand at 25°C for 24 hours. The hydroponic solution was collected as it was, and the roots were stored at 4°C in a state of being immersed in acetone after measuring the weight.

(ii) Purification of rice hydroponic solution After adding 200 pg of d6-4-deoxyorobanchol per 10 mL of rice hydroponic solution, extraction was performed twice with 3 mL of ethyl acetate. The organic layer was dried with nitrogen gas, added to Sep-pak Silica 1mL cartridges (Waters), washed with ethyl acetate:n-hexane (15:85), and then ethyl acetate:n-hexane (35:65). eluted with Samples were evaporated to dryness, dissolved in 50% acetonitrile, and analyzed by LC/MS-MS.

(iii) Purification of rice roots 200 pg of d6-4-deoxyorobanchol was added to the acetone-soaked roots and then crushed. After the solid matter was filtered and dried with nitrogen gas, ethyl acetate and water were added, and extraction was performed twice with ethyl acetate. The organic layer was dried, dissolved in 10% acetone, added to Oasis HLB 3 mL cartridges (Waters), washed with deionized water, and eluted with acetone. The organic layer was dried with nitrogen gas, added to Sep-pak Silica 1mL cartridges (Waters), washed with ethyl acetate:n-hexane (15:85), and then ethyl acetate:n-hexane (35:65). eluted with Samples were evaporated to dryness, dissolved in 50% acetonitrile, and analyzed by LC/MS-MS.

(B) Results FIGS. 1 to 3 show the strigolactone secretion inhibitory effect of treatment with the test compound in rice. FIG. 4 shows the inhibitory effect of endogenous strigolactone levels. 4DO in the figure indicates 4-deoxyorobanchol.

3. Expression of strigolactone biosynthetic genes
(A) Method Arabidopsis thaliana seeds were surface-sterilized with 70% ethanol and then sown on 1/2 MS medium. After being allowed to stand at 4°C for 2 days, it was grown at 22°C for 4 weeks. Ten individuals each were immersed in a solution in which KK5 was added to sterilized water so as to be 5 μM, and allowed to stand for one day. RNA was extracted from the roots of the treated plants using Plant RNA Isolation reagent (Invitrogen) according to the attached protocol. 1 μg of RNA was reverse transcribed using PrimeScript RT reagent Kit with gDNA Eraser (TaKaRa). Thermal Cycler Dice Real Time System II (TaKaRa) was used to quantify the expression level. Table 2 shows the sequences of the gene primers used. Quantitative values were calculated using the attached software.

(B) Results FIG. 5 shows the effect of strigolactone biosynthetic gene expression in Arabidopsis thaliana. The expression levels of AtMAX3 and AtMAX4, genes for strigolactone biosynthesis, were significantly increased compared to the untreated group. Inhibition of strigolactone biosynthesis is known to increase expression levels of strigolactone biosynthesis genes due to a feedback effect, and KK5 was shown to inhibit strigolactone biosynthesis in Arabidopsis thaliana. .

4. Arabidopsis branching test
(A) Method After sterilizing the surface of Arabidopsis seeds with 70% ethanol, 1 seed was seeded in PCR tubes containing 200 μL of 1/2 MS medium. After standing at 4°C for 2 days, it was grown at 22°C for 1 week. After that, the lower portion (about 5 mm) of the PCR tube was cut off using a heated SURGICAL BLADE (Kai Industries Co., Ltd.) in a clean bench. 16 PCR tubes were arranged at regular intervals on one 96-well PCR tube stand. It was grown for 4 weeks in a hydroponic medium in which KK5 was adjusted to 0.1 μM, 1 μM and 3 μM (n=4) in a PCR tube. The hydroponic solution was added once every three days and replaced once a week. The number of branches elongated by 2 mm or more was counted.

(B) Results Figure 6 shows the number of branches when KK5 was added. 3 μM KK5 treatment significantly increased the number of branches. This suggests that KK5 has a branching-promoting effect.

5. Arabidopsis germination test
(A) Method Arabidopsis thaliana seeds were surface-sterilized with 70% ethanol, seeded in 1/2 MS medium containing each compound, and allowed to stand at 4° C. for 2 days. The germination rate was measured after standing overnight at 22°C.

(B) Results The germination rate results are shown in FIG. Treatment with paclobutrazol, a gibberellin biosynthesis inhibitor, significantly reduced the germination rate. With TIS108 treatment, a decrease in germination rate was observed as the treatment concentration was increased to 3 μM and 10 μM, but no decrease in germination rate was observed with KK5 treatment. This suggests that KK5 is a compound with weaker gibberellin biosynthesis inhibitory activity and fewer side effects than TIS108.

6. Arabidopsis thaliana hypocotyl elongation test in the dark
(A) Method
20 ml of 1/2 MS medium was dispensed into each plant box. TIS108 and KK5 were added to 1 µM each. 5 boxes each were prepared. Sterilized seeds were inoculated into each medium. After standing at 4°C for 2 days, it was grown at 22°C for 1 week while being wrapped in aluminum foil. Hypocotyl length was measured.

