JP2009051771A - NEW USE OF BACTERIUM BELONGING TO GENUS Azospirillum - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To impart various preferable characters to agriculturally useful plants by a biological means. <P>SOLUTION: This method for inhibiting insect damage, promoting the growth or increasing the yield of the plants by artificially infecting new endophyte bacteria belonging to the genus Azospirillum (e.g. bacterium of Accession Number NITE BP-194) to the plants belonging to Cruciferae, Gramineae, Leguminosae or Liliaceae is provided. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention is a method for artificially infecting a plant with an Azospirillum genus bacterium that is an endophyte to impart pest resistance to the plant, a method for promoting the growth of the plant, and a method for increasing the yield of the plant About.

  So far, pest control technology centered on chemical pesticides has contributed to efficient food security. However, in recent years, environmentally friendly agriculture with pesticide-free and reduced pesticides, including not only the efficiency of cultivation but also safe and secure areas, is desired, and pest control technology (for example, microbial pesticides) suitable for it is required. .

  The object of the present invention is to impart various favorable properties to agriculturally useful plants by biological means.

The present invention includes the following inventions.
(1) Insect resistance to cruciferous plants, including the step of artificially infecting cruciferous plants with bacteria that belong to the genus Azospirillum and have the ability to symbiotize in cruciferous plants and impart pest resistance to the plants A method of imparting sex.
(2) A plant belonging to the genus Azospirillum, including the step of artificially infecting a cruciferous plant with a bacterium that has the ability to symbiotically in the cruciferous plant and increase the yield of the plant leaf, How to increase yield.
(3) Insect resistance to gramineous plants, including the step of artificially infecting gramineous plants with bacteria that belong to the genus Azospirillum and have the ability to symbiotize in the gramineous plants and impart pest resistance to the plants A method of imparting sex.
(4) Promote the growth of gramineous plants, including the step of artificially infecting gramineous plants with bacteria that belong to the genus Azospirillum and have the ability to symbiotically grow in gramineous plants and promote the growth of the plants Method.
(5) Grain yield in Gramineae plants, including the step of artificially infecting Gramineae plants with bacteria belonging to the genus Azospirillum and having the ability to symbioticly in Gramineae plants and increase grain yield in the plants. How to increase.
(6) Promoting the growth of legumes, including the step of artificially infecting legumes with bacteria that belong to the genus Azospirillum and have the ability to symbiotically grow in the legumes and promote the growth of the plants Method.
(7) Grazing of legumes, including the step of artificially infecting legumes with bacteria that belong to the genus Azospirillum and have the ability to symbiotically grow in the legumes and increase the number of buds of the plants. How to increase the number.
(8) The number of root nodules in legumes including the step of artificially infecting legumes with bacteria belonging to the genus Azospirillum and having the ability to increase the number of root nodules in the leguminous plants How to increase.
(9) It belongs to the genus Azospirillum and includes a step of artificially infecting a lily family plant having a bulb with a bacterium that has the ability to symbioticly in the lily family plant having a bulb and increasing the yield of the bulb in the plant, A method for increasing the bulb yield in a lily family.
(10) The method according to any one of (1) to (9), wherein the bacterium is a novel genus Azospirillum (accession number NITE BP-194) or a mutant strain thereof.

  As used herein, “a novel bacterium belonging to the genus Azospirillum” refers to a bacterium belonging to the genus Azospirillum, which is disclosed in International Application PCT / JP2007 / 054624 and assigned accession number NITE BP-194.

  According to the present invention, by biological means, imparting pest resistance to cruciferous plants, imparting pest resistance to gramineous plants, promoting the growth of gramineous plants, grains in gramineous plants Increase yield, promote leguminous plant growth, increase legume planting, increase number of nodules in legumes, increase leaf yield of cruciferous plants Or it becomes possible to increase the yield of the bulb in a lily family plant.

1. Bacteria Bacteria that can be used in the present invention are bacteria belonging to the genus Azospirillum, the ability of symbiosis in the cruciferous plants to impart pest resistance to the plants, and the symbiosis in the gramineous plants. Ability to impart pest resistance to plants, Ability to symbiotically grow in grasses, Ability to symbiotic in grasses and increase grain yield in plants, Symbiosis in legumes The ability to promote the growth of the plant, the ability to grow symbiotically in the leguminous plant body, increase the number of buds of the plant, the ability to live in the legume plant body and increase the number of nodules in the plant, At least one selected from the group consisting of the ability to symbiotic in the plant and increase the yield of leaves of the plant, and the ability to symbiotic in the lily family having a bulb and increase the yield of bulbs in the plant Noh It is not particularly limited as long as it is a powerful bacterium. As a specific example, a novel bacterium belonging to the genus Azospirillum (Accession No. NITE BP-194) may be mentioned.

