Wakame thallus and method for cultivating the same

Abstract

To provide a wakame thallus and a method for cultivating the same, enabling reduction of a life cycle during wakame cultivation and promoting production of useful wakame strains.SOLUTION: In one aspect, provided are a wakame thallus having a frond length of 8 cm or more and 20 cm or less and having a sporophyll, and a method for cultivating the same.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to wakame algae and a method for cultivating the same. [Background technology]

[0002] Seaweed is an excellent biological resource because it grows large, allowing for efficient harvesting and reducing land use. For example, wakame (Undaria pinnatifida, Phaeophyceae, Laminariales, Phaeophyceae, Undaria genus) is one of the most useful biological resources for food. Wakame is required to be adaptable to a wider range of environments, and from the perspective of negative emissions, it is also required to have a higher carbon content and more efficient photosynthesis. Therefore, it is desirable to develop strains that exhibit these useful characteristics as biomass.

[0003] The wakame seaweed life cycle consists of a gametophyte generation, in which a gametophyte develops from a zoospore, grows, matures (i.e., forms archegonia and antheridia), and then fertilizes. The sporophyte generation, in which a gametophyte develops after fertilization, grows, and matures (i.e., forms sporophytes), and then releases zoospores, is completed after fertilization. The heterogeneous life cycle, consisting of gametophyte development → gametophyte growth → gametophyte maturation → fertilization → sporophyte development → sporophyte growth → sporophyte maturation → zoospore release, typically takes one year to complete. In the typical wakame seaweed life cycle, the gametophyte generation develops during high water temperatures (e.g., from spring to autumn in Japanese coastal waters) and the sporophyte generation develops during low water temperatures (e.g., from autumn to spring in Japanese coastal waters). However, due to the long and complex life cycle described above, wakame seaweed breeding and seed management have not been actively pursued.

[0004] Wakame cultivation in the waters off Japan is often carried out as follows. First, in the fall, zoospores are attached to cultivation ropes, and gametophytes are grown. After fertilization and germination, spores emerge, and the cultivation ropes are placed in deep, calm water (i.e., with reduced wave impact) until the leaf length reaches approximately 2-3 cm. This calm environment is necessary for the appressoria of the young sporophytes to develop and attach to the rope. Once the leaf length reaches approximately 2-3 cm, the cultivation ropes are clamped in shallow cultivation facilities, and full cultivation begins. In full cultivation, the water currents caused by the waves continuously supply fresh seawater to the sporophytes, promoting their growth.

[0005] However, in recent years, rising water temperatures in autumn, the seedling production season, have made it difficult to harvest seedlings from natural algae. For this reason, attempts have been made to use gametophytes obtained by culture as artificial seedlings. In this case, gametophytes are attached and grown on aquaculture ropes, and then cultured in containers such as flasks up to 2 L or in aquariums until the emerging young sporophytes reach leaf lengths of approximately 2–3 cm. Because the appressorium of the young sporophytes is underdeveloped, this culture is usually carried out statically or under very slow water flow to prevent the young sporophytes from falling off. After confirming the development of the appressorium, the sporophytes are transferred to culture under water flow to allow for larger growth. This is because water flow is essential for the sporophytes to come into contact with fresh medium for large growth. If static culture is continued, it is difficult to obtain large, streamlined sporophytes. Water flow can be generated by shaking or aeration in flasks or other containers. In aquariums, it is generated by a submersible pump.

[0006] Various studies have been conducted on the growth of wakame seaweed in tanks. For example, Patent Document 1 discloses a seaweed cultivation device equipped with a cylindrical tank with an opening at the top, an aeration mechanism, a water injection mechanism, a drainage mechanism, and a water flow adjustment mechanism for adjusting the water flow in the tank, and the water flow adjustment mechanism is made up of a cylindrical member with a roughly truncated cone shape having openings at the top and bottom, and the cylindrical member has its cone-shaped top opening located at the bottom of the cylindrical tank, its cone-shaped bottom opening located on the top opening side of the cylindrical tank, and its cone-shaped central axis coinciding with the central axis of the cylindrical tank. The cylindrical member has a plurality of openings in the vertical direction on its outer surface, the water injection mechanism has its water inlet near the inner peripheral edge of the cylindrical tank and the water injection direction is arranged in a direction approximately tangential to the cylindrical cross section, the aeration mechanism is arranged near the outer periphery of the water flow adjustment mechanism in the lower part of the cylindrical tank, and the drainage mechanism has its water intake located inside the water flow adjustment mechanism at the bottom of the cylindrical tank.

