Dioscorea esculenta (Lour.) Burkill
Family
Dioscoreaceae
Synonyms
Dioscorea aculeata L., Oncus esculentus Lour., Dioscorea tiliifolia Kunth.
Vernacular Names
| Malaysia | Ubi torak, kembili, kemarung. |
| English | Lesser yam, Chinese yam, Asiatic yam. |
| Indonesia | Ubi aung (West Java), ubi gembili (East Java), kombili (Ambon). |
| Papua New Guinea | Mami (Pidgin), taitu (Motu), kalak (Yatmei), diba (Hanuabada). |
| Philippines | Tongo (Tagalog), aneg (Ibanag), baribaran (Bikol). |
| Cambodia | Dâmlô:ng sya. |
| Laos | Hwà katha:d, man ‘o:nz. |
| Thailand | Man-musua (Central), man-chuak (Northern). |
| Vietnam | C[ur] t[uwf], khoai t[uwf], t[uwf] gai. |
| French | Igname des blancs, igname de Chine. |
Geographical Distributions
Dioscorea esculenta is native to Thailand and Indo-China, and may have originated there. It also grows wild in northern India, Burma (Myanmar) and New Guinea, but it is not known whether these are escape from ancient cultivation or real relicts of its natural distribution area. Within Southeast Asia, the main direction of pre-historic spread has been out of the continent of Asia through the Philippines, then south and south-east and ultimately towards the south-west. After 1500, it spread throughout the tropics. At present, its cultivation is the most important in Southeast Asia (especially in New Guinea), Oceania, the Caribbean and China.
Description
D. esculenta is an herbaceous, pubescent, often prickly and climbing annual. The roots are thorny in wild plants, often thornless in cultivated plants, fibrous and mostly confined to the top 1 m of the soil.
The tubers are 4-20 per plant and thrust downwards from a corm where on the stolons measure 5-50 cm long. The mature tubers are shortly cylindrical, sometimes lobed and measuring 8-20 cm x 2-5 cm. The skin is brown or grey-brown, thin and often rough with indurated bases of rootlets. The flesh is white.
The stem is cylindrical, twining to the left, prickly at the base and less to upwards. The bulbils are absent.
The leaves are arranged alternately, simple, cordate, measuring 10-15 cm x 10-17 cm, acuminate and with 9-13-nerved while the secondary veins are regular but not conspicuously ladder-like. The petiole is 1-1.5 times as long as the blade and often with 2 prominent spines at the base.
The inflorescence is unisexual. The male inflorescence is solitary in distal leaf axils, usually carrying one flower at a time along the axis but up to 70 or more in total while the female inflorescence is on down curved spike-like racemes, solitary from the upper leaf axils and measures up to 40 cm long.
The fruit is a reflexed capsule (very rare) and measuring 27 mm x 12 mm. The seed is winged all round.
Ecology / Cultivation
The natural habitat for D. esculenta is humid and sub-humid tropics. The plant grows best in a well-distributed rainfall of 875-1750 mm/year. Those parts of Southeast Asia without a dry monsoon are rather too humid for it. The average minimum temperature for a good growth is 22.7°C. Temperatures of 35°C and above can reduce sprouting of the planted set. The plant is essentially a lowland crop, but grows successfully at altitude of 900 m in the Himalayas. The maximum elevation for D. esculenta cultivation in Papua New Guinea is 900 m altitude. Tuber formation is promoted by short-day conditions. The light and well-drained soils of pH 5.5-6.5 are the best.
Line Drawing / Photograph
References
- Plant Resources of South-East Asia No. 9: Plants yielding non-seed carbohydrates.
