Pachyrhizus erosus (L.) Urban
Family
Leguminosae
Synonyms
Dolichos erosus L., Pachyrhizus angulatus Rich. ex DC., Pachyrhizus bulbosus (L.) Kurz. Sometimes erroneously spelled ‘Pachyrrhizus‘.
Vernacular Names
| Malaysia | Sengkuwang, bengkuwang, mengkuwang. |
| English | Yam bean. |
| American | Chop suey bean, jicama. |
| Indonesia | Bengkuang (General), besusu (Javanese), bangkowang (Sundanese). |
| Cambodia | Pe’ kuëk. |
| Laos | Man ph’au. |
| Thailand | Man-kaeo (General), huapaekua (Peninsular), man-lao (Northern). |
| Vietnam | C[ur] d[aaj]u (Northern), s[aws]n (Southern). |
| Philippines | Sinkamas (Tagalog), kamias (Ilokano). |
| French | Dolique bulbeux, pois batate. |
Geographical Distributions
Pachyrhizus erosus originated in Mexico and Central America as far south as Costa Rica. The crop has been known in cultivation in this region from approximately 1000 BC. It was originally introduced to the Far East by the Spanish via the Acapulco-Manila route, reaching Amboina prior to the end of the 17th Century. P. erosus is presently found in cultivation (or escaped and naturalised) pantropically.
Description
P. erosus is a perennial, herbaceous, strigose to hirsute, climbing or trailing vine that can reach up to 2-6 m long. The roots are tuberous where in cultivation is one turnip-shaped tuber per plant while in the wild types are numerous elongated tubers per plant. The tubers of cultivars measuring up to 30 cm x 25 cm, skin cream or light to dark brown and flesh white to whitish-yellow.
The leaves are trifoliolate, hairy and with dentate, palmatilobed or entire leaflets. The lateral leaflets are obliquely rhomboidal to ovate, measuring 2.5-10.5 cm x 2.5-18 cm and with 3-veined from the deltoid base. The terminal leaflet is ovate to kidney-shaped, measuring 3.5-17.5 cm x 4-21 cm and 3-5-veined from the wedge-shaped base.
The inflorescence is a many-flowered pseudoraceme and measures up to 55 cm long. The pedicel is hirsute and measures up to 1(-2) cm long with caducous and sericeous prophylls. The flowers are 1-2.5 cm long. The sepal is brown, hirsute both internally and externally and measures about 1 cm long. The upper lobe is formed by 2 adaxial sepals fused that almost to the tip. It is 2.5-7.5 mm long and with a 2.5-6.5 mm long tube. The 3 lobes are acute and shorter than the tube. The petal is violet-blue or white, standard, with eared wings and hairless keel. The stamens are about 1-2 cm long while the anthers are elliptical and dorsifixed. The ovary is subsessile, multi-ovulate, with a crenulate disk round its base, recurved style and ventrally ciliated. The stigma is nearly spherical vertical surface.
The fruit is a legume, linear-oblong, measuring 6-13 cm x 8-17 cm and with a septate between seeds internally. It is slightly too deeply contracted between seeds externally, strigose to hirsute when young and often smooth at maturity.
The seed is flat, square to rounded, measuring 3-9 mm x 4-9 mm and olive green to brown or dark reddish brown. The seedling is with hypogeal germination where the first pair of leaves is simple and usually entire.
Ecology / Cultivation
P. erosus is quite tolerant of differences in climatic and edaphic conditions, but it is generally associated with regions having moderate precipitation (often seasonal) or high precipitation with well-drained soils. In Mexico, it grows up to 1400 m altitude. The optimum daytime temperature level is (21-)24(-28)°C with day length approaching 12 hours. However, field trials indicate that the nocturnal temperature may be as important in obtaining optimal yields. Both tuber growth and flowering are initiated by decreasing day length (and night temperature). A well-drained soil, alluvial or volcanic, is preferable, as the crop does not tolerate waterlogging. In areas with high precipitation, cultivation on ridges is recommended.
Line Drawing / Photograph
References
- Plant Resources of South-East Asia No. 9: Plants yielding non-seed carbohydrates.