[0007] Non-patent document 1 describes that it was possible to obtain mature algal bodies from zoospores in flasks for the Laminariales plant, Undaria pinnatifida. More specifically, it describes that zoospores can be allowed to mature in a 2-liter flask in just over three months, that the morphology of each part of the algal body can be changed and maturation can be controlled by changing the photoperiod, and that such a culture method allows for the production of seedlings indoors without having to consider the timing, and that it can be easily used for breeding and genetic experiments.

[0008] Non-patent document 2 describes the effects of water temperature and water flow on the growth of cultivated wakame sporophytes, stating that the growth response to water flow differs depending on the developmental stage, with young sporophytes measuring 15.5 cm in total length growing well at 10 and 20 cm / s, and that in experiments on water temperature, high growth rates were observed at 11 to 17°C, and growth dropped significantly above 17°C, with the upper limit of the death temperature being 27°C, and that the growth rate near the upper limit of the optimum temperature for growth was higher at high flow rates (approximately 40 cm / s) than at low flow rates (approximately 5 cm / s). [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-36596 [Non-patent literature]

[0010] [Non-Patent Document 1] Notoya et al., "Life history and morphogenesis of the larvae in indoor culture", Monthly Marine, 1995, 27(1), pp.47-52, [Non-patent document 2] Baba et al., "Growth response of wakame seaweed to water temperature and water flow in a flow-through tank," Marine Biological Science Research Bulletin, 2006, No. 9, pp. 55-64 Summary of the Invention [Problem to be solved by the invention]

[0011] To efficiently develop useful wakame strains, it is necessary to shorten the long wakame life cycle, typically one year, and evaluate the traits of the next and subsequent generations at an earlier stage. Furthermore, wakame typically has large leaves, typically over one meter long, at the stage where it forms its reproductive organs, the sporophyll. Unlike edible use, developing useful strains requires only trait evaluation, and does not require the growth of large algal bodies. Conventional techniques rely on the growth of young sporophytes into large adults. Therefore, even though the goal is to develop useful strains, testing requires large aquaria to accommodate the growth of the algal bodies, and in some cases, in actual ocean waters. This leaves room for improvement in terms of convenience and cost.

[0012] For example, the technology described in Patent Document 1 requires large-scale facilities and a long cultivation period to grow algae to 1.5 to 2 meters. Patent Document 1 does not focus on strain selection or life cycle control. While the technology described in Non-Patent Document 1 allows the life cycle to be completed in a laboratory, large-scale facilities are required because sporophyte maturation occurs after the plant reaches a leaf length of 50 cm or more. Non-Patent Document 1 also only confirms the maturation of the sporophyte, not the maturation of the next-generation gametophyte. Non-Patent Document 1 does not focus on the growth conditions and growth period of young sporophytes. Non-Patent Document 2 describes that increased water flow can suppress growth retardation in sporophytes with a leaf length of 15.5 cm, even in high-temperature environments, but does not focus on the growth conditions and growth period of young sporophytes.

[0013] One aspect of the present invention aims to solve the above-mentioned problems by providing wakame algae and a method for cultivating the same, which shortens the life cycle when cultivating wakame and thereby facilitates the production of useful wakame strains. [Means for solving the problem]

[0014] The gist of the present invention is as follows. [1] A wakame alga having a leaf length of 8 cm to 20 cm and having sporophylls. [2] A method for cultivating the wakame algae body according to claim 1, a first step of inducing maturation and fertilization of the female and male gametophytes of wakame seaweed at a temperature of 8°C to 16°C to obtain sporophytes; a second step of culturing the sporulating bodies in a culture medium at 8°C to 16°C while flowing the culture medium until the sporulating bodies reach a leaf length of 0.5 cm to 2 cm; or for 40 to 70 days from the start of culturing the sporulating bodies; or until both of these conditions are met, thereby obtaining young sporulating bodies; and a third step of culturing the young sporophytes in a culture medium at 18°C ​​to 22°C while flowing the medium to obtain Undaria pinnatifida cells having a leaf length of 8 cm to 20 cm and sporophylls; A method for cultivating wakame algae, comprising: [3] 3. The method for cultivating wakame algae according to item 2, wherein the first step is performed by static culture, the second step is performed by shaking culture, and the third step is performed by aerobic culture. [Effects of the Invention]

