Brassica rapa (PROSEA)

Plant Resources of South-East Asia Introduction

List of species

Brassica rapa L.

Protologue: Sp. pl.: 666 (1753).

Family: Cruciferae

Chromosome number: 2n= 20

Major taxa and synonyms

• Cv. group Caisin - see separate article.

• Cv. group Chinese Cabbage - see separate article.

• Cv. group Mizuna: Toxopeus, Yamagishi & Oost in Cruc. Newsl. 12: 5 (1987). Synonyms: B. japonica Makino (1912) non (Thunb.) Sieb. (1865/66), B. campestris L. ssp. nipposinica (Bailey) Olssen (1954), B. rapa L. ssp. nipposinica (Bailey) Hanelt (1986).

• Cv. group Neep Greens: Toxopeus, Oost, Yamagishi & Prescott-Allen in Cruc. Newsl. 13: 9 (1988). Synonym: B. perviridis (Bailey) Bailey (1940) for certain forms (komatsuna).

• Cv. group Pak Choi - see separate article.

• Cv. group Taatsai: Toxopeus, Yamagishi & Oost in Cruc. Newsl. 12: 5 (1987). Synonyms: B. narinosa Bailey (1922), B. campestris L. ssp. narinosa (Bailey) Olssen (1954), B. rapa L. ssp. narinosa (Bailey) Hanelt (1986).

• Cv. group Vegetable Turnip: Toxopeus, Oost & Reuling in Cruc. Newsl. 9: 58 (1984). Synonyms: B. campestris L. ssp. rapa (L.) Hook.f. & Anders. (1875), B. campestris L. ssp. rapifera (Metzger) Sinsk. (1928), B. rapa L. ssp. rapa sensu auct. mult.

Vernacular names

General: neep crops (En).

• Cv. group Mizuna: mizuna, mibuna, kyona (Jap/En).

• Cv. group Neep Greens: komatsuna, kabuna, turnip greens (Jap/En).

• Cv. group Taatsai: taatsai (Chin/En).

• Cv. group Vegetable Turnip: vegetable turnip (En). Rave, navet (Fr).

Origin and geographic distribution

The origin of B. rapa is not known. The wide variation of neep crops evolved in different parts of the Eurasian continent. Besides Chinese cabbage, pak choi and caisin the leafy vegetable types (leaf neeps) comprise cv. groups Mizuna, Neep Greens and Taatsai, developed in temperate regions of Asia. The many forms of vegetable turnip are highly regarded in Japan as well as in Europe where also fodder turnip used to be a very popular crop (root neeps). Oilseed types (seed neeps), grown for rape oil, are important in India and Canada.

The turnip is the oldest B. rapa crop on record. It was described in ancient Greek times of Alexander the Great, whose empire included the Middle East and Persia, from where it must have found its way to East Asia. Quite independently of each other in Europe and in Japan a well-defined, polymorphic group of vegetable turnips had been created by the 18th Century.

Uses

All products, the foliage of the leaf neeps as well as the root of vegetable turnip, are fresh vegetables, consumed boiled or fresh in salads or fried in special dishes.

Production and international trade

The cv. groups Mizuna, Neep Greens and Taatsai are most important in mainland China and in Japan. Cv. group Vegetable Turnip is most important in Japan. In South-East Asia they are occasionally cultivated in highland areas for a foreign clientele.

Properties

Per 100 g edible portion the approximate composition of leaves is: water 90 g, protein 3 g, fat 0.4 g, carbohydrates 5 g, fibre 0-4 g, ß-carotene 4.6 mg, vitamin C 139 mg. The energy value is 118 kJ/100 g.

The roots contain per 100 g edible portion: water 90 g, protein 1 g, trace of fat, carbohydrates 8 g, fibre 0.7 g, trace of ß-carotene, vitamin C 25 mg. The energy value is 143 kJ/100 g.

Description

• Annual or biennial herb with stout taproot, often fusiform to tuberous (turnips).
• Stem erect, branched, up to 1.5 m tall.
• Leaves very variable, depending on cultivar, growing in a rosette during the vegetative stage; basal leaves more or less petioled, bright green, lyrate-pinnatipartite, dentate, crenate or sinuate with large terminal lobe and up to 5 pairs of rather small lateral lobes; lower cauline leaves sessile, clasping, pinnatifid; upper cauline leaves sessile, clasping, undivided, glaucous, entire to dentate.
• Inflorescence a loosely corymbiform raceme with open flowers overtopping the buds; pedicel 1-3 cm long; sepals yellow-green; petals yellow, clawed, 6-11 mm long; stamens 6, tetradynamous.
• Fruit a silique, linear, 4-10 cm × 0.2-0.4 cm, beak 0.5-3 cm long, seeds 20-30.
• Seed globose, 1-1.5 mm in diameter, dark brown with a fine distinct reticulum.

• Cv. group Mizuna consists of spontaneously tillering plants with pinnate leaves (mizuna cultivars) or entire leaves (mibuna cultivars).

