PRACTICAL METHOD FOR DETERMINING A CHEMICAL HYBRIDIZING AGEN -APPLICATION TIME

Technical Field

The present invention relates to a practical method for determining a chemical hybridizing agent- application time for the stable production of excellent wheat F- _j _ hybrid seeds.

Background Art

JP-A-62-77302 discloses a method of male- sterilizing plants by treating plants with a certain kind of triazine derivative. In order to stably produce excellent F* _j _ hybrid seeds which mean first filial seeds obtained by cross- pollinating seed parent plants with the pollen of pollen parent plants, the following requirements should be met:

(1) The seed parent plants should have an ex- tremely high male sterility.

(2) The female fertility of the seed parent plants should not be reduced.

(3) The seed setting ratio of the seed parent plants should not be damaged. (4) The quality of F-*_ hybrid seeds should not be damaged.

For example, in a method comprising inducing

the male sterility by treating plants with a certain kind of compound and disturbing the production of pollen or causing the pollen to lose its function _r it is de¬ sired to find a practically optimum combination of various factors by considering such factors as selection of the compound, target plant, chemical hybridizing agent-application method, chemical hybridizing agent- application time and the like so as to meet the above requirements. Particularly at present, the application time is only roughly determined from an expected heading day, and no method of exactly and practically determining the chemical hybridizing agent-application time has been known. In the practical field for producing wheat F-^ hybrid seeds, the growth rate of various plant varieties changes depending on the natural conditions such as atmospheric temperature, rainfall and/or sunshine hours, and the like. Therefore, it has frequently occurred to miss the right time to apply chemical hybridizing agents and to fail to exhibit a sufficient effect of the chemical hybridizing agent.

Disclosure of Invention

In view of the situation mentioned above, the present inventors have made an extensive study, and as a result have found that stable production of excellent wheat F* hybrid seeds becomes possible by foliar- applying a chemical hybridizing agent containing as an

active ingredient 2-hydroxymethyl-l,2,4-triazin-3,5- dione or its metal salt onto a certain kind of wheat variety at an application time determined by conditions based on two parameters of average young spike length of the main stem and index number of flag leaf development. The present inventors thus completed the present invention.

An object of the present invention is to allow seed parent plants of winter habit wheat variety to produce wheat F-^ hybrid seeds by foliar-applying a chemical hybridizing agent containing as an active ingredient 2-hydroxymethyl-l,2,4-triazin-3,5-dione or its metal salt onto the seed parent plants and then cross-pollinating the seed parent plants with the pollen of pollen parent plants of wheat variety.

According to the present invention, there are provided a method for determining the time for applying a chemical hybridizing agent containing as an active ingredient 2-hydroxymethyl-l,2,4-triazin-3,5-dione or its metal salt to plants of winter habit wheat variety in order to make the plants stably produce wheat F^ hybrid seeds when the chemical hybridizing agent is foliar-applied to seed parent plants of winter habit wheat variety and then the chemical hybridizing agent- applied seed parent plants are cross-pollinated with the pollen of pollen parent plants of wheat variety, which method comprises the step of: determining the average young spike length of

the main stem and the index number of flag leaf development of the plants of winter habit wheat variety, while confirming that the following three conditions are satisfied: (a) the average young spike length of the main stem is between 30 mm and 60 mm, both inclusive,

(b) the index number of flag leaf development is between 6.5 and 11, both inclusive, and

(c) the index number of flag leaf development ≥ 0.2 x the average young spike length of the main stem

(mm) - 1.5; and a method for producing wheat F^_ hybrid seeds which comprises the steps of: determining the average young spike length of the main stem and the index number of flag leaf develop- ment of plants of winter habit wheat variety, while confirming that the following three conditions are satisfied:

(a) the average young spike length of the main stem is between 30 mm and 60 mm, both inclusive, (b) the index number of flag, leaf development is between 6.5 and 11, both inclusive, and

(c) the index number of flag leaf development

≥ 0.2 x the average young spike length of the main stem

(mm) - 1.5, foliar-applying a chemical hybridizing agent containing as an active ingredient 2-hydroxymethyl- l,2,4-triazin-3,5-dione or its metal salt onto seed parent plants of winter habit wheat variety at a time

determined in the preceding step, cross-pollinating the chemical hybridizing agent-applied seed parent plants with the pollen of pollen parent plants of wheat variety, and harvesting the seeds produced by the seed parent plants.