  A novel bacterium belonging to the genus Azospirillum (Accession No. NITE BP-194) is a novel bacterium isolated from rice by the present inventors and disclosed in International Application PCT / JP2007 / 054624. A new bacterium belonging to the genus Azospirillum has the substrate utilization ability shown in the following table.

A partial base sequence of 16S rDNA of a novel bacterium of the genus Azospirillum is shown in SEQ ID NO: 1 in the sequence listing.
Further, the bacterium that can be used in the present invention is a bacterium having the same ability as that of a novel genus Azospirillum (Accession No. NITE BP-194), for example, belonging to the genus Azospirillum and having the same carbon source as the above-mentioned novel genus Azospirillum. Examples include, but are not limited to, bacteria having assimilation ability and bacteria having 16S rDNA belonging to the genus Azospirillum and having at least a portion of the base sequence shown in SEQ ID NO: 1. Furthermore, it is a mutant strain produced by mutagenesis treatment of a novel bacterium belonging to the genus Azospirillum (Accession No. NITE BP-194), which has the ability to symbiotically grow in cruciferous plants and impart pest resistance to the plants, Ability to symbiotically grow in plants and impart pest resistance to plants, Ability to symbiotic in grasses and promote growth, Grain yields in grasses increase in plants Ability to symbioticly in the leguminous plant and promote the growth of the plant, ability to symbiotic in the leguminous plant and increase the number of arrivals of the plant, The ability to increase the number of nodules, the ability to symbiotic in the Brassicaceae plant and increase the yield of the leaves of the plant, and the ability to symbiotic to the Lilyaceae plant having a bulb and increase the yield of bulbs in the plant, Selected from the group consisting of Mutants having at least one capability is can also be suitably used for the present invention. Among these mutant strains, it belongs to the genus Azospirillum and has the same ability to assimilate the carbon source as described above, or a bacterium belonging to the genus Azospirillum, and at least a part of the base sequence shown in SEQ ID NO: 1. Bacteria having 16S rDNA contained in are preferred. The mutagenesis treatment can be performed using any suitable mutagen. Here, the term “mutagen” has a broad meaning and should be understood to include not only a drug having a mutagenic effect but also a treatment having a mutagenic effect such as UV irradiation. Examples of suitable mutagens include ethyl methanesulfonate, UV irradiation, N-methyl-N'-nitro-N-nitrosoguanidine, nucleotide base analogs such as bromouracil, and acridines, but any other effect A typical mutagen can also be used.

  The bacteria used in the present invention can be cultured under normal conditions by a normal culture method such as shaking culture. As a medium for culturing, sugars such as glucose, sucrose, starch and dextrin are used as a carbon source, ammonium salts such as ammonium sulfate, ammonium chloride and ammonium nitrate are used as nitrogen sources, inorganic nitrogen sources such as nitrates, yeast extract, corn Organic nitrogen sources such as steep leaker, meat extract, wheat germ, polypeptone, sugar cane squeezed (bacus), beer casks, soy flour, rice bran, fish meal, etc., and inorganic salts such as monopotassium phosphate, magnesium sulfate, manganese sulfate, sulfuric acid Examples thereof include synthetic or natural media containing salts containing phosphorus, potassium, manganese, magnesium, iron, etc., such as monoiron.

  In the method of the present invention, a bacterial culture solution can be used as it is, but a high bacterial concentration obtained by separating the bacterial culture solution by a method such as membrane separation, centrifugation, or filtration separation can also be used. .

  In the method of the present invention, a dried bacterial culture solution can also be used. Alternatively, a bacterial culture solution adsorbed on a porous adsorbent such as activated carbon powder, diatomaceous earth, or talc and dried can be used. The drying method may be a normal method, for example, freeze drying or vacuum drying. These dried products may be further pulverized by a pulverizing means such as a ball mill after drying.

  Bacteria can be used alone for the use of the present invention as the above-mentioned culture medium, high-concentration product or dried product, but in the same form as a normal microbial preparation (for example, powder, (Forms of wettable powders, emulsions, liquids, flowables, coatings, etc.) can also be used. Examples of optional components that can be used in combination include materials that can be applied to plants such as solid carriers and adjuvants.

