JP2010233509A - Method for raising and harvesting rice plant at low cost in short period, using blue led, and selection of system suitable for the method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for cultivating and harvesting rice plants under an artificial environment in a short period at a low cost. <P>SOLUTION: The method for cultivating and harvesting rice plants includes cultivating a plurality of kinds of rice plants in a day-length condition of 10 h light period, using blue light LED, and as a result, a heading time becomes earlier than that of the same condition with white light in a certain rice plant (Nipponbare, Norin No.8), and also when a blooming promoting gene such as Hd1 gene and Ehd1 gene is introduced, the number of grains of one head decreases. Subsequently, the method includes cultivating rice plants by changing the planting density, and as a result, compared to rice plants raised at a normal planting density, rice plants raised at an overcrowded density have the total number of unhulled rice per unit area, larger than at a normal planting density, and the number of heads per individual decreases. Furthermore, when cultivating rice plants by irradiating it with blue light and changing a planting density, dense planting enables more efficient cultivation even with single blue light. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for cultivating and harvesting rice at a low cost in a short period of time using a blue LED, and selection of a line suitable for this method.

Cultivation of rice in an artificial environment requires strong light conditions for a long time until harvest, and it has been found that cultivation with a light source such as a sodium lamp is difficult due to its light quality. Along with the development and popularization of a strong white light lamp with a broad spectrum called a metal halide lamp, it has become possible to cultivate until harvest in an artificial environment. However, optimization of cultivation conditions in an artificial environment and selection of optimum lines for the long-term cultivation of rice from seeds and seedlings to harvesting have not been performed. On the other hand, because of the advancement of genetic engineering technology and the fact that rice endosperm (rice part) is very good at mass production of foreign proteins, it is a high-value substance in the endosperm of genetically modified rice Industrialization is being studied for the production of non-patent material (Non-patent document 1: Wakasa et al., (2009)), but it is not affected by the problem of PA (public acceptance) or unstable natural environment. For safe production, cultivation in an artificial environment is considered important.
It is known that blue light has a specific physiological effect on plant growth, and many papers have been reported mainly in Arabidopsis (for example, Non-Patent Document 2: Ahmad & Cashmore (1993), Non-Patent Document). 3: Guo et al. (1999), Non-patent document 4: Christie et al. (1998), Non-patent document 5: Somers et al. (1998), Non-patent document 6: Somers et al. (2000), Non (Patent Literature 7: Kinoshita et al. (2001), Non-Patent Literature 8: Kagawa et al. (2001), Non-Patent Literature 9: Imaizumi et al., (2005)). Analysis of mutants using the model plant Arabidopsis thaliana has reported that the effects of blue light on flower bud formation promotion, photomorphogenesis, phototropism, circadian clock or stomatal opening and closing are remarkable. For example, it has been clarified that cryptochrome blue photoreceptors act on flower bud formation and photomorphogenesis, and phototropin blue photoreceptors act on phototropism and stomatal opening and closing. It was revealed that new blue photoreceptors with a box, such as ZTL and FKF1, play a role in circadian clock and flower bud formation. Among such basic researches, there have been reports on techniques using blue LED light for efficient seedling growth and flower bud promotion as supplementary light, mainly in Arabidopsis and recent cruciferous plants. . Also, rice, which is a major crop in Japan, has been reported to have an effect of promoting the flowering of blue light as supplementary light and the effect of preventing the length of seedlings when growing seedlings with a single blue light (for example, Patent Document 1: Japanese Patent Application Laid-Open No. 2002-2002). 345337). However, no technology has been reported so far in which blue light is used as a main light source for growing crops from sowing to harvesting. In addition, no attempt has been reported so far to find a suitable line for artificial environmental cultivation based on genetic lineage differences based on natural variation.