Best Mode for Carrying out the Invention

The seed parent plants which are the target of the present invention are of winter habit wheat variety of wheat varieties. The winter habit wheat variety refers to a variety which requires a low temperature to shift from vegetative growth to reproductive growth, belonging to the variety group generally called "winter habit wheat" or "winter wheat" . This variety group belongs genetically to a wheat variety group which carry recessive alleles at all five loci of genes for response to vernalization, yrn 1, yrn 2 , yrn 3, yrn 4 and yrn 5. The plants of this variety group can be briefly distinguished from the other plants by determining whether or not they are reached to heading when cultivated in a phytotron (an air conditioning room) kept at 20°C and under 24 hours day length condition. The plants of this variety group do not come to heading even if cultivated for 90 days or more under such conditions.

For example, there are given wheat varieties such as Triumph 64, Centura, Colt, Vona, Cree, Chisholm,

Norwin, Siouxland, Newton, Rose, Winridge, Neeley, Ute, Arkan, Hawk, Phoenix, Arthur 71, Coker 797, Rosette, Hart, Titan, Rosen, Wheeler, Adder, Roland, Vel, Adena, Fillmore, Mission, Parade, Stetson, Aquila, Ambassador, Talent, Fidel, Galahad, Armada, ador, Boxer, Norman,

Hamlet, Voyage, Kay, Agassiz, Saluda, Brule, Frankenmuth, Bezostaja 1, Avalon, Kitakami Komugi and the like.

There is no limitation to the pollen parent plants, so far as they belong to wheat variety. . Prefer- ably, however, there can be given a variety which has a large anther, yields pollen in large amounts and puts the anther out of the glume at the anthesis time to increase the amount of scattering pollen. Also, a variety which is easy in synchronizing its anthesis time with that of the seed parent plant, is suitable.

2-Hydroxymethyl-l,2, -triazin-3,5-dione, which is the active ingredient of the chemical hybridizing agent suited for effecting the present invention, can be synthesized by the method of M. Prytas, et al. [Collection Czechslov Chem. Commun., 30, 81 (1965)]. Due to the chemically acidic property, 2- hydroxymethyl-l,2,4-triazin-3,5-dione is easily converted to the various metal salts. Of these metal salts, those which are particularly useful are alkali metal salts (e.g. sodium salt, potassium salt, lithium salt) and alkaline earth metal salts (e.g. calcium salt, barium salt, strontium salt) .

Chemical hybridizing agents containing as an

active ingredient the above compound or its metal salt are obtained by mixing the compound or its metal salt with, usually, additives (e.g. surface active agents, auxiliaries for formulation) and/or a carrier (e.g. solid carriers, liquid carriers) , and then formulating the resulting mixture into various forms such as aqueous formulations, water-soluble formulations, wettable powders, granular wettable powders, dusts and the like. These chemical hybridizing agents usually contain the above active ingredient in an amount of 0.1 to 90%, preferably 1 to 70% by weight.

The surface active agents include anionic surface active agents such as alkyl sulfates, alkylaryl sulfonates, dialkyl sulfosuccinates, polyoxyethylene alkylaryl ether phosphates and the like, and nonionic surface active agents such as polyoxyethylene alkyl- ethers, polyoxyethylene .alkylaryl ethers, polyoxy¬ ethylene polyoxypropylene block copolymers, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters and the like. The auxiliaries for formulation include lignin sulfonates, sodium alginates, polyvinyl alcohol, gum arabic, CMC (carboxymethyl cellulose) , PAP (isopropyl acid phosphate) and the like.

The solid carriers include fine powders or granules of kaolin clay, attapulgite clay, bentonite, terra alba, pyrophyllite, talc, diatomaceous earth, calcite, walnut shell powder, urea, ammonium sulfate, synthetic hydrated silicon dioxide and the like. The

liquid carriers include aromatic hydrocarbons (e.g. xylene, methylnaphthalene), alcohols (e.g. isopropanol, ethylene glycol, methyl cellosolve, ethyl cellosolve), ketones (e.g. acetone, cyclohexanone, isophorone), vegetable oils (e.g. soybean oil, cotton seed oil), dimethyl sulfoxide, acetonitrile, water and the like. For applying the above chemical hybridizing agents, foliar application is used. The dosage rate of the active ingredient varies with preparation forms and the like. Usually, however, it is about 1 to about 8 kg/ha.