2. Giving pest resistance to cruciferous plants, increasing leaf yield of cruciferous plants One form of the present invention belongs to the genus Azospirillum and symbiotics within cruciferous plants to impart pest resistance to the plants The present invention relates to a method for imparting insect resistance to a cruciferous plant, which comprises the step of artificially infecting the cruciferous plant with a bacterium having the ability to act.

  Another aspect of the present invention includes the step of artificially infecting a cruciferous plant with a bacterium belonging to the genus Azospirillum and having the ability to symbiotically grow in the cruciferous plant and increase the yield of the leaf of the plant, It relates to a method for increasing the yield of cruciferous leaves.

  In these forms, cruciferous plants include rape, turnip, chingensai, nozawana, mustard, Takana, Kobutana, mizuna, callaby, arugula, watercress, taasai, cauliflower, cabbage, kale, Chinese cabbage, komatsuna, Japanese radish, Japanese radish, broccoli, mecabbage , Horseradish, horseradish, and Arabidopsis thaliana.

  Examples of insect damage include feeding by a diamondback moth, a white butterfly, a white-tailed butterfly, a red-tailed moth, a cabbage moth, a red-tailed moth, a weevil, a leafhopper, a hornbill beetle, a hornbill beetle, a weevil, aphids, and a thrips.

  Examples of the method of applying the bacterium or the composition containing the same to these cruciferous plants in these embodiments include a seed coat, a method of irrigating, applying, or spraying a young plant. In particular, a method of artificially scratching seeds or plants and spraying and applying the bacterial solution is preferable. As other application conditions, it is desirable to apply before sowing in the field, such as at the time of sowing and seedling raising. Moreover, high expression of the effect can be expected by spraying the plants during field cultivation.

3. Giving pest resistance to grasses, promoting growth, increasing grain yield One form of the present invention belongs to the genus Azospirillum and is the ability to symbioticly coexist in grasses and impart pest resistance to the plants. The present invention relates to a method for imparting pest resistance to gramineous plants, including the step of artificially infecting gramineous plants with bacteria having

  Another aspect of the present invention includes a step of artificially infecting a gramineous plant with a bacterium belonging to the genus Azospirillum and having the ability to coexist in the gramineous plant body and promote the growth of the plant. The present invention relates to a method for promoting plant growth.

  Another aspect of the present invention includes a step of artificially infecting a gramineous plant with a bacterium belonging to the genus Azospirillum and having the ability to symbiotically grow in the gramineous plant and increase the grain yield in the plant. The present invention relates to a method for increasing grain yield in a family plant.

  Grains such as rice, wheat, barley, rye, triticale, pearl barley, sorghum, oats, corn, sugar cane, millet, millet, etc. can be mentioned as the gramineous plant in these forms. The grasses further include feed or grass such as buckwheat, buffalo grass, Bermuda grass, weeping grass, centipede grass, carpet grass, dalice grass, Kikuyu grass, and St. Augustine grass. Most preferred is rice.

  Insect damages in grasses include Drosophila, Nikaameiga, Ichimongiseseri, Knotomoiga, Ineyotou, Awayoto, Sujiriyotou, Futobiboyaga, Inebobiso hamushi, other potato beetles, rice flies, rice leaf moths, rice leaf moths, Other nematodes, rice weevil, click beetles, scarab beetles, grasshoppers, scallop apples, white-winged beetles, gangambo, scallops, feeding on white planthoppers, leafhoppers, leafhoppers, other planthoppers, leafhoppers, leafworms, beetles And soup by stink bugs.

  Examples of the method for applying the bacterium or the composition containing the same to the grass family in this embodiment include a seed coat, a method of irrigating, applying, or spraying the seedling. In particular, a method of artificially scratching seeds or plants and spraying and applying the bacterial solution is preferable. As other application conditions, it is desirable to apply before sowing in the field, such as at the time of sowing and seedling raising. Moreover, high expression of the effect can be expected by spraying the plants during field cultivation.

4. Growth promotion of leguminous plants, increase in the number of arrivals, increase in the number of nodules One form of the present invention is a bacterium belonging to the genus Azospirillum and having the ability to promote symbiosis within the legumes. The present invention relates to a method for promoting the growth of legumes, which comprises the step of artificially infecting legumes.

