Undaria Cultivation

The brown algal genus Undaria (another species of 'kelp') is an important food delicacy in Japan and Korea (tradi tionally known as 'wakame'). It is sold boiled or dried and is especially appreciated as an ingredient for soybean paste soup ('misoshiru') and seaweed salad. Undaria has three species (Undaria pinnatifida [Harvey] Suringar, Undaria undarioides [Yendo] Okamura, and Undaria peter oseniana [Kjellman] Okamura), and of these, U. pinnatifida is the most important. The production of Undaria has tremendously increased, since its cultivation started in China, by 2000. According to the FAO data, 2 519905 mt (wet weight), valued at more than 1.0 billion USD, of

Porous fertilizer jar Bamboo tube

Porous fertilizer cylinder

Young sporophytes

Rope Anchor

Young sporophytes

Porous fertilizer cylinder

Rope Anchor

Figure 6 (a) Single-line bamboo rafts and (b) double-line bamboo rafts. (a-c) Bamboo rafts used for culture of Laminaria in China. (d) Long line with Laminaria after 8 months of growth in the Yellow Sea, China. (e) Long line with Laminaria in South Korea. (f) Young sporophytes growing on long line. (a-c) Modified from Cheng TH (1969) Production of kelp. A major aspect of China's exploitation of the sea. Economic Botany 23: 215-236. (e) Courtesy of E. Hwang.

Figure 6 (a) Single-line bamboo rafts and (b) double-line bamboo rafts. (a-c) Bamboo rafts used for culture of Laminaria in China. (d) Long line with Laminaria after 8 months of growth in the Yellow Sea, China. (e) Long line with Laminaria in South Korea. (f) Young sporophytes growing on long line. (a-c) Modified from Cheng TH (1969) Production of kelp. A major aspect of China's exploitation of the sea. Economic Botany 23: 215-236. (e) Courtesy of E. Hwang.

Undaria was produced globally through culture in 2004, with 2 196 070 mt coming from China alone. In nature, Undaria commonly grows in open seas or within bays on the temperate coasts of Japan, Korea, China, and other areas of the northwest Pacific which may have a rocky substrate. Usually, the frond grows to a length of 1-2 m.

The life cycle of Undaria consists of a microscopic game tophytic phase and a large macroscopic sporophytic phase and is essentially an annual species. Young fronds of Undaria appear late in October to early November and grow rapidly until early spring. The mature sporophytes release zoospores that germinate on rocky substrata and

Cable rope

Anchor (sand bag)

Side view

Top view

Side view

Culture rope Weight

Culture rope Weight

Vertical hanging, single line

Cable rope e

Horizontal hanging, single line

Hanging rope Culture rope

Horizontal hanging, bamboo raft

Figure 7 (a-c) Methods for Undaria cultivation. (d) Undaria spore collector. The frame is 50 cm x 50 cm and synthetic seed string is wound around the frame. (e) Open water cultivation of Undaria. (a-c) Modified from Akiyama K and Kurogi M (1982) Cultivation of Undaria pinnatifida (Harvey) Suringar, the decrease in crops from natural plants following crop increase from cultivation. Bulletin of the Tohoku Regional Fisheries Research Laboratory 44: 91-100. (e) Courtesy of E. Hwang.

Figure 7 (a-c) Methods for Undaria cultivation. (d) Undaria spore collector. The frame is 50 cm x 50 cm and synthetic seed string is wound around the frame. (e) Open water cultivation of Undaria. (a-c) Modified from Akiyama K and Kurogi M (1982) Cultivation of Undaria pinnatifida (Harvey) Suringar, the decrease in crops from natural plants following crop increase from cultivation. Bulletin of the Tohoku Regional Fisheries Research Laboratory 44: 91-100. (e) Courtesy of E. Hwang.

develop into male and female gametophytes. After ferti lization, the zygote develops into a sporophyte, thereby completing the life cycle. The cultivation of Undaria consists of four stages and is essentially identical to that of Laminaria (Figure 7). It consists of collection of zoos pores and seedlings, culture of gametophyte germlings, outgrowing of thalli, and the harvesting and processing of the thalli.

The mature sporophylls are first partially dehydrated to induce release of zoospores and are then placed in culture tanks filled with seawater. Another seeding pro cess called the 'free living technique' uses vegetative gametophytes grown in flasks and is similar to the Laminaria rearing technology of clonal gametophyte tech nology. The seeded twine (usually 50 m of seed string) wrapped frames (Figure 7d) are removed from the seed ing tank and arranged vertically in a temperature controlled culture tank about 1 m deep. During summer and early autumn, the zoospores develop into microscopic gametophytes on the seeding frames that are wrapped with the twine. The germlings are allowed to develop to seedlings (2-3 cm) before removal and out planting along the open coast. The out planting of nursery grown seed lings starts in autumn when water temperature is about 20 °C. The original seeding ropes, which initially had seed string inserted within the braided rope, are cut into lengths of 4-6 cm (with approximately 10 seedlings each) and inserted into the twist of the main cultivation rope. They are then set into the sea using rafts or long lines (Figures 7a-7c). Generally, Undaria reaches a harvestable size about 3-5 months after it is transferred to the sea when they reach a length of 0.5-1.0 m (Figure 7e). After the rope is hauled up from the sea on the boat, the cultivated thalli are cut from the rope with a sickle. Each harvested frond is approximately 5 kg in wet weight. The crop may be sold fresh, sun dried, or artificially dried.

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