When the aqueous formulations, water-soluble formulations, wettable powders, granular wettable powders and the like are applied, it is usual before application to dilute a prescribed amount of these chemical hybridizing agent with water of about 0.5 to about 20 liters/are to obtain an aqueous dilute solution, with optional addition of auxiliaries (e.g. spreading agents) . ^' As the spreading agent, there are given, in addition to the foregoing surface active agents, polyoxyethylene resin solutions (ester), lignin sulfo¬ nates, abietates, dinaphthylmethanedisulfonates, paraffin and the like. Further, the chemical hybridizing agents can be used in mixture with plant growth regulators, herbicides, insecticides, acaricides, fungicides and the like.

Next, a method for determining the application time will be illustrated.

The parameters used in the present method are defined as follows. The young spike length refers to the length (mm) of a young spike formed in a stem. The average young spike length of a main stem refers to a mean value obtained by measuring the length of a young spike formed in the apparently thickest and longest stem among plants, and averaging the resulting measurement values. The number of samples needs to be a number required for the distribution of measurement values to follow the normal distribution. For example, it is usually 20 or more, preferably from about 30 to about 50. The index number of flag leaf development is defined as follows.

A growth stage at which the tip of a flag leaf has just emerged from the leaf sheath is taken as 0. A growth stage at which the flag leaf has completely developed outside is taken as 10. Further, a growth stage at which the leaf sheath of the flag leaf has completely emerged outside is taken as 20. The propor¬ tion of the portion of the flag leaf developed out of the leaf sheath to the total of the above portion and the portion of the flag leaf remaining undeveloped inside the leaf sheath is classified into ten stages (index numbers between 0 and 10). The proportion of the portion of leaf sheath from which the flag leaf has been

exposed outside to the total of the above portion and the portion of the leaf sheath in which the flag leaf remains unexposed is classified into ten stages (index numbers between 10 and 20). On the basis of these parameters, the application time can be exactly and practically confirmed when the following three conditions are satisfied:

(a) The average young spike length (mm) of the main stem should be from 30 to 60, both inclusive.

(b) The.index number of flag leaf development should be from 6.5 to 11, both inclusive.

(c) The index number of flag leaf development ≥ 0.2 x the average young spike length of the main stem (mm) - 1.5.

A method for producing wheat F*-_ hybrid seeds will be explained.

A commonly used method for producing wheat F*^ hybrid seeds comprises, for example: (1) alternately planting seed parent plants and pollen parent plants which are to be crossed with each other (In this case, the number of rows and widt between rows for every plant vary with the variety of the plan , environmental conditions and the like) , (2) foliar-applying a chemical hybridizing agent onto the seed parent plants at an appropriate application time, and (3) cross-pollinating the chemical hybridizing

agent-applied seed parent plants with the pollen of the pollen parent plants to allow them to stably produce excellent wheat F*-_ hybrid seeds.

By adopting the method for determining the application time of a chemical hybridizing agent of the present invention to the second step, the desired seeds can be harvested more efficiently than before.

Next, the method of the present invention will be illustrated in more detail with reference to the following formulation examples, general examples and test examples.

First, formulation examples will be shown. In the examples, all parts are by weight.

Formulation Example 1 Aqueous formulation Dissolving 1 part of sodium or potassium salt of 2-hydroxymethyl-l,2,4-triazin-3,5-dione in 99 parts of water gives an aqueous formulation.

Formulation Example 2 Water-soluble formulation

Five parts of sodium or potassium salt of 2- hydroxymethyl-l,2,4-triazin-3,5-dione and 95 parts of sodium sulfate are well pulverized and mixed. The resulting mixture is granulated with water and dried to obtain a water-soluble formulation.

Formulation Example 3 Wettable powder Thoroughly pulverizing and mixing 10 parts of

sodium or potassium salt of 2-hydroxymethyl-l,2,4- triazin-3,5-dione, 3 parts of calcium lignosulfonate, 2 parts of sodium lauryl sulfate and 85 parts of synthetic hydrated silicon dioxide give a wettable powder.