(B) Results FIG. 8 shows the hypocotyl length. Treatment with brassinazole, an inhibitor of brassinosteroid biosynthesis, significantly inhibited hypocotyl elongation. On the other hand, no suppression was observed with TIS108 or KK5 treatment. From this, it was clarified that TIS108 and KK5 have weak or no inhibitory activity on brassinosteroid biosynthesis.

7. Rice second leaf sheath elongation test
(A) Method Sterile solution I (2.5% sodium hypochlorite, 0.01% Tween-20) was added to rice seeds (shiokali) and shaken at room temperature for 15 minutes. Sterilized solution I was discarded, sterilized solution II (2.5% sodium hypochlorite) was added, and the mixture was shaken at room temperature for 15 minutes. The sterilized solution II was discarded in a clean bench, the seeds were washed with sterilized water five times, and allowed to stand at 25°C in the dark for 2 days. Two days later, the germinated seeds were transplanted to a rice hydroponic agar medium containing a compound at a concentration of 50 μM, and the length of the second leaf sheath after standing at 25°C for 6 days with a light period of 16 hours and a dark period of 8 hours. was measured.

(B) Results Figure 9 shows the length of the second leaf sheath. Treatment with paclobutrazol, a gibberellin biosynthesis inhibitor, significantly inhibited elongation of the second leaf sheath. On the other hand, no suppression was observed with TIS108, KK5, KK12, KK13, KK16 and KK18 treatments. From this, it was clarified that these compounds have no gibberellin biosynthesis inhibitory activity in rice.

Claims (11)

General formula (I) below:
(Wherein, R ¹ represents a hydrogen atom, an alkyl group, a halogenated alkyl group, an alkoxy group, a carboxyl group, an aryl group, an aryloxy group, a hydroxyl group, an amino group, a nitro group, or a halogen atom; R ² and R ³ represents a combination of a hydroxyl group and a hydrogen atom, or ^R2 and ^R3 together represent an oxo group; _L1 is ( _CH2 ) _2- O-( _CH2 ) ₂ -O or _CH2- CH═CH—CH ₂ —O; R ⁴ is a hydrogen atom, an alkyl group, a halogenated alkyl group, an alkoxy group, a carboxyl group, an aryl group, an aryloxy group, a hydroxyl group, an amino group, a nitro group, or a halogen atom When R ¹ and R ⁴ are substituents other than hydrogen atoms, the number of substituents is 1 to 2. A strigolactone biosynthesis inhibitor comprising a compound represented by ) or a salt thereof . 2. The strigolactone biosynthesis inhibitor according to claim ¹ , wherein R1 is a hydrogen atom. 3. The strigolactone biosynthesis inhibitor according to claim 1 or 2, wherein ^R2 and ^R3 together are an oxo group. An agent for increasing plant branching, comprising the strigolactone biosynthesis inhibitor according to any one of claims 1 to 3. A tillering promoter for gramineous plants comprising the strigolactone biosynthesis inhibitor according to any one of claims 1 to 3. An agent for increasing the number of flowers, comprising the strigolactone biosynthesis inhibitor according to any one of claims 1 to 3. A biomass increasing agent comprising the strigolactone biosynthesis inhibitor according to any one of claims 1 to 3. A crop yield increasing agent comprising the strigolactone biosynthesis inhibitor according to any one of claims 1 to 3. A parasitic weed germination inhibitor comprising the strigolactone biosynthesis inhibitor according to any one of claims 1 to 3. General formula (I) according to claim 1 (wherein R ¹ is a hydrogen atom, an alkyl group, a halogenated alkyl group, an alkoxy group, a carboxyl group, an aryl group, an aryloxy group, a hydroxyl group, an amino group, a nitro group, or represents a halogen atom; R ² and R ³ represent a combination of a hydroxyl group and a hydrogen atom, or R ² and R ³ together represent an oxo group; L ₁ represents (CH ₂ ) ₂ -O- ( _CH2 ) ₂ -O or _CH2 -CH=CH- _CH2 -O; ^R4 is a hydrogen atom, an alkyl group, a halogenated alkyl group, an alkoxy group, a carboxyl group, an aryl group, an aryloxy group, represents a hydroxyl group, an amino group, a nitro group, or a halogen atom.When R ¹ and R ⁴ are substituents other than hydrogen atoms , the number of substituents is 1 to 2. A compound represented by ) or its salt. 6-(2-methylphenoxy)-1-phenyl-2-(1H-1,2,4-triazol-1-yl)hexan-1-one (KK101);
6-(2,6-dimethylphenoxy)-1-phenyl-2-(1H-1,2,4-triazol-1-yl)hexan-1-one (KK102);
6-(3,6-dimethylphenoxy)-1-phenyl-2-(1H-1,2,4-triazol-1-yl)hexan-1-one (KK103);
6-(4-nitrophenoxy)-1-phenyl-2-(1H-1,2,4-triazol-1-yl)hexan-1-one (KK106);
A compound or a salt thereof, which is at least one selected from the group consisting of