JP2002-345337

Wakasa Y, Ozawa K, Takaiwa F. J Biosci Bioeng. 2009 Jan; 107 (1): 78-83 Ahmad & Cashmore Nature. 1993 Nov 11; 366 (6451): 162-6 Guo et al., Science. 1998 Feb; 279 (5355): 1360-1363 Christie et al., Science. 1998 Nov 27; 282 (5394): 1698-701 Somers et al., Science. 1998 Nov 20; 282 (5393): 1488-90 Somers et al., Cell. 2000 Apr 28; 101 (3): 319-29 Kinoshita et al., Nature. 2001 Dec 6; 414 (6864): 656-60 Kagawa et al., Science. 2001 Mar 16; 291 (5511): 2138-41 Imaizumi et al., Science. 2005 Jul 8; 309 (5732): 293-7

  Rice is said to require a larger amount of light for growth than other crops, and in order to grow rice with good reproducibility in an artificial environment etc., cultivation with a metal halide lamp as a light source and light of about 500 μmol or more is essential. It was thought. For this reason, rice cultivation in an artificial environment or the like was extremely difficult both in terms of cost and technically. Therefore, a method for cultivating and harvesting rice in an artificial environment at a low cost for a short period of time has been demanded.

Multiple days of rice (NIP, NIP-Hd1, N8, N8-SE5, N8-SE5-OsGI, N8-OsGI-Hd1, N8-OsGI) , T65, T65 + Hd1, T65 + Ehd1, T65 + Hd1 + Ehd1). Here, the names on the left, NIP, N8, and T65 indicate Nihonbare, Norin No. 8, and Taichung No. 65. Plus and minus indicate the presence or absence of a functional gene in the left genetic background. Show. As a result, some rice (Nippon Hare (NIP), Norin No. 8 (N8)) had earlier heading season than the same condition with white light. This result shows the flowering promotion effect by blue light. In addition, the number of spikelets was greatly different between strains, and N8 was 10 hours longer than NIP and suitable for cultivation under dense planting conditions. From this result, it is predicted that the genetic background is important for increasing the number of spikelets, which is a very large factor that determines yield.
Next, when we examined the cultivation of rice at a very extreme day length of 20 hours, the Hd1 gene was shown to act on flowering suppression, and was observed under the day length condition of 10 hours light period. Such flowering promotion was not observed except in phytochrome-deficient lines with se5 mutation.
Moreover, when rice was cultivated under the day length condition of 10 hours light period or 14 hours light period using white light, the number of spikelets per short day condition tended to be large. It was also observed that the number of spikelets decreased when the Hd1 gene or Ehd1 gene was introduced (the ability of Hd1 to promote flowering was observed only under short-day conditions).
Subsequently, when rice was cultivated at different planting densities, rice grown at a denser planting density than normal planting density compared to rice grown at a normal planting density had a greater total fir per unit area. The number was high and the number of spikes per individual decreased. In other words, it became clear that the number of ears per individual decreased when the tillering was suppressed by dense planting, but the total number of fir increased as the total number of ears increased. This is a result which means that space saving is realized by dense planting when cultivating rice in an artificial environment.
Furthermore, when rice was cultivated by irradiating it with blue light and changing the planting density, it was shown that dense planting can be cultivated more efficiently even in blue light monochromatic.
From the above results, it is predicted that even if cultivation is performed with blue light, it is comparable to red light in terms of yield.
That is, the present invention provides the following [1] to [12].
[1] A method for producing rice, wherein rice is cultivated by irradiation with blue light under dense planting conditions and short day conditions.
[2] The method according to [1], wherein the wavelength of blue light is 400 nm to 500 nm, and the photon flux density (light intensity) is 50 to 500 μmol / m ² / sec.
[3] The method according to [1] or [2], wherein the blue light irradiation is 8 to 24 hours / day.
[4] The method according to [3], wherein the blue light irradiation is 8 to 13 hours / day.
[5] The method according to any one of [1] to [4], wherein the flowering promoting gene is deficient, the function of the flowering promoting gene is inactive, or the rice has a flowering suppression gene having activity. .
[6] The method according to [5], wherein the flowering promoting gene is selected from the group consisting of an Hd1 gene, an Ehd1 gene, an OsGI gene, an Hd3a gene, an RFT1 gene, an Ehd2 gene, and an OsMADS50 gene.
[7] The method according to [5], wherein the flowering suppression gene is selected from the group consisting of Lhd4 gene, Hd6 gene, and Hd5 gene.
[8] The method according to any one of [1] to [7], further irradiating light having a wavelength of 500 nm to 770 nm.
[9] A method for screening rice having a large number of spikelets, comprising a step of cultivating rice by irradiating blue light under dense planting conditions and a step of selecting rice having a large number of spikelets.
[10] The method according to [9], wherein the wavelength of blue light is 400 nm to 500 nm, and the photon flux density (light intensity) is 50 to 500 μmol / m ² / sec.
[11] The method according to [9], wherein the blue light irradiation is 8 to 13 hours / day.
[12] The method according to any one of [9] to [11], further comprising irradiating light having a wavelength of 500 nm to 770 nm.