Formulation Example 4 Granular wettable powder

Five parts of 2-hydroxymethyl-l,2,4-triazin- 3,5-dione or its sodium or potassium salt, 10 parts of sodium polycarbonate, 2 parts of sodium dodecylbenzene- sulfonate and 83 parts of kaolin clay are well pulver- ized and mixed. The resulting mixture is granulated with water and dried to obtain a granular wettable powder.

Formulation Example 5 Dust

Thoroughly pulverizing and mixing 1 part of 2-hydroxymethyl-l,2,4-triazin-3,5-dione or its sodium or potassium salt, 0.5 part of synthetic hydrated silicon dioxide and 98.5 parts of kaolin clay give a dust.

Next, using a general example, comparison of the present method with the conventional method will be made on the production of wheat F* _j _ hybrid seeds.

In the field, seed parent plants of winter habit wheat variety and pollen parent plants of wheat variety, which plants are to be crossed with each other, are sowed at a ratio of 2 g-seed weight per meter. The seed parent plants are sowed in two rows and the pollen parent plants are sowed in one row between the rows of

seed parent plants. The seed parent plants and the pollen parent plants are sowed repeating the sowing order of pollen parent plants, seed parent plants and seed parent plants. The distance between the rows is 30 cm. One plot is made 3 meters in length.

After growth, an aqueous dilute solution prepared by diluting a chemical hybridizing agent containing as an active ingredient 2-hydroxymethyl- l,2,4-triazin-3,5-dione or its metal salt with water containing 5 g/liter of a spreading agent, is foliar- applied onto the seed parent plants in an amount of 10 liters/are corresponding to 4 kg/ha as the dosage rate of the active ingredient at a prescribed application time. The application time is determined by either the presently claimed method on the basis of two parameters of the average young spike length of the main stem and the index number of flag leaf development or the conventional method on the basis of an expected heading day. The seed parent plants are allowed to produce wheat F-*_ hybrid seeds by cross-pollinating them with the pollen of the pollen parent plants.

As a result, according to the presently claimed method, the seed parent plants have a high male sterility and show no reduction in the female fertility because the presently claimed method can determine the application time exactly and practically. Also, according to the presently claimed method, there is no

damage in the seed setting ratio and quality and germinability of the produced F- _] _ hybrid seeds. Thus, the presently claimed method can stably produce excellent wheat F* _j _ hybrid seeds. In contrast, the conventional method frequ¬ ently misses the right chemical hybridizing agent- application time because the growth rate of plants of various varieties changes depending on the natural conditions such as atmospheric temperature, rainfall and/or sunshine hours, and the like. Thus, the effect of the chemical hybridizing agent cannot sufficiently be displayed, which makes it difficult to stably produce excellent wheat F*-_ hybrid seeds.

Test examples will be shown.

Test Example 1 Field test

Various wheat varieties sowed at a ratio of 3 g-seed weight per meter were cultivated in the field in two rows. At a prescribed application time after their growth, an aqueous dilute solution prepared by diluting a chemical hybridizing agent containing as an active ingredient the potassium salt of 2-hydroxymethyl-l,2,4- triazin3,5-dione prepared according to Formulation Example 1 with water containing 5 g/liter of a spreading agent was foliar-applied to the grown plants in an amount of 10 liters/are.

After heading, every ear was prevented from cross-pollination by covering it with a bag. After

ripening, every ear covered with a bag was harvested and examined for the number of spikelets and the number of seeds. The effect of the chemical hybridizing agent was expressed by the value x. The value x is obtained as follows: The ratio of the number of seeds per spikelet of every ear covered with a bag (treated plot) to that of every ear not covered with a bag (untreated plot) is calculated and expressed in percentage, and then a difference between 100 and the numerical value in percentage is calculated. The value x refers to the thus calculated difference. A method for producing the wheat F**L hybrid seeds was evaluated according to the following standard based on the value x: Excellent: x > 95 Good: 95 ≥ x > 70

Bad: 70 ≥ x. In the above test, the length of the test plot was made 1.25 meters per plot.

The results are shown in Table 1.

