Water-bamboo smut

Overview

Water-bamboo smut is the gall that the smut fungus Ustilago esculenta forms on the aquatic grass Zizania latifolia. The fungus swells the top three or four internodes of the young stem into a cone or spindle. The swollen tissue is mostly plant tissue, and it is eaten as a vegetable. The PROSEA account describes it as the only known vegetable that is the product of a plant host and a fungal parasite.

Host and gall

The host is Zizania latifolia, a perennial aquatic grass. Infected plants do not flower. The gall is about 5 to 10 cm long and 2 to 4 cm wide. Its firm green outer layer is removed, and the white inside is eaten. The catalogue classes it as a fungus-associated food rather than an ordinary mushroom fruit body.

Per 100 g of edible portion, the gall contains about 78.5 g water, 1.7 g protein, 4.7 g carbohydrate and 109 kJ, according to the PROSEA account.

Preparation

The white inner part is parboiled and then cooked. It is fried with meat and vegetables, or canned in brine. The gall is eaten as a vegetable, and the grains of the plant are used as food, sometimes ground into flour.

Cultivation

Plants are propagated vegetatively, from rhizome pieces or cuttings of immature culms that usually carry the smut. Fields are flooded to 10 to 20 cm and prepared much as rice paddies are, with organic fertiliser. Planting density is 10,000 to 30,000 plants per hectare. Galls appear four to five months after planting and are harvested one to two weeks later, with repeat harvests every one to two weeks. The PROSEA account states that no germplasm collections or breeding programmes exist.

The fungus is reported to raise the host's production of auxins and cytokinins, the plant growth hormones that drive the swelling. The fungus persists in the rhizome and culm.

Names and regions

Local names in the PROSEA account include gau sun in Cantonese, nomai-nam and kapek in Thailand, several Vietnamese names, and Manchurian wild rice and Manchurian water rice in English. The name jiaobai appears in the catalogue record and not in the PROSEA text.

The host is native to northeastern India, Burma, China, Japan, eastern Siberia and the Russian Far East. The gall is cultivated in China, Korea, Japan, Taiwan, Indo-China, Thailand, Burma and Malaysia, and locally by Chinese communities in Indonesia. It has been introduced to Europe, New Zealand and North America.

Other uses

The PROSEA account lists medicinal uses of the culms, rhizomes and grains against fevers. In Japan, smut spores mixed with oil were used on eyebrows and hair. In Europe the plant has been used for forage and paper.