  In the development of genetically modified rice, it is required to grow rice in an environment that is not affected by the environment from the outside, that is, an artificial environment isolated from the outside. The invention provided by the present invention makes it possible to grow rice from sowing to harvest with good reproducibility with a low-power light source, compared to conventional rice cultivation techniques in an artificial environment. In addition, there are several genotypes suitable for cultivation in densely planted artificial environments that can contribute to an increase in the number of spikelets per cultivation period while ensuring yields comparable to the yield per isolated area in the field. Identification has dramatically increased the cost efficiency of rice harvesting in artificial environments. The invention provided by the present application can be applied to various rice resources and is very effective in the development and research of new genetically modified rice.

It is the figure which compared the heading time on high-intensity LED blue light and 10-hour day length conditions. It is the figure which compared the above-ground part weight on high-intensity LED blue light and 10-hour day length conditions. It is the figure which compared the number of single ears of the main stem ear on high-intensity LED blue light and 10-hour day length conditions. It is the figure which compared the heading time on blue light and 20-hour day length conditions. It is the figure which compared the number of one ear grain with white light. (A) 10-hour light period 14-hour dark period short-day condition, (B) 14-hour light period 10-hour dark period long-day condition. It is a correlation figure of the number of head spikes and heading date. Symbols indicate the genotype and cultivation conditions and are shown at the top of the figure. It is the figure and photograph of the examination result of the cultivation conditions in a closed artificial environment using the cultivar Nipponbare. The yield of various fertilizers under short-day conditions and cultivation conditions was investigated using Nipponbare. The pot size is 227cm ² (diameter 17cm). (B) to (C), for example, SD1-3 indicates that the conditions are 10h light 14h dark ( SD ), fertilizer 1g ( 1 ), 3 plants / pot ( 3 ) . The same applies to other descriptions (SD3-3). (A) Photograph before harvesting when 3,24,30,36 individuals were grown in the illustrated fertilizer for each pot, (B) Comparison of dry weight of above-ground parts, (C) Comparison of number of ears, (D ) Comparison of the total number of fir on the ear. It is the figure and photograph of the examination result of the difference between varieties of Nipponbare and Takanari (high-yielding indica varieties) in examination of cultivation conditions under a closed artificial environment. (A) Comparison figure of total number of fir attached to ear, (B) Comparison figure of number of one ear, (C) Photograph of Nipponbare and Takanari ears grown under the same conditions.

  The present invention relates to a rice production method in which rice is cultivated by irradiation with blue light under dense planting conditions and short day conditions.

  In the present invention, rice is cultivated in an artificial environment. In an artificial environment, rice can be cultivated using soil as in the field. There is no restriction | limiting in particular in the kind of soil used, The thing similar to a farm field is used. In addition, soil is not necessarily required for cultivation of rice in an artificial environment, and hydroponics is also possible, and various types of carriers such as rock wool, glass beads, and porous plastic are possible (“water” Response of NERICA Rice to Phosphorus-Deficient Conditions in Tillage and Soil Cultivation ”, Chiharu Sone, Makoto Tsuda, Yoshihiko Hirai, Journal of the Crop Science Society of Japan (Abstracts and Materials) Vol. 226 (2008) No. SPACE pp .184-). About hydroponics, the cultivation used for water about 15 cm from the stem base is often seen in the field. In an artificial environment, in order to prevent salt formation, there are many cultivations in which the water height is lower than the height corresponding to the ground. However, various rice resources include rice that can be cultivated in various ways. From the extent that the roots are in contact with water, rice that can grow even when the whole body is immersed in water, such as floating rice and flood-resistant rice, is also known. The possible water environment is different ("Research and application using rice diversity", Motoyuki Tsuji, Annual Report of the Crop Society of Japan (Abstracts and Materials), Vol. 227 ( 2009) No. SPACE pp.392-, `` Sub1A is an ethylene-response-factor-like gene that confers submergence tolerance to rice. '' Xu K, Xu X, Fukao T, Canlas P, Maghirang-Rodriguez R, Heuer S, Ismail AM, Bailey-Serres J, Ronald PC, Mackill DJ. Nature. 2006 Aug 10; 442 (7103): 705-8.). The temperature environment has a growth stage that is susceptible to low temperatures after the formation of young ears and after heading. At that stage, 18 ° C or higher is necessary, but at the time of sowing or growth, it can be 15 ° C or higher. The upper limit is good in Japan's midsummer climate, 40 ° C or less is appropriate, and more preferably, cultivation at 20-30 ° C is preferable ("Evaluation of cold tolerance in booting and flowering periods in Indian rice") Akitoshi Goto, Hideki Sugawara, Akiko Shigemune, Kiyoyuki Miura, Journal of the Crop Science Society of Japan, Vol. 77 (2008) No. 2 pp.167-173).