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Table 1 (cont'd)

From the above results, it can be seen that in order to exactly and practically determine the applica¬ tion time, it is essential to satisfy the foregoing three conditions (a), (b) and (c) based on the two parameters of the average young spike length of the main stem and the index number of flag leaf development.

Test Example 2 Production test for F-^ -hybrid seeds

A wheat variety Saluda was used as the seed parent plant, and a wheat variety Park was used as the pollen parent plant. The seed parent plants and pollen parent plants were sowed at a ratio of 2 g-seed weight per meter in the field, the seed parent plants were sowed in two rows and the pollen parent plants were sowed in one row between the rows of the seed parent plants, the seed parent plants and pollen parent plants were sowed repeating the sowing order of pollen parent plants, seed parent plants and seed parent plants, the distance between the rows was 30 cm, and one plot was made 3 meters in length. At a time after growth wherein the average young spike length (mm) of the main stem of the seed parent plants was 40.4 and the index number of flag leaf development thereof was 10, an aqueous dilute solution prepared by diluting a chemical hybridizing agent containing as an active ingredient the potassium salt of 2-hydroxymethyl-l,2,4-triazin-3,5-dione prepared accord¬ ing to Formulation Example 1 with water containing 5 g/

liter of a spreading agent was foliar-applied onto the seed parent plants in an amount of 10 liters/are. After heading, a part of the ears was prevented from cross- pollination by covering it with a bag in the same manner as in Test Example 1. After ripening, every ear covered with a bag was harvested and examined for the number of spikelets and number of seeds, and the value x was calculated. On the other hand, the remainder of the ears was cross-pollinated with the pollen of the pollen parent plants by allowing the pollen to fly about under the natural conditions. After ripening, all the ears of the seed parent plants were gathered, and the produced seeds were examined for the appearance, purity, yield and ratio of germination. The results are shown in Table 2.

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Table 2

Notes:

(1) Evaluated in five stages, excellent, good, fair, bad and killed, by macroscopic observation.

(2) Ratio to the untreated plot.

As the value x shows, the seed parent plants have an extremely high male sterility at every dosage rate. Also, as the ratio of fertility of the open- pollinated plants shows, the female fertility of the seed parent plants shows no such reduction as would become a problem in practical use. Also, as the yield and purity of the produced F*-_ hybrid seeds show, the seed setting ratio of the F _] _ hybrid seeds shows no such reduction as would become a problem in practical use. Further, as the appearance, the 1000 kernel weight and the germination ratio of the- F* _j _ hybrid seeds show, there is no problem about the quality of the F-^ hybrid seeds.

Test Example 3 Production test for F-^ hybrid seeds

Using a wheat variety Brule as the seed parent plants and a wheat variety Avalon as the pollen parent plants, a production test for the F* _j _ hybrid seeds was carried out in the same manner as in Test Example 2. A chemical hybridizing agent used was one containing as an active ingredient the potassium salt of 2-hydroxymethyl- l,2,4-triazin-3,5-dione prepared according to Formula¬ tion Example 1. At a time when the average young spike length of the main stem of the seed parent plants was 50.5 mm and the index number of flag leaf development was 11, the above chemical hybridizing agent was foliar-applied onto the plants in a dosage rate of 8 kg/ha. As a result, the following results were obtained: The value x was 100, the ratio of fertility

of the open-pollinated plant was 42.5%, the appearance of the F*L hybrid seeds was good, the purity thereof was 100%, the 1000 kernel weight thereof was 105.6%, the yield thereof was 38.4%, and the ratio of germination thereof was 91.6%.

In the same manner as in Test Example 2, the seed parent plants have a complete male sterility as the value x shows. Also, as the ratio of fertility of the open-pollinated plants shows, the female fertility of the seed parent plants shows no such reduction as would become a problem in practical use. Also, as the yield and purity of the produced F*^ hybrid seeds show, the seed setting ratio of the F _] _ hybrid seeds shows no such damage as would become a problem in practical use. Further, as the appearance, the 1000 kernel weight and the germination ratio of the F-^ hybrid seeds show, there is no problem about the quality of the F* _j _ hybrid seeds.

Industrial Applicability

Foliar-applying a chemical hybridizing agent at the time determined in accordance with the invention enables the stable production of wheat F*-_ hybrid seeds.