  Another aspect of the present invention includes the step of artificially infecting leguminous plants with bacteria belonging to the genus Azospirillum and having the ability to symbiotically grow in the legumes and increase the number of plants settled. The present invention relates to a method for increasing the number of arrivals of legumes.

  Another aspect of the present invention includes the step of artificially infecting legumes with a bacterium belonging to the genus Azospirillum and having the ability to symbiotically grow in the legumes and increase the number of nodules in the plants. The present invention relates to a method for increasing the number of nodules in a family plant.

  In these forms, examples of legumes include soybean, azuki bean, groundnut, kidney bean, pea, hana bean, broad bean, cowpea, chickpea, mung bean, lentil, lentil, and banbara bean. Most preferred is soybean.

  Examples of the method for applying the bacterium or the composition containing the same to the leguminous plant in this embodiment include a seed coat, a method of irrigating, applying, or spraying the seedling. In particular, a method of artificially scratching seeds or plants and spraying and applying the bacterial solution is preferable. As other application conditions, it is desirable to apply before sowing in the field, such as at the time of sowing and seedling raising. Moreover, high expression of the effect can be expected by spraying the plants during field cultivation.

5. Increasing the yield of bulbs in lily family One form of the present invention is a bacterium belonging to the genus Azospirillum, which is symbiotic in the lily family with bulbs and has the ability to increase the yield of bulbs in the bulb. It relates to a method for increasing the yield of bulbs in a lily family plant, comprising the step of artificially infecting a lily family plant having

  In this form, the lily family plants having bulbs include onion, rakkyo, garlic, leek, chives and lily. Most preferred is onion.

  Examples of the method of applying the bacterium or the composition containing the bacterium in this embodiment to a lily family include a seed coat, a method of irrigating, applying, or spraying a young plant. In particular, a method of artificially scratching seeds or plants and spraying and applying the bacterial solution is preferable. As other application conditions, it is desirable to apply before sowing in the field, such as at the time of sowing and seedling raising. Moreover, high expression of the effect can be expected by spraying the plants during field cultivation.

Golden moth feeding test
1． To elucidate the mechanism of insect resistance induction induced by the target endophyte, the resistance of Azospirillum sp. NITE BP-194 is clarified using Arabidopsis, a model plant of disease resistance.

2． Method <br/> Test strain: NITE BP-194
Inoculation concentration: 5 × 10 ⁶ cell / seed (converted to 1 × 10 ⁸ cell / ml) Control group: Non-inoculated plant: Arabidopsis Col-0
Target pests: Golden moth feeding time: 4 hours Number of samples processed: 15 samples in each treatment area

3． Experimental Method Arabidopsis seeds were sterilized by treatment with 70% ethanol for 20 seconds and 1% aqueous hypochlorous acid for 5 minutes, and then washed three times with sterilized distilled water for 20 minutes. About 20 seeds of sterilized seeds are sown in a plastic container (5 x 5 x 5 cm) containing horticultural soil (Kureha) that has been sterilized by autoclaving (121 ° C, 40 minutes). Cultivated under conditions of 60%, 16 hours light / 8 hours dark. Thereafter, the test strain was inoculated at 1 × 10 ⁸ cell / ml on the 10th day, and the cut leaves of the plant body were fed to the 3rd instar larvae 20 days later, and the feeding rate was measured.
Moreover, the endophytic infection rate of the plant body at this time was measured. Feeding tests were performed on individuals with confirmed infection.

Four. result

There was an individual whose infection was not confirmed in the endfight treatment section (table above).
From this study, it was clarified that Azospirillum sp. NITE BP-194 strain was inoculated into Arabidopsis thaliana to suppress pest feeding.

About rice insect resistance
Examination of inoculation effect in field cultivation of rice
1.1) Test 1: Drosophila damage, test method <br/> Rice varieties : Hoshinoyume endophyte strain: NITE BP-194 Inoculation date: May 26, 2005 Fixed planting date: May 28, 2005 Field: Pesticide-free cultivation test scale: 57.7 m ² , 3 seedling boxes (6 rows, about 1,340 plants)

1.2) Test 1: Results and discussion

  In the NITE BP-194 treatment area, the number of leaves damaged by the duck beetle decreased, and resistance to dromedary was confirmed.