  In the present invention, rice is cultivated under dense planting conditions. Usually, 0.225 to 0.9 rice seedlings are transplanted per 270 cm 2. In a normal field, 3 to 6 seedlings are mechanically transplanted to about 30 cm x 15 cm (or 30 cm). On the other hand, the `` dense planting condition '' of the present invention means that the number of seedlings to be transplanted is larger than the normal number of transplants, specifically, 3 to 42 per 270 cm 2, preferably It means 12 to 36, more preferably 23 to 36, but is not limited thereto.

  Examples of the day length condition for growing rice in the present invention include a long day condition and a short day condition, but the short day condition is preferable. In the present invention, the long day condition is a condition in which the sunshine time of one day is 13.5 hours or more. In the present invention, the “short day condition” means a condition in which the daily sunshine time is less than 13.5 hours, preferably the daily sunshine time is 8 to 13 hours, more preferably 10 to 12 hours. It's time. The light period of the short day condition in this embodiment is 10 hours, but is not limited thereto. Moreover, although it is preferable that it is a short day condition at the time of flower bud formation, it is not restrict | limited to this.

In the present invention, rice is cultivated by irradiation with blue light. The wavelength of blue light used in the present invention is 400 nm to 500 nm, preferably 450 nm to 500 nm. In this embodiment, blue light having a peak wavelength of 465 to 470 nm is used, but the present invention is not limited to this.
In the present invention, a light emitting diode (LED), a fluorescent lamp, a laser light source, or the like can be used as a blue light source. In view of the characteristics such as cost and long life, it is preferable to use the LED in the present invention, but the present invention is not limited to this.
Photon flux density of the blue light used in the present invention is preferably 50~500μmol / m ² sec, more preferably 100~500μmol / m ² sec, even more preferably 120~300μmol / m ² sec. In the present embodiment, the light quantity is about 120 [mu] mol / m ² sec at the height of the soil is about 300 [mu] mol / m ² sec in the vicinity of plants, but is not limited thereto.

  The rice used in the present invention is preferably rice having a flowering suppression gene that is deficient in the flowering promotion gene, inactivated in the function of the flowering promotion gene, or active. Rice lacking a flowering promoting gene means rice that does not have the flowering promoting gene itself. Moreover, the rice in which the function of a flowering promotion gene is inactivated means a rice having a flowering promotion gene, but the flowering promotion function is inactivated by gene mutation or RNAi. Furthermore, the rice having a flowering suppression gene having activity means rice having a flowering suppression gene having an activity of suppressing flowering.

