Ipomoea batatas (L.) Lamk
Family
Convolvulaceae
Synonyms
Convolvulus batatas L., Convolvulus edulis Thunb., Batatas edulis (Thunb.) Choisy.
Vernacular Names
| Malaysia | Ubi keladi, ubi keladek. |
| English | Sweet potato. |
| Indonesia | Ubi jalar (General), ketela rambat (Javanese), huwi boled (Sundanese). |
| Papua New Guinea | Kaukau (Pidgin), kaema (Motu). |
| Philippines | Kamote, kamuti. |
| Burma (Myanmar) | Myonk-ni. |
| Cambodia | Dâmlô:ng chvië. |
| Laos | Man kè:w. |
| Thailand | Man-thet. |
| Vietnam | Khoai lang. |
| French | Patate douce. |
Geographical Distributions
It is generally accepted that Ipomoea batatas is originated from Central America or the northern part of South America. This acceptance is based on archaeological finds, the distribution patterns of wild species, and variation in cultivated clones. Three lines of dispersion from the centre of origin to other regions have been postulated based on linguistic evidences:
i) the ‘kumara’ line: prehistoric transfer from the northern part of South America to eastern Polynesia;
ii) the ‘batatas’ line: introduction to Africa and Asia through Europe from the first voyage of Columbus;
iii) the ‘kamote’ line: direct transfer from Mexico to the Philippines via Hawaii and Guam in the 16th Century.
Now, I. batatas is an established crop which is widely grown in the tropical, subtropical and warm temperate regions.
Description
I. batatas is a perennial herbaceous plant. The root system is with fibrous, adventitious roots and enlarged roots which is derived from secondary thickening of some adventitious roots, serving as a storage organ, variable in shape, size, number, skin colour (white, yellow, brown, red, purple) and flesh colour (white, yellow, orange, purple).
The stems are prostrate or ascending, or occasionally twining, measure 1-8 m long and much branched from several nodes.
The leaves are arranged spirally with a phyllotaxy of 2/5, simple and lacking stipules. The petiole is 5-30 cm long, with 2 small nectaries at the base and grooved above. The lamina is usually ovate, measuring 4-15 cm x 4-12 cm, entire and with angular or palmately lobed.
The flowers are an axillary, solitary or in cymes. The pedicel is 3-18 cm long. The sepal is with 5-lobed. The petal is funnel-shaped, white or lavender and with a purple throat. There are 5 stamens that unequal length and attached near the base of the petal. The ovary is surrounded by a lobed orange nectary, with a 2-lobed stigma and it is white or pale purple.
The fruit is a 5-8 mm long capsule with 1-4 seeds. The seed measures about 3 mm long, black and usually with a very hard testa.
Ecology / Cultivation
I. batatas is grown between latitudes 48°N and 40°S. At the equator, it is grown at altitudes ranging from sea level to 3000 m altitude. Its growth is maximum at temperatures above 25°C and when temperatures fall below 12°C or exceed 35°C, the growth is retarded. Dry matter production increases with increasing soil temperatures from 20-30°C, but declines above 30°C. It is a quantitative short-day plant in terms of flowering response.
I. batatas is a sun-loving crop; however, it can tolerate a 30-50% reduction of full solar radiation. Light saturation of single leaf photosynthesis occurs at around 800 µE/m2 per second and light intensity is required for saturation in the canopy increases with increasing a leaf area index. The optimum leaf area index in the field is 3-4 at solar radiation of 380 gcal/cm2 per day. The photosynthetic rate of the canopy in the field is highest between 10 a.m. and 2 p.m.
I. batatas grows best with a well-distributed annual rainfall of 600-1600 mm during the growing season. Dry weather favours the formation and development of storage roots. Soil moisture at 60-70% of field capacity is favourable for the initial phase, 70-80% for the intermediate phase, and 60% for the final phase. I. batatas is relatively drought tolerant, mainly because of its capacity for regeneration and root penetration. However, it cannot withstand long periods of drought; the yield is considerably reduced if drought occurs about the time of storage root initiation.
The crop can be grown on a wide range of soil types, but a well-drained and sandy loam with clayey subsoil are considered ideal. It cannot stand waterlogging and usually grown on mounds or ridges. Poor aeration or oxygen concentration less than 10% in the soil in the initial phase increases the degree of lignification of stele cells and suppresses the primary cambium activity, resulting in young roots developing into fibrous roots. At the final phase, it restrains the secondary cambium activity, favouring vine development at the expense of the storage roots. Flooding shortly before harvesting may result in storage roots rotting in the soil or during subsequent storage. The best bulk density of the soil is 1.3-1.5 g/ml. Higher bulk densities tend to reduce storage root formation, resulting in reduced yields or poorly shaped storage roots. The optimum soil pH for I. batatas is 5.6-6.6, but it grows well even in soils with a relatively low pH, e.g. 4.2. It is sensitive to alkaline or saline soils; the maximum soil salinity without yield loss (threshold) is about 1.5 dS/m.
Line Drawing / Photograph
References
- Plant Resources of South-East Asia No. 9: Plants yielding non-seed carbohydrates.
