Zizania latifolia (PROSEA)

Plant Resources of South-East Asia Introduction

List of species

Zizania latifolia (Griseb.) Turcz. ex Stapf

Protologue: Kew Bulletin 1909: 385-390 (1909).

Family: Gramineae

Chromosome number: 2n= 30, 34

• Limnochloa caduciflora Turcz. ex Trinius (1840),
• Hydropyrum latifolium Griseb. (1853),
• Zizania caduciflora (Trinius) Handel-Mazzetti (1936).

• Manchurian wild rice, Manchurian water rice (En)
• Riz sauvage de Mandchourie (Fr)
• Thailand: nomai-nam (Bangkok), kapek (southern)
• Vietnam: củ niễng, niêng niễng, lúa miêu.

Z. latifolia is indigenous in north-eastern India, Burma, China, Japan, and in parts of eastern Siberia and the Russian Far East. Primarily used as a cereal in ancient times, its evolution and cultivation as a stem vegetable in China dates back at least to the 10th Century. It is now rather widespread in cultivation in eastern and south-eastern Asia (China, Korea, Japan, Taiwan, Indo-China, Thailand, Burma, Malaysia). In Indonesia it is cultivated locally by Chinese people. It has been introduced in Europe, New Zealand, and North America as well.

Z. latifolia is cultivated for its swollen culm ("gau sun" in Cantonese), which is the result of hypertrophy caused by the smut fungus, Ustilago esculenta. It is probably the only product of a plant host and a fungal parasite eaten as a vegetable. Modes of preparation of the gall-like structure are similar to those for bamboo shoots. The firm, outer green layer is removed so that the softer, white inner portion remains. This is parboiled before further cooking or frying with meat and other vegetables, or canned in brine.

Grains of Z. latifolia have been used for food, sometimes in the form of flour. The culms, rhizomes and grains are prescribed during fevers for their cooling, diuretic, and thirst-relieving properties. The ash of the rhizomes mixed with white of egg is an ointment for burns. In Europe the plants have been used for forage and to make paper. In Japan the teliospores of the smut fungus, mixed with oil, are used to darken and thicken eyebrows and hair.

Manchurian wild rice is mainly grown on a small scale for domestic consumption and local markets. No production statistics are available.

The swollen, infected culms contain per 100 g edible portion: water 78.5 g, protein 1.7 g, carbohydrates 4.7 g, cellulose 1.6 g, ash 0.5 g, Ca 21 mg, P 80 mg, Fe 1.2 mg, vitamin C 2.0 mg. The energy value is 109 kJ/100 g.

• Aquatic perennial tillering grass with strongly developed rhizomes and stolons, up to 3 m long.
• Mature rhizome unbranched, prostrate and nodose, green; apex and nodes solid, internodes hollow and divided into chambers by transverse membranous septa; mean external diameter 2 cm.
• Culm firm, erect, glabrous, filled with spongy pith and partitioned in the lower part, initially enclosed by the leaves but becoming exposed as the lower leaves die; apex solid, 0.6 cm long, consisting of 1-3 internodes; remainder of the culm consisting of 3 or more hollow internodes, each about 6 cm long; each node of the mature culm may give rise to a lateral bud which will develop into a shoot.
• Leaf-sheath loose, ribbed, glabrous; ligule 2.5 cm, top rounded and bifid; leaf-blade firm, narrowly linear-lanceolate, 50-100 cm × 2-3 cm, long-acuminate, scaberulous on both sides with very rough margins; midrib stout.
• Inflorescence a panicle, 40-60 cm long, narrowly pyramidal; branches ascending, arranged in pseudowhorls, with a tuft of long white hairs in the axils; male spikelets on the lower part of the panicle, lanceolate, 8-12 mm long, usually purplish, acute or short-awned; stamens 6; female spikelets on the upper part, pale green, linear, 15-25 mm; lemma oblong, acuminate, very scabrid; awns erect, 2-3 mm long, scabrous.
• Caryopsis linear-oblongoid, 5 mm × 1 mm.

Under the stimulus of Ustilago esculenta (enhanced production of auxins and cytokinins), the apical 3 or 4 internodes of the immature culm swell to produce a conical to fusiform, succulent, rather compact, fleshy gall, 5-10 cm × 2-4 cm, which is used as a vegetable. It consists for the greater part of host tissue and a comparatively small amount of mycelium of the fungus. Parasitized plants do not flower. The fungus survives in the rhizome and culm. U. esculenta is not known in other host species; it is a hardy fungus withstanding 15 °C of frost. Flowering plants sometimes occur if produced on rhizomes not penetrated by the systemic mycelium.

Several cultivated forms are distinguished in East Asia mainly based on size, colour and texture of the galls.

The natural habitat of Z. latifolia includes borders of lakes, still-water bays and slow-running streams. It seems tolerant of a wide range of climatic and soil conditions.

Z. latifolia is propagated vegetatively by planting rhizome parts with 1-3 stalks or by cuttings of immature culms consisting of 3-6 internodes. The smut fungus is usually present in these planting materials. The field should be flooded with a layer of water approximately 10-20 cm deep. Land preparation is very similar to that of rice fields. Organic fertilizer should be incorporated in the soil. On account of the strong tillering, Z. latifolia is planted at moderate densities ranging from 10 000-30 000/ha. Additional applications of fertilizer are carried out at intervals of about one month.

The major pests of Manchurian wild rice are similar to those of ordinary rice (Oryza sativa L.): the green leaf hopper (Nephotettix bipunctatus), the brown plant hopper (Nilaparvata lugens), paddy army worm (Mythimna separata) and paddy swarming caterpillar (Spodoptera mauritia).

Galls start to appear about 4-5 months after planting and are ready for harvest 1-2 weeks later. Subsequent harvests can be made at intervals of 1-2 weeks. Per tuft about 20-30 galls can be harvested per season. Galls are sized 5-10 cm × 2-4 cm, and weigh approximately 25-65 g. Harvesting is done manually and the galls are tied together by the leaf-sheath portion for transport to the market . The inner white core is also sold in cans and fresh-frozen in East Asia. The leaves can be harvested year-round for forage.

There are no known germplasm collections or breeding programmes. Near relatives of Z. latifolia are the American wild rices Z. aquatica L. and Z. palustris L., both annual species without rhizome.

More research is needed on the relationship between plant host and fungal strains. Processing techniques should be improved.

• Petelot, A., 1954. Les plantes médicinales du Cambodge, du Laos et du Vietnam [Medicinal plants of Cambodia, Laos and Vietnam]. Vol. 3. Archives des Recherches Agronomiques et Pastorales au Vietnam No 22. pp. 294-295.
• Pham Sy Lang & Dao Ngoc Dang, 1975. Cay cu nieng lam thuc an gia suc o vung dong chiem Binh Luc - Nam Ha [Zizania latifolia as a fodder crop at Nam Ha]. Khoa hoc va ky thuat nong nghiep [Science et Technologie Agricole] 5: 346-349.
• Terrell, E.E. & Batra, L.R., 1982. Zizania latifolia and Ustilago esculenta, a grass-fungus association. Economic Botany 36(3): 274-285.
• Thrower, L.B. & Yuk-Sim Chan, 1980. Gau sun: a cultivated host-parasite combination from China. Economic Botany 34(1): 20-26.

• Nguyen Tien Hiep