As flowering promoting genes, Hd1 gene (under short-day condition cultivation) (Patent No. 3660967, Yano et al., Plant Cell 2000 Dec; 12 (12): 2473-2484), Ehd1 gene (Patent No. 3912202, Doi et al. Genes & Dev. 2004 Apr 15; 18 (8): 926-36), OsGI gene (in short-day cultivation) (Hayama et al., Plant Cell Physiol. 2002 May; 43 (5): 494-504) , Hd3a gene (JP 2002-153283 A, Kojima et al. Plant Cell Physiol. 2002 Oct; 43 (10): 1096-105), RFT1 gene (Patent No. 3823137, Kojima et al. Plant Cell Physiol. 2002) Oct; 43 (10): 1096-105), Ehd2 gene (Matsubara et al., Plant Physiol. 2008 Nov 12; 148 (3): 1425-35), OsMADS50 gene (Lee et al., Plant J. 2004 Jun) ; 38 (5): 754-64), but is not limited thereto.
As a flowering suppression gene, Lhd4 gene (Japanese Patent Laid-Open No. 2004-290190), Hd6 gene (only in long-day condition cultivation) (Japanese Patent No. 3660966, Takahashi et al., PNAS. 2001 Jul 3; 98 (14): 7922-7) and Hd5 gene (Japanese Patent Laid-Open No. 2005-110579), but are not limited thereto.

The Hd1 gene encodes an evolutionarily conserved transcription factor, and is a flowering gene of rice having multiple functions that functions as a flowering promoting factor under short-day conditions and as a flowering inhibitory factor under long-day conditions. Breeding studies have revealed that it is the same locus as the Se1 locus.
The Ehd1 gene is a transcription factor that encodes a B-type response regulator.It functions to promote flowering mainly in short-day cultivated conditions, but it also promotes long-day cultivated conditions. Shows the phenotype of not flowering
The OsGI gene is a gene constituting the circadian clock of rice and promotes flowering under short-day conditions. There is almost no effect on flowering under long day conditions.
The Hd3a gene encodes a low peptide, functions as a florigen, moves through the leaf vascular bundle, and induces flower bud formation at the shoot apex. Mainly functions to promote flowering under short-day conditions.
The RFT1 gene encodes a low peptide, functions as a florigen, moves through the leaf vascular bundle, and induces flower bud formation at the shoot apex. Mainly functions to promote flowering under long day conditions.
The Ehd2 gene is an ortholog of maize Id1 and is a gene that promotes flowering of rice.
The OsMADS50 gene is an ortholog of the SOC1 gene of Arabidopsis thaliana and is a gene that promotes flowering of rice.
The Lhd4 gene is a flowering suppression gene with a CCT motif, and is a homologue of the VRN2 gene required for wheat vernalization, but its biochemical function is still unclear. It is expressed mainly under long-day conditions, and exhibits a very strong flowering suppression ability under cultivation under long-day conditions. Even in short-day condition cultivation, it has a weak but inhibitory effect. It is the same gene as Ghd7 recently published (Xue et al., Nat Genet. 2008 Jun; 40 (6): 761-7).
The Hd6 gene encodes the casein kinase 2 gene. Suppresses flowering of rice under long-day conditions, but does not affect flowering under short-day conditions.
The Hd5 gene is one of the HAP3 transcription factors and suppresses flowering of rice mainly under long-day conditions.

  Therefore, in the present invention, rice lacking the Hd1 gene, Ehd1 gene, OsGI gene, Hd3a gene, RFT1 gene, Ehd2 gene, OsMADS50 gene, etc., or rice whose function is inactivated, or Lhd4 It is preferable to use rice having relatively active genes, Hd6 genes, Hd5 genes and the like, but is not limited thereto.

  In addition to blue light, the present invention further provides white light (red light / near infrared light) having a wavelength of 500 nm to 770 nm, preferably white light having a wavelength of 600 nm to 770 nm, and red light having a wavelength of 650 nm to 700 nm. Or a method of cultivating rice by irradiating near infrared light having a wavelength of 700 nm to 770 nm. The ratio of the blue light to the other light is about zero to the same level, preferably about half to the same level, more preferably about the same level, but is not limited thereto. Methods for cultivating rice using both blue light and other light are described in detail in JP-A-H11-196671, JP-A-2002-345337, and the like.

  The method of the present invention makes it possible to cultivate rice having a large number of spikelets. “Number of grains per ear” refers to the number of grains of rice obtained from one ear. Under the dense planting conditions of the present invention, only about one ear is grown per individual, so “number of grains per ear” can also be regarded as “number of grains obtained from one individual”. In addition, when two or more ears are produced per individual, “number of ears” measures the total number of ears per ear and indicates a number divided by the number of ears. The number of spikelets is one of the factors contributing to the yield in dense planting.