[0015] According to one aspect of the present invention, it is possible to provide wakame algae and a cultivation method thereof that enable shortening of the life cycle when culturing wakame and thereby promoting the production of useful wakame strains. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a diagram illustrating gametophyte maturation. [Figure 2] FIG. 1 is a diagram illustrating the young sporophyte. [Figure 3] 1 is a diagram showing Undaria pinnatifida algae bodies according to Example 1. FIG. [Figure 4] FIG. 1 is a diagram showing Undaria pinnatifida algae bodies according to Comparative Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, an exemplary embodiment of the present invention (sometimes referred to as the present embodiment in this disclosure) will be described, but the present invention is not limited to the following embodiment.

[0018] One aspect of the present invention provides a wakame alga having a leaf length of 8 cm to 20 cm and having sporophylls. In this disclosure, "leaf length" refers to the distance from one end of the algal body (tip of the root) along the stem or center line to the other end (tip of the leaf), and is measured with a ruler (length measuring device). More specific measurement procedures will be described later in the "Examples" section. Leaf length is measured for each algal body. Therefore, it is sufficient that there is at least one algal body with a leaf length of 8 cm or more and 20 cm or less and with sporophyll. Whether or not a wakame alga has "sporophylls" can be distinguished by visual observation.

[0019] Another aspect of the present invention provides a method for cultivating Wakame algae of this embodiment. In one aspect, the method includes a first step of inducing maturation and fertilization of female and male gametophytes to obtain sporophytes; a second step of culturing the sporophytes until a leaf length of 0.5 cm to 2 cm is reached; or until 40 to 70 days have elapsed since the start of sporophyte culture; or until both of these conditions are met to obtain young sporophytes; and a third step of culturing the young sporophytes to obtain Wakame algae having a leaf length of 8 cm to 20 cm and sporophytes. In one aspect, the first step is carried out at 8°C to 16°C. In one aspect, the culture in the second step is carried out in a culture medium at 8°C to 16°C while the culture medium is flowing. In one aspect, the culture in the third step is carried out in a culture medium at 18°C ​​to 22°C while the culture medium is flowing. "Sporophyte" refers to the stage from the emergence of the sporophyte until it grows to a size that can be seen with the naked eye, and "young sporophyte" refers to the stage from the growth that can be seen with the naked eye until it reaches a leaf length of less than 8 cm.

[0020] The wakame (Undaria pinnatifida) life cycle, consisting of gametophyte development → gametophyte growth → gametophyte maturation → fertilization → sporophyte development → sporophyte growth → sporophyte maturation → zoospore release, is usually completed in one year. According to the wakame algae and cultivation method thereof of this embodiment, this life cycle can be shortened to, for example, about four to six months. This shortened life cycle can facilitate the production of useful wakame strains. In typical wakame cultivation, in order to obtain a large amount of edible parts, it is desirable to grow the sporophyte large (for example, to 1 m or more) and then allow it to mature. On the other hand, in the production of useful strains, the size of the algae is not important, as it is sufficient for the sporophyte to release zoospores. The wakame algae provided by this embodiment is a sporophyte that has sporophylls despite its small size. Such sporophytes are advantageous in terms of shortening the life cycle because they do not require a long period of time to grow.

[0021] Small sporophytes with sporophylls can be achieved by promoting sporophyte maturation. The present inventors conducted various studies to determine the conditions under which sporophyte maturation can be promoted. As a result, they found that maturation is promoted by exposing sporophytes to a high-temperature environment before they reach a large growth stage. Without being bound by theory, it is speculated that when sporophytes are exposed to a stressful environment, such as a high temperature that is inherently unsuitable for sporophyte growth, sporophyll formation for the next generation takes priority over increasing the size of the algae. For example, the aforementioned Non-Patent Document 2 describes that growth retardation in sporophytes exposed to a high-temperature environment can be reduced by increasing water flow, but does not focus on the relationship between sporophyte maturation and growth conditions. By the time the sporophyte matures and forms sporophylls, the leaf length is typically large, for example, 1 m or more. However, the wakame algae of this embodiment is small, measuring between 8 cm and 20 cm. Such wakame algae is previously unknown and unique.