• Cv. group Neep Greens comprises essentially non-heading plants, including crops such as komatsuna, zairainatane, kabuna, turnip greens.

• Cv. group Taatsai typically grows a flat rosette of many small dark green leaves.

• Cv. group Vegetable Turnip consists of forms of which the storage organ (swollen hypocotyl and root), i.e. the turnip, is used as vegetable; the leaves may be used as a vegetable as well. Turnips vary widely in shape, from flat through globose to ellipsoid and cylindrical, blunt or sharply pointed, flesh white, pink or yellow, apex white, green, red, pink or bronze. All these characteristics may occur in cultivars in any imaginable combination.

Growth and development

In general these are fast-growing crops, harvestable 6-15 weeks after sowing, depending on type and season. Biennial types bolt after a period of relatively low temperatures. In the tropics these crops are only suitable for cultivation at higher altitudes (above 800 m).

Other botanical information

In the literature, the taxonomy of B. rapa is confused. Often the name B. campestris L. is used for this species, but B. rapa was recently proven to be the correct name. In most floras B. rapa is roughly divided into 2 subspecies: ssp. rapa for the plants with swollen roots, cultivated for vegetable and for fodder; and ssp. campestris (L.) Clapham (syn.: ssp. oleifera DC.) for the plants mainly cultivated for the oil of its seeds. Many infraspecific classifications have been proposed, each trying to capture the wide variation of the cultivated forms in a taxonomic system, the result always being unsatisfactory. A classification system according to the code for the nomenclature of cultivated plants is followed here. It arranges cultivars into cultivar groups; it seems more promising but is still being tested.

Ecology

The four cv. groups described require the lower temperatures of tropical highlands and are well adapted to long-day conditions. They have a high water requirement. Most cultivars of vegetable turnip require a degree of cold induction for flowering which will not be met in tropical highlands below 2000 m.

Agronomy

Plants should be grown on well-watered, raised beds of light, well-manured soil either by direct sowing or with transplants raised in a densely sown seed-bed. They are very responsive to N fertilizers. In the first few weeks of growth, clean weeding should be practised. The limited cultivation experience with these crops in tropical highlands makes it difficult to discuss diseases and pests. The use of healthy seed is of major importance. At all costs clubroot disease (Plasmodiophora brassicae) should be kept out of any Brassica crop. The disease is often introduced in the soil on roots of transplants from other infested areas. It can spread rapidly with irrigation water and once the disease is established it can only be controlled by growing non-host (non-Brassica) crops for 5 or more years.

Yields will vary widely according to the type and life cycle of the crop concerned, 30-50 t/ha of fresh product being the range for well-managed crops. The produce should reach markets on the second day after harvesting at the latest. A good infrastructure is essential.

Genetic resources and breeding

Major germplasm collections are present in gene banks in Japan, the United Kingdom and the United States. No breeding work is going on in any of the cv. groups described beyond maintaining existing cultivars marketed by the major international Japanese and European seed firms. B. rapa consists of a range of diverse crops all of which are completely cross-compatible and characters may be recombined at will using conventional seed breeding principles.

Prospects

In South-East Asia, the neep crops described will be of interest to non-traditional middle and higher income groups in the larger cities who may be prepared to pay extra for the new crop products. The crops will add to the existing variety. Several crops have been introduced on a trial basis in recent years by European/Japanese/Korean seed firms. B. rapa as a whole offers wide prospects for the development of new vegetables adapted to specific ecological conditions and market preferences.

Literature

• Jonsell, B., 1982. Brassica. In: Polhill, R.M. (Editor): Flora of tropical East Africa. Cruciferae. A.A. Balkema, Rotterdam, the Netherlands. pp. 3-7.
• Mansfeld, R., 1986. Verzeichnis landwirtschaftlicher und gärtnerischer Kulturpflanzen (ohne Zierpflanzen) [Register of agricultural and horticultural plants in cultivation (without ornamentals)]. Schultze-Motel, J. et al., editors 2nd edition. Springer Verlag, Berlin, Germany. Vol. 1. pp. 300-306.
• Oost, E.H., Brandenburg, W.A., Reuling, G.T.M. & Jarvis, C.E., 1987. Lectotypification of Brassica rapa L., B. campestris L. and neotypification of B. chinensis L. (Cruciferae). Taxon 36(3): 625-634.
• Shinohara, S. (Editor), 1984. Vegetable seed production technology of Japan. Shinohara's Authorized Agricultural Consulting Engineer Office, Tokyo, Japan. Vol. 1. pp. 115-123, 239-268.
• Toxopeus, H., Oost, E.H., Yamagishi, H. & Prescott-Allen, R., 1988. Cultivar group classification of Brassica rapa L.: update 1988. Cruciferae Newsletter No 13: 9-11.

Authors

• H. Toxopeus

• See also the genus page
• See Brassica (PROSEA Oils and fats) for the oil use.