  The present invention also provides a method for screening rice having a large number of spikelets, comprising a step of cultivating rice by irradiating blue light under dense planting conditions and a step of selecting rice having a large number of spikelets. The specific mode of cultivation in which rice is irradiated with blue light under dense planting conditions is as described above.

  In the stage of selecting rice, the determination of whether the number of spikelets is large can be used as a control, for example, the yield of “Nipponbare”, which is generally used for studying characteristics such as rice yield, It is not limited to this.

  In addition, all prior art documents cited in the present specification are incorporated herein by reference.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, the scope of the present invention is not limited to the aspect described in these Examples.

Biotron equipped with a panel using a high-brightness blue light LED (Toyoda Gosei, model name E1L53-AB1A6-05 (half-value width is 25 nm, peak wavelength is 465 to 470 nm)) NC1000). On the Biotron, 12 8x8 LED panels are installed directly downward, and 5 identical panels are installed diagonally downward on the left and right. A pot of 17cm (227cm ² ) diameter (with 3 holes to allow water to pass through the bottom), 1 liter of Bonsol No. 2 soil (Sumitomo Chemical Co., Ltd.), and non-fertilizer cultivation soil 1 liter was put and 10-25 seeds were sown. 10 hours light period (9:00 to 19:00) 14 hours dark period (19:00 to 9:00) day condition (12 hours (8:00 to 20:00) noon temperature 30 degrees, night 12 hours (20:00 to 8:00) temperature was 25 degrees), and rice was cultivated under the conditions of dense planting (around 20 individuals per pot), resulting in few tillers and 1 individual It was cultivated with 1 to 2 shoots, and the number of ears was 1 to 2 per individual, and many were 1 ear .. 50 days after sowing, fertilization (Advanced Chemical Hilac No. 444 Mitsui) ) 3 g per pot.
The amount of light emitted by the LED was about 300 μmol / m ² sec near the plant, and the soil height of the pot was about 120 μmol / m ² sec.
The materials used were the Japanese rice cultivar Nipponbare (NIP) and its hd1 mutant (NIP-Hd1), the Japanese rice cultivar Norin 8 (N8) and its se5 mutant N8-SE5 (SE5 is phytochrome light receptor) No. 65, Taichung 65, a rice cultivar that lacks the function of the Ehd1 flowering gene. (T65) and T65 + Hd1, T65 + Ehd1, and T65 + Hd1 + Ehd1 into which Hd1 and Ehd1 flowering genes were introduced by transformation (see FIG. 1). When a plurality of spikes appeared per individual, the number of spikelets of the spike of the main stem was investigated.

FIG. 1 shows the heading period, FIG. 2 shows the weight of the above-ground part (biomass), and FIG. 3 shows the number of grains per ear, showing the average value of 5 to 10 individuals.
FIG. 1 is a diagram showing the heading time of each rice in blue light with a 10-hour day length. This result remarkably shows the flowering promotion ability of blue light. Nihonbare (NIP) and Norin No. 8 (N8) take about 60 days (not shown) with white light from a metal halide lamp of the same day length, but about 45 days with blue light. The photochrome se5 mutant has a heading date of more than 40 days under the same conditions with white light in a metal halide lamp (not shown). In other words, it was clarified that in the case of 10 hours of blue light, normal varieties are prematurely bloomed without the suppression of flowering by light signals via phytochrome. It was also found that Hd1, Ehd1 and OsGI work to promote flowering under these conditions.
FIG. 2 is a diagram showing the above-ground weight (biomass). The heading time (FIG. 1) and the above-ground weight (FIG. 2) showed a very strong correlation. From these results, it is considered that there is no interstrain difference in photosynthetic capacity other than strains with se5 mutations that are abnormal in chloroplast differentiation, and daily photosynthesis is accumulated and reflected in the above-ground weight.
FIG. 3 is a diagram showing the number of ears of main stems. As shown in Fig. 3, the number of spikelets is greatly different between strains, and it is considered that Norin No. 8 (N8) is more suitable for cultivation under the conditions of 10 hours day length and dense planting than Nihonbare (NIP). It is done. In addition, in terms of the presence or absence of the gene, under this condition, the decrease in the number of single grains due to flowering promotion by the Hd1 gene was observed between multiple lines, NIP and NIP-Hd1, N8-OsGI and N8-OsGI-Hd1, T65 + Hd1 And T65, T65 + Ehd1 and T65 + Ehd1 + Hd1. In other words, genetic background is expected to be important for increasing the number of spikelets, which is a very important factor that determines yield. As an example, in this example, it was observed that a genetic background that no Hd1 gene was present was suitable.