[0022] The varieties of the wakame algae of this embodiment or the female and male gametophytes of the wakame used for cultivating the same are not particularly limited. The female and male gametophytes may be derived from zoospores collected from a naturally growing strain that has formed sporophytes. In one aspect, naturally growing strains collected from a variety or region known to have a suitable growth temperature for sporophytes of less than 18°C ​​may be used.

[0023] An exemplary embodiment of the method for cultivating wakame algae bodies according to this embodiment will be described below.

[0024] (first step) In this step, maturation (i.e., formation of archegonia and antheridia) and fertilization of the female and male gametophytes of wakame are induced at temperatures between 8°C and 16°C to obtain sporophytes. In one embodiment, the female and male gametophytes are maintained in culture, and then maturation is induced at temperatures between 8°C and 16°C. The culture after maintenance culture and maturation induction may be static culture. The medium for maintenance culture may be, for example, a seawater medium. In one embodiment, the seawater medium is natural seawater or artificially synthesized seawater to which a nutrient-enriched medium (e.g., Provasoli Enriched Seawater) has been added, or it is an artificial seawater medium enriched with nutrients. During maintenance culture, gametophyte maturation may be suppressed by, for example, eliminating the presence of iron in the medium, irradiating it with blue light, or maintaining a low culture temperature (e.g., 4°C or below). Maturation induction may be performed at a desired timing depending on the schedule for seedling production, experiments, etc. Maturation induction may be achieved by one or more of the following means: adding iron to the medium, changing from blue light irradiation to white light irradiation, increasing the culture temperature, etc. When maturation is induced by adding iron, one or more of ferrous ammonium sulfate, ferric chloride, etc. may be added to the medium as an iron source. The iron concentration in the medium may be 10 mg / L or more and 50 mg / L or less.

[0025] The temperature range suitable for maturation and fertilization of wakame gametophytes is generally between 8°C and 16°C. After maturation induction, the temperature is typically maintained continuously between 8°C and 16°C, although periods within the range of 8°C and 16°C may be interrupted by periods outside the range.

[0026] After maturation induction, archegonia formation occurs in the female gametophyte and antheridia formation occurs in the male gametophyte, usually within several weeks. In one embodiment, the absence of archegonia or antheridia formation before maturation induction and the formation of archegonia or antheridia after maturation induction are confirmed by observation under an optical microscope. Fertilization of the egg and sperm, followed by germination, produces sporangia. The generation of sporangia can be confirmed by an optical microscope. In one embodiment, sporangia are obtained approximately one month after maturation induction.

[0027] (Second process) In this step, the sporelings are cultured in a culture medium at 8°C to 16°C with the medium flowing for a period until the following conditions are met: the sporelings reach a leaf length of 0.5 cm to 2 cm; or 40 to 70 days from the start of sporeling culture; or both. The temperature range of 8°C to 16°C is generally suitable for the growth of wakame sporelings. The culture temperature is typically maintained continuously at 8°C to 16°C, although periods within the 8°C to 16°C range may be temporarily interrupted by periods outside the 8°C to 16°C range. The composition of the culture medium used in the second step may be the same as that used to culture gametophytes, but it is preferable to add iron.

[0028] The photoperiod in the second step is preferably a long-day condition from the viewpoint of shortening the life cycle by promoting growth, and in one embodiment may be a 14-hour light, 10-hour dark period (14L10D) cycle. From the viewpoint of photosynthetic efficiency due to chlorophyll a and fucoxanthin, which are photosynthetic pigments contained in wakame, the light wavelength should be visible light, 360 nm or more, and preferably contains wavelengths of 400 nm or more and 700 nm or less. The light intensity is preferably 50 μmol / m from the viewpoint of promoting growth. 2 / s or more, and from the viewpoint of the photosynthetic pigments contained in wakame, it is preferably 200 μmol / m 2 The light source may be, for example, an optical semiconductor element such as a light emitting diode (LED) or a laser diode (LD), or an organic or inorganic electroluminescence (EL).