2.1) Test 2: Dromedary damage, test method <br/> Rice variety: Kirara 397
Endophyte strain: NITE BP-194 Inoculation date: May 23, 2006 (1 x 10 ⁸ cells / ml of suspension of cells 500 ml / nursing box irrigation treatment)
Planting date: May 30, 2006 Field: Organic fertilizer, pesticide-free cultivation Test scale: Approximately 60 plants in each treatment area

2.2) Test 2: was measured each treated area 20 strains of Results and Discussion test group rice. The numbers in parentheses are relative numbers when the non-inoculated section is 100.

  In the NITE BP-194 treatment area, the number of leaves damaged by the duck beetle decreased, and resistance to dromedary was confirmed. There were many occurrences of drought beetles in this field, and the rate of damaged strains was 100% in all treatment areas.

3.1) Test 3: Dromedary damage, test method <br/> Rice varieties: Nanatsuboshi, Kirara 397
Endophyte strain: NITE BP-194 Inoculation date: Nanatsuboshi May 21, 2006, Kirara 397 May 23, 2006 (1 x 10 ⁸ cells / ml of suspension of suspension 500 ml (Box irrigation treatment)
Planting date: Nanatsuboshi May 24, 2006, Kirara 397 May 26, 2006 Field: Pesticide-free cultivation Test scale: 4 boxes for each treatment area (Article 8)
Two non-inoculation zones were prepared.

3.2) Test 3: Results and discussion

  In the NITE BP-194 treatment area, the number of leaves damaged by the duck beetle decreased, and resistance to dromedary was confirmed.

4.1) Test 4: stink bug damage, test method <br/> Rice variety: Kirara 397
Endophyte strain: NITE BP-194 Strain inoculation date: May 23, 2006 (1 x 10 ⁸ cells / ml of bacterial suspension 500 ml / nursing box irrigation treatment)
Planting date: May 26, 2006 Field: Pesticide-free cultivation Test scale: 76.8 m ^{2 for} each treatment area, 4 boxes (8 rows planted, about 1,790 strains)

4.2) Test 4: Results and discussion

  The number of colored damage grains due to stink bugs showed a decreasing trend in the NITE BP-194 test area.

About rice growth promotion, yield increase
1. Field cultivation test of rice inoculated with bacteria
1) Method <br/> Rice variety: Kirara 397
Endophyte strain: NITE BP-194 Inoculation date: May 23, 2006 (1 x 10 ⁸ cells / ml of bacterial suspension 500 ml / nursing box irrigation treatment)
Planting date: May 30, 2006 Field: Organic fertilizer, pesticide-free cultivation Test scale: Approximately 60 plants in each treatment area

2) Results and discussion 20 strains in each treatment area of the test rice were measured. The numbers in parentheses are relative numbers when the non-inoculated section is 100.

  As for the growth of rice, the number of stems and ears during growth increased in the NITE BP-194 inoculation group, and the growth was promoted. Regarding harvesting, drought increased in NITE BP-194 inoculation area.

2. Examination of the inoculation effect in the field cultivation of endfight inoculated rice
1) Method <br/> Rice varieties: Nanatsuboshi, Kirara 397
Endophyte strain: NITE BP-194 Strain inoculation date: Nanatsuboshi May 21, 2006, Kirara 397 May 23, 2006 (1 x 10 ⁸ cells / ml of bacterial suspension 500 ml (Box irrigation treatment)
Date of planting: Nanatsuboshi May 24, 2006, Kirara 397 May 26, 2006 Field: Pesticide-free cultivation Test scale: 76.8 m ^{2 for} each treatment area, 4 boxes (8 rows planted, about 1,790 strains) )
Two uninoculated wards were prepared and the average was calculated.

2) Results and discussion

On the 10th day after transplantation, plant height tended to be slightly lower in Kirara 397 inoculated with NITE BP-194, but the number of stems increased. After that, the number of stems during growth tended to be higher in the NITE BP-194 inoculation group than in the non-inoculation group, confirming that the tillering was promoted.
The yield increased for both Nanatsubo and Kirara 397 in the NITE BP-194 inoculation group.

Promoting soybean growth, increasing yield, and increasing nodulation
1. The purpose of this study was to investigate the effects of NITE BP-194, a new bacterium belonging to the genus Azospirillum, isolated from objective cultivated rice on growth promotion and yield increase in soybean.

2. Experimental method
2-1. Prototype product <br/> Soybean variety: Toyohomare 200 treatment areas
2-2. Farm field <br/> Farm field first year
2-3. Test bacteria
NITE BP-194 (Azospirillum novel bacterium)

2-4. Test Method Soybeans were sown in the field and cultivated in alleys. When there were about 1 to 3 true leaves, the bacterial solution prepared to 10 ⁸ CFU / ml was sprayed using a sprayer. Under normal management, growth and yield surveys were conducted during cultivation (57 days after sowing) and during the harvest period (135 days after sowing). The growth survey items were the number of leaves, stem length, and the number of established plants. In the yield survey, the number of arrivals was measured. The number of nodules was also measured.