  Next, in order to confirm the relationship between the cultivation cost per unit time and the yield, cultivation was carried out with a 20-hour day length in order to examine whether flowering promotion similar to the 10-hour day length could be seen even with a long day length. It was. The same line as that used in Example 1 was cultivated by adding a line in which a Hd1 mutation was introduced into a hayamasari, a Hokkaido variety. Other cultivation conditions such as the amount of blue light and dense planting conditions are the same as in Example 1.

  As a result, it was shown that Hd1 acts on flowering suppression in a manner consistent with previous findings (FIG. 4). In addition, flowering promotion as observed in Example 1 could not be observed without phytochrome se5 mutation. On the other hand, in spite of the absence of the se5 mutation, the Hd1 deficient line of Hayamasari flowered in about 70 days. The early flowering of this line, even with a very extreme day length of 20 hours, is thought to be due to the deletion of the Lhd4 gene.

Next, the number of spikelets in white light was examined. The seeds were cultivated by irradiation with a metal halide lamp (white light, 500 umol E Japan Battery MT2000B-P / BH (2 kW)). Three individuals were cultivated per 1 pot (270 cm ² ). The sunshine hours in the 10-hour light period are from 8:00 to 18:00, and the temperature change is 28 ° C from 8:00 to 20:00 and 24 ° C from 20:00 to 8:00. The growth chamber has a floor area of 8 m ² and a 50 cm x 90 cm container placed on the floor in an artificial environment where 8 metal halide lamps are irradiated from a height of 2 m 45 cm. A total of 4 lines obtained from the mating progeny between the lines transformed with the flowering genes Hd1, Ehd1, Hd1 + Ehd1 and the lines having a single gene were cultivated 4 times independently. The day length condition was cultivated under two conditions, a short day condition of 10 hours light period 14 hours dark period and a day length condition of 14 hours light period 10 hours dark period.

  As a result, the same tendency as the blue light cultivation was observed for the number of spikelets, although there was fluctuation at each time. That is, it was observed that the number of spikelets decreased by introducing Hd1, Ehd1, and Hd1 + Ehd1 flowering genes in a form that was not greatly affected by the shift in heading time (FIGS. 5 and 6). In particular, the decrease in the number of spikelets when two genes are introduced is remarkable. Judging from this result, it can be seen that flower bud formation without Ehd1 increases the number of spikelets. From these results, it is considered that flower bud formation in a state without Hd1 or Ehd1 function, that is, a state in which the ability to promote flower bud formation by a flowering gene is weak, is important for increasing yield. It is also a noteworthy result that the number of spikelets per short day condition tends to be large. According to this example, it was shown that cultivating a plant under short-day conditions was effective in increasing the number of spikelets during flower bud formation. From this result, even under the blue light condition described in Example 1, it is considered that the cultivation under the short day condition is cost-effective.

  Next, we examined the importance of dense planting in an artificial environment. The seeds were cultivated by irradiation with a metal halide lamp (white light, 500 umol E Japan Battery MT2000B-P / BH (2 kW)). The same growth chamber as in Example 3 was used for the experiment using the same container. Other cultivation conditions such as day length are the same as in Example 3. Rice seedlings using Nipponbare seeds were nurtured, and then planted by changing the number of transplanted individuals such as 3, 24, 30, and 36 individuals per pot. Fertilizer (advanced Kasei Hilac No. 444 Mitsui) is given 1g, 3g, or 5g per pot, and rice is grown until harvest, and the total dry weight, the number of ears, and the number of fir on the ears are examined. (FIG. 7). As a result, the total number of fir of rice grown under the conditions of 24 individuals, 30 individuals, and 36 individuals per pot that is more dense than the normal planting density, compared to rice grown under conditions of 3 individuals per pot of ordinary planting density Was 2 to 3 times, and the number of spikes per individual decreased. In other words, it became clear that the number of ears per individual decreased when the tillering was suppressed by dense planting, but the total number of fir increased as the total number of ears increased. This indicates that dense cultivation is efficient in cultivation in an artificial environment, and that increasing the number of spikelets is important for cultivation in an artificial environment. Next, a similar experiment was performed using Nipponbare and the Indica type cultivar Takanari, which is known as a high-yield variety (FIG. 8). As a result, even in Takanari, the results showed that dense planting increased the total number of fir, and Takanari confirmed that the number of spikelets was larger than that of Nipponbare and the number of fir per pot was also large. This experimental result shows that the number of spikelets is large as a factor controlling the yield.