[0029] In the second step, the sporophytes may be attached to a carrier via appressoria or may float freely in the culture solution. Examples of carriers include natural stone, artificial stone, concrete blocks, Cremona rope or thread, and polyvinyl chloride pipes wrapped around these materials. While static or gentle water flow is advantageous for appressorial development, appressorial development is not essential in this embodiment. According to the inventors' studies, when sporophytes are aerated in the laboratory without being attached to a carrier, they grow large without appressorial development. Furthermore, in this case, if the sporophytes are forced into contact with the carrier, for example by clamping them between ropes, appressorial development begins. In other words, appressorial development is not considered essential for sporophyte growth and maturation. Therefore, in the second step, even sporophytes or young sporophytes are placed under water flow to promote growth, thereby shortening their life cycle. However, sporophytes or young sporophytes floating freely in the culture solution tend to have lower yields than those attached to a carrier because some of them may be washed away when the culture solution is changed.

[0030] In the second step, the means for generating a flow of the culture medium may be shaking culture, etc. Shaking culture can be performed by placing spores in a glass or plastic container such as an Erlenmeyer flask or a deep Petri dish, placing the container in a shaker, and gently moving the container horizontally in a right-and-left reciprocating motion or in a figure-eight pattern. Shaking culture can provide a gentler flow of the culture medium compared to, for example, aerobic culture, which will be described later in the third step. While aerobic culture can also be used in the second step, shaking culture is preferred in the second step because it is less likely to result in loss of spores due to the violent flow of the culture medium and provides a good yield.

[0031] The following method is used to confirm whether the leaf length has reached 0.5 cm or more and 2 cm or less. Five or more individuals are randomly selected from the culture medium. Of these, those that are judged to be growing normally based on the morphology of the algal bodies are used as the measurement targets. If there are fewer than five individuals to be measured, the individuals are selected again. The leaf lengths of the five or more measurement targets obtained are measured. The first time when the leaf length of the majority of the measurement targets (for example, three or more if there are five measurement targets) is 0.5 cm or more and 2 cm or less is considered to be the time when the leaf length has reached 0.5 cm or more and 2 cm or less. In one embodiment, five individuals can be measured. Leaf length measurements may be carried out every week.

[0032] (Third step) In this step, young sporophytes are cultured in a culture medium at 18°C ​​to 22°C while the medium is flowing to obtain wakame algae having sporophytes and a leaf length of 8 cm to 20 cm. The culture temperature is typically maintained continuously at 18°C ​​to 22°C, although periods within the 18°C ​​to 22°C range may be temporarily interrupted by periods outside the 18°C ​​to 22°C range. The composition of the culture medium used in the third step may be the same as that described above for the second step.

[0033] In wakame, the solution temperature suitable for sporophyte growth is typically around 8°C to 16°C, and growth tends to slow when the water temperature exceeds 20°C due to seasonal changes. Conventional techniques typically do not employ growth conditions that expose young sporophytes to high temperatures of 18°C ​​to 22°C or lower. In this embodiment, the sporophytes only need to fulfill the biological requirements for maturation; enlargement of the algal bodies is not required. Sporophyte maturation can be induced by seasonal changes in water temperature and photoperiod. In this embodiment, young sporophytes are exposed to high-temperature stress in a culture solution of 18°C ​​to 22°C or lower, thereby slowing their growth and promoting maturation. Because young sporophyte growth can become difficult when the culture solution temperature exceeds 22°C, it is desirable to set the upper limit to 22°C or lower.

[0034] In the third step, the flow of the culture medium may be generated by air circulation through aeration culture, water flow caused by a propeller, or the like. Aeration culture can be performed, for example, as follows: The culture medium and young sporophytes are placed in a container such as a plastic bottle. The amount of culture medium is not limited, but in one embodiment, it may be 0.3 L to 10 L, or 1 L to 3 L. An aeration tube made of ceramic, glass, plastic, or the like connected to an air pump may be placed inside the bottle to generate a water flow caused by air within the container. This can generate a water flow that is stronger than, for example, the shaking culture described above in the second step. In the third step, the young sporophytes are exposed to high-temperature stress, but a certain degree of growth is possible by vigorously flowing the culture medium. In the third step, a vigorous water flow may be applied as long as the young sporophytes can remain in the container.