3. Results
3-1. Growth Survey Results Table 13 shows the growth survey results on the 57th and 135th days after sowing. From the results on the 57th day, the leaf number and stem length of the NITE BP-194 inoculated group showed growth promotion compared to the control group. In addition, the 135-day harvest season survey showed that the NITE BP-194 treatment group showed growth promotion over the control group in all items.

  In addition, Table 14 shows the number of root nodules and the number of landings. NITE BP-194 treatment group had more pods and nodules than control group.

About increase in kale harvest
1. Examination of inoculation effect in field cultivation of endfight inoculated kale
1) Method <br/> Breed: End-of-house cultivar Endophite strain: NITE BP-194 Inoculation date: May 18, 2006 (1 X 10 ⁸ cells / ml of bacterial suspension 500 ml / nursing box irrigation processing)
Planting date: June 15, 2006, Hand-planted field: Sand, organic fertilizer, pesticide-free cultivation Test scale: More than 100 strains in each treatment area

NITE BP-194接種区で無接種区と比較してより生育が促進され、収量が増加した。 2) Results and discussion

In the NITE BP-194 inoculation group, the growth was further promoted and the yield increased compared to the non-inoculation group.

Onion yield increase
1. Examination of inoculation effect in field cultivation of endfight inoculated onion
1, Method <br/> Onion variety: North maple 2000
Endophyte strain: NITE BP-194 Strain inoculation date: May 2, 2006 (1 x 10 ⁸ cells / ml of bacterial suspension 500 ml / nursing box irrigation treatment)
Planting date: May 4-7, 2006 Field: Conventional cultivation test scale: 448 strains (224 strains x 2) in each treatment area

2) Results and discussion

In Northern Maple 2000, the leaf sheath diameter tended to increase in the NITE BP-194 inoculation group. Regarding the plant height, a slightly large tendency was seen in the NITE BP-194 inoculation area, but the level was almost the same.
As for the harvest, the yield increased in the NITE BP-194 inoculation area.

Claims (10)

  Contributes pest resistance to cruciferous plants, including the step of artificially infecting cruciferous plants with bacteria that belong to the genus Azospirillum and have the ability to symbiotize in cruciferous plants and impart pest resistance to the plants how to.   Increasing the yield of cruciferous plants, including the step of artificially infecting the cruciferous plants with bacteria that belong to the genus Azospirillum and have the ability to symbiotically in the cruciferous plants and increase the yield of the plant leaves How to make.   Giving pest resistance to gramineous plants, including the step of artificially infecting gramineous plants with bacteria that belong to the genus Azospirillum and have the ability to symbiotically live in gramineous plants and impart pest resistance to the plants how to.   A method of promoting the growth of gramineous plants, comprising the step of artificially infecting the gramineous plants with a bacterium belonging to the genus Azospirillum and having the ability to coexist in the gramineous plants and promote the growth of the plants.   A method for increasing grain yield in gramineous plants, comprising the step of artificially infecting gramineous plants with a bacterium belonging to the genus Azospirillum and having the ability to symbiotically grow in the grass family and increase the grain yield in the plant. .   A method of promoting leguminous plant growth, comprising the step of artificially infecting legumes with a bacterium belonging to the genus Azospirillum and having the ability to symbiotically grow in the legumes and promote the growth of the plants.   Increasing the number of leguminous plants, including the step of artificially infecting legumes with bacteria that belong to the genus Azospirillum and have the ability to symbiotically in the leguminous plants and increase the number of these plants. How to make.   A method for increasing the number of root nodules in legumes, comprising the step of artificially infecting legumes with a bacterium belonging to the genus Azospirillum and having the ability to symbiotically in the legumes and increasing the number of nodules in the plants .   A plant belonging to the genus Azospirillum, including a step of artificially infecting a lily family plant having a bulb with a bacterium that has the ability to symbioticly in the lily family plant having a bulb and increasing the yield of the bulb in the plant. To increase the yield of bulbs.   The method according to any one of claims 1 to 9, wherein the bacterium is a novel genus Azospirillum (accession number NITE BP-194) or a mutant strain thereof.