As in Example 1, Biotron (main unit is a specially equipped panel using a high-brightness blue light LED (Toyoda Gosei, model name E1L53-AB1A6-05 (half-value width is 25 nm, peak wavelength is 465 to 470 nm)) , YELA Tokyo Rika Instrument Co., Ltd. NC1000), 17cm (227cm ² ) diameter pot (with 3 holes in the bottom to allow water to pass), bottom, Bonsol No. 2 1 liter of industry, 1 liter of non-fertilizer soil on top, 10 to 25 seeds sown 10 hours light period (9:00 to 19:00) 14 hours dark period (19:00 to 9:00) ) Under the conditions of day length (12 hours (8: 00-20: 00) at noon, 30 degrees Celsius, and 12 hours at night (20: 00-8: 00) 25 degrees Celsius) .
The yield was compared between 6 individuals under sparse planting conditions and 26 plants under dense planting conditions per cultivation area (0.0227 m ² ). There are few tillers, and 7 ears appeared in sparse planting and 26 ears in dense planting. The sowing date was December 26, 2008, the heading was after February 10, and the water was drained on March 10, and the number of grains and the number of fruit seeds were measured 10 days later. Fertilization was not performed after sowing.
As in Example 1, the amount of light emitted by the LED was about 300 μmol / m ² sec near the plant body, and the LED light source being turned on consumed about 180 w of power.

As a result of measuring the total number of grains, in sparse planting, the total number of grains per pot was 172 grains, of which 120 seed grains were seeded. On the other hand, in dense planting, the total number of grains per pot was 491, of which 269 were nuts. The measurement results of each ear are shown in Table 1. This result shows that dense planting can be efficiently cultivated even in the blue light monochromatic. In addition, the yield of this cultivation method was found to be about 12000 grains / m ² (269 grains / 0.0227 m ² ) in a cultivation period of about 70 days. With white light, there is a result that the yield is improved even with further dense planting (Example 4). Therefore, it is considered possible to further improve the cultivation efficiency by blue light cultivation.

Claims (11)

A rice production method in which rice is cultivated by irradiating blue light under dense planting conditions and short-day conditions. The method according to claim 1, wherein the wavelength of blue light is 400 nm to 500 nm, and the photon flux density (light intensity) is 50 to 500 μmol / m ² / sec. The method according to claim 1 or 2, wherein the irradiation with blue light is 8 to 24 hours / day. The method according to claim 3, wherein the irradiation with blue light is 8 to 13 hours / day. The method according to any one of claims 1 to 4, wherein the flower-promoting gene is deficient, the function of the flower-promoting gene is inactive, or the plant has a flowering-suppressing gene having activity. 6. The method according to claim 5, wherein the flowering promoting gene is selected from the group consisting of an Hd1 gene, an Ehd1 gene, an OsGI gene, an Hd3a gene, an RFT1 gene, an Ehd2 gene, and an OsMADS50 gene. The method according to claim 5, wherein the flowering suppression gene is selected from the group consisting of Lhd4 gene, Hd6 gene, and Hd5 gene. Furthermore, the method of any one of Claims 1-7 which irradiates light with a wavelength of 500 nm-770 nm. A method for screening rice having a large number of spikelets, comprising a step of cultivating rice by irradiating blue light under dense planting conditions and a step of selecting rice having a large number of spikelets. The method according to claim 9, wherein the wavelength of blue light is 400 nm to 500 nm, and the photon flux density (light intensity) is 50 to 500 μmol / m ² / sec. The method according to claim 9, wherein the irradiation with blue light is 8 to 13 hours / day.