[0035] The sporophyte that has undergone the third step can have sporophylls despite its small size, with a leaf length of 8 cm to 20 cm. The period from the start of gametophyte induction to the formation of sporophylls can be preferably 180 days or less, or 150 days or less. A shorter period is advantageous, but in a typical embodiment, it can be 120 days or more. In conventional culture, the period generally requires 300 days or more, so this embodiment contributes to a significant shortening of the life cycle. According to this embodiment, the entire life cycle can be shortened from the conventional approximately one year to, for example, about 4 to 6 months. [Example]

[0036] The following examples further illustrate exemplary embodiments of the present invention, but the present invention is not limited to these examples.

[0037] <Materials used> [Wakame female and male gametophytes] Gametophytes (female and male gametophytes) obtained by isolating zoospores from the wild-caught wakame (Undaria pinnatifida) collected in the sea off Muroran, Hokkaido, were used.

[0038] [Culture solution] Throughout the experiments, the culture medium used was seawater that had been filtered or autoclaved and supplemented with 0.5% of the nutrient-enriched medium with the following composition: (PESI medium) H2O total 100ml NaNO 3350mg Disodium glycerophosphate 50mg 25ml of the following PII metal mixture Fe (as EDTA 1:1) 2.5mg Iodine (K + as) 0.1mg Tris 500mg pH 7.8~8.0 (PII metal mixture) H2O total 100ml Na2-EDTA 100mg Fe(Cl - as) 1mg B (as H3BO3) 20mg Mn(Cl - as) 4mg Zn(Cl - as) 500μg Co(Cl - as) 100μg

[0039] <Culture test> [Example 1] (maintenance culture) The female and male gametophytes were inoculated into a 10 cm diameter petri dish containing 20 mL of culture solution and maintained at 15°C for 30 days under static culture conditions. 2 / s or less.

[0040] (first step) To induce gametophyte maturation, 20 mL of medium containing 30 mg / L of iron was added to the above dish. Static culture was performed at 15°C under a photoperiod of 14L / 10D. Light irradiation was performed using an LED light source with a light intensity of 50 μmol / m 2The incubation was carried out at 1000 rpm for 1 minute. The formation of sporulation bodies was confirmed every week. 15 days after maturation induction (i.e., addition of an iron source), the formation of antheridia was observed, and 20 days after maturation induction, the release of eggs was observed (Figure 1). This confirmed the maturation of gametophytes. 32 days after maturation induction, the presence of sporulation bodies was confirmed.

[0041] (Second process) Spores were removed from the culture medium using a pipette and placed in a 300 mL glass Erlenmeyer flask containing 100 mL of culture medium. Shaking culture was performed at 15°C under a 14L / 10D photoperiod. The shaker was operated at 100 rpm. 48 days after the start of maturation induction (16 days after the start of culture in the second step), spores were randomly removed from the Erlenmeyer flask and placed on a flat surface, and their leaf lengths were measured (Figure 2). Of the 15 individuals shown in Figure 2, five were selected based on their morphology and were judged to be growing normally. Of the five spores observed, three (i.e., the majority) were confirmed to have leaf lengths between 0.5 cm and 2 cm. Individuals with leaf lengths between 0.5 cm and 2 cm were collected as young spores.

[0042] (Third step) The young sporophytes were placed in a 2-liter plastic cylindrical container containing 1.5 liters of culture medium. An aeration tube was installed inside the container, and a strong current was generated by an air pump to prevent the culture medium from overflowing. Culture was performed at 20°C under a 14-hour, 10-day photoperiod. The presence or absence of sporophyte formation was confirmed by visual observation every week. 131 days after the start of maturation induction, four of the four sporophytes observed (i.e., the majority) were confirmed to have sporophytes (Figure 3). These four sporophytes were selected from the five sporophytes shown in Figure 3, which were judged to be growing normally based on their morphology. The leaf lengths of the sporophytes with sporophytes ranged from 8 cm to 20 cm (a: 8.1 cm, b: 11.0 cm, c: 13.7 cm, d: 13.4 cm, respectively), with a numerical average of 11.6 cm. The aerated culture was continued without changing the culture conditions, and visual observation was carried out every week to check for the formation of uniscoria and the release of zoospores in the sporophytes. 180 days after the start of maturation induction, it was confirmed that two of the three sporophytes with sporophylls had formed uniscoria and released zoospores. Leaf length was measured using the following procedure. For each individual, the length of the path from one end of the algal body (tip of the root) along the stalk or center line to the other end (tip of the leaf) was measured with a ruler. Specifically, from the appressorium side toward the tip of the leaf, the linear length of the appressorium, the linear length of the stalk, and the linear length of the center line of the leaf were measured in turn with a ruler, and these were summed to obtain the leaf length.

[0043] <Comparative Example 1> (Maintenance culture and first step) The procedure was the same as in Example 1. 30 days after the start of maturation induction, the presence of spore bodies was confirmed. (Second step of comparison) Static culture was continued at 15°C without changing the culture conditions from the first step, and 100 days after the start of maturation induction, it was confirmed that of the five sporophytes observed, three had leaf lengths of 1.5 cm or more. Culture was continued further, and 120 days after the start of maturation induction, the leaf lengths of the three sporophytes were measured. However, the leaf lengths of the individuals that had been 1.5 cm or more were all less than 8 cm (specifically, 2.3 cm, 2.5 cm, and 2.0 cm), with a number average of 2.3 cm, and they had not grown larger. Furthermore, the shape of the algal bodies was shrunken and not a clean, streamlined form.

[0044] <Comparative Example 2> (Maintenance culture and first step) The procedure was the same as in Example 1. 30 days after the start of maturation induction, the presence of spore bodies was confirmed.

[0045] (Second process) The same procedure as in Example 1 was used. 48 days after the start of maturation induction, it was confirmed that of the five sporophytes observed, three (i.e., the majority) had leaf lengths of 0.5 cm to 1 cm (thus falling within the range of 0.5 cm to 2 cm). Individuals with leaf lengths of 0.5 cm to 1 cm were collected as young sporophytes.

[0046] (Third step of comparison) The young sporophytes were cultured using the same procedure as in Example 1, except that the temperature was changed from 20°C to 15°C. 130 days after the start of maturation induction, four of the six sporophytes observed were confirmed to have grown to leaf lengths of 7 cm or more (Figure 4). These six individuals were selected from the nine individuals shown in Figure 4 that were judged to have grown normally based on the morphology of the algal bodies. Specifically, leaf length a = 4.8 cm, leaf length b = 7.6 cm, leaf length c = 10.3 cm, leaf length d = 9.5 cm, leaf length e = 7.8 cm, and leaf length f = 5.0 cm. Four of the six individuals had leaf lengths of 7 cm or more. At this point, no sporophytes with sporophylls were observed. Culture was continued, and 180 days after the start of maturation induction, all of the individuals that had grown to leaf lengths of 7 cm or more had leaf lengths of 15 cm or more. However, no sporophytes with sporophylls were observed. The results are summarized in Table 1.

[0047] [Table 1]

Claims

1. A wakame alga having a leaf length of 8 cm or more and 20 cm or less and having sporophylls.

2. A method for cultivating the wakame algae body according to claim 1, a first step of inducing maturation and fertilization of the female gametophyte and male gametophyte of wakame at a temperature of 8°C to 16°C to obtain sporophytes; a second step of culturing the sporulating bodies in a culture medium at 8°C to 16°C while flowing the culture medium until the sporulating bodies reach a leaf length of 0.5 cm to 2 cm; or for 40 to 70 days from the start of culturing the sporulating bodies; or until both of these conditions are met, thereby obtaining young sporulating bodies; and a third step of culturing the young sporophytes in a culture medium at 18°C ​​to 22°C while flowing the culture medium to obtain Undaria pinnatifida algae having a leaf length of 8 cm to 20 cm and sporophylls; A method for cultivating wakame algae, comprising:

3. 3. The method for cultivating wakame algae according to claim 2, wherein the first step is performed by static culture, the second step is performed by shaking culture, and the third step is performed by aerobic culture.

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