Dioscorea alata
Dioscorea alata
The Purple yam (Dioscorea alata L.) is a climbing shrub species belonging to the Dioscoreaceae family.
Systematics –
From a systematic point of view, it belongs to
Eukaryota Domain,
Kingdom Plantae,
Liliopsida class,
Order Liliales,
Dioscoreaceae family,
Genus Dioscorea,
Species D. alata.
The terms are synonymous:
– Dioscorea atropurpurea Roxb .;
– Dioscorea globosa Roxb .;
– Dioscorea javanica Queva .;
– Dioscorea purpurea Roxb .;
– Dioscorea sativa Del .;
– Dioscorea vulgaris Miq ..
Etymology –
The term Dioscorea of the genus was dedicated to Pedanio Dioscorides Anazarbeo (of Anazarbo Asia Minor), doctor of Greek culture, botanist and pharmacist, who lived in the first century AD.
The specific alata epithet means endowed with wings, from wing to wing: due to its “winged stem” (large ridges along the square stem).
Geographic Distribution and Habitat –
Dioscorea alata is a plant native to the tropical areas of East Asia and Malaysia and the surrounding areas (Taiwan, Ryukyu Islands of Japan, Assam, lowland areas of Nepal, New Guinea, Christmas Island), where it is cultivated since ancient times.
The plant is widely cultivated in tropical zones for its edible root which, in prehistoric times, was dispersed by man in the Pacific Ocean and the Indian Ocean, and is now widespread in many regions of the world.
Its habitat in the wild is not known because the plant’s center of origin is unknown; however, archaeological evidence suggests that it has been exploited in Southeast Asian islands and New Guinea prior to the Austronesian expansion.
Description –
Purple yam is a vigorous, perennial climbing plant, producing annual stems up to 15 meters long from a very large tuberous base. These stems climb to the ground or twist into the surrounding vegetation. The stem is quadrangular and winged.
The plants produce air tubers that are tightly attached to the stems, close to the attachment of the leaves. These airplanes are brown-grayish and somewhat irregular in shape with a rough surface.
The leaves are long petalized, opposite (often with a single persistent leaf); blades up to 20 cm or more in length, closely heart-shaped, with often angular basal lobes.
It is a dioecious species, with both male and female plants.
The flowers are small, occasional, male and female from the axils of the leaves on separate plants; the male flowers are grouped in panicles up to 30 cm long; female flowers are collected in smaller spikes.
The fruit is a capsule consisting of 3 parts.
The seeds are winged.
Cultivation –
The Dioscorea alata has a dormancy period of at least two months, which facilitates its transportation and probably explains its wide diffusion.
The plant grows best in the tropical lowland areas up to an altitude of 1,000 meters with a temperature around 26 – 34 ° C, a well-defined dry season of 4 – 5 months and a total rainfall of 1,000 – 1,500 mm evenly distributed during the rest of the year.
The plant does not tolerate frost although among the many cultivars of this species, there are forms that tolerate a wide range of environmental conditions.
To obtain good harvests this species requires a deep, well-drained sandy substratum, which is not subject to water shortages. It also grows well in medium-clay soils, and the plants respond well to the application of organic matter; they also prefer a pH between 5.5 and 6.5, tolerating 4.8 – 8.5.
As for light conditions, they prefer day lengths over 12 hours during the first growing season as this favors vegetative growth; day lengths of less than 12 hours towards the end of the growing season will encourage tuber formation and development.
Each plant produces an average of 3 roots that usually weigh between 5 and 10 kg, although exceptionally they can weigh up to 60 kg.
Plants take 7-10 months to ripen a crop with yields of 20-25 tons per hectare.
Propagation can take place both by seed, which are rarely produced in cultivation, or by cuttings of tubers. In this case, small tubers can be cut into 2 – 4 sections, the larger tubers into 6 – 8 sections. Each section should have 2-3 dormant buds. The cut tuber is often left in the sun for several hours to promote wound healing and reduce the risk of fungal infection.
Aerial tubers can also be used, usually producing vigorous plants.
Customs and Traditions –
Dioscorea alata, as mentioned, is a plant native to the tropical areas of Asia where it has been a staple food since ancient times.
According to ancient remains that have come down to us from the caves of the Niah National Park (Malaysia) prior to 40,000 BC. and from the Ille cave of the Dewil Valley (Philippines), dating back to around 11000 BC, humans consumed Dioscorea alata and Dioscorea hispida during the Late Pleistocene in Southeast Asia. Being a sterile polyploid, the Dioscorea alata cannot cross bodies of water. This shows that these plants were exported to the islands of the Pacific Ocean and New Zealand only during the Austronesian expansion, which occurred approximately between 5000 and 2500 BC.
It is one of various yam species that have been independently domesticated and grown in the Islands of Southeast Asia and New Guinea for their starchy tubers, including round yam (Dioscorea bulbifera), ubi gadong (Dioscorea hispida) , the lesser yam (Dioscorea esculenta), Pacific yam (Dioscorea nummularia), fiveleaf yam (Dioscorea pentaphylla) and pencil yam (Dioscorea transversa). Among these D. alata and D. esculenta were the only ones regularly grown and consumed, while the rest were usually considered famine food because of their higher levels of dioscorin toxin which requires them to be properly prepared before consumption.
In particular, D. alata is more cultivated than D. esculenta, largely because of its much larger tubers.
D. alata and D. esculenta were best suited for long transports on Austronesian ships and were transported through all or most of the Austronesian expansion zone. In particular, D. alata was introduced in the Pacific islands and in New Zealand. These two species were also transported by Austronesian travelers to Madagascar and the Comoros.
Dioscorea alata is a major crop in Southeast Asia today, particularly the Philippines, where the vividly purple variety is widely used in various traditional and modern desserts. It also remains important in Melanesia, where it is also grown for ceremonial purposes related to the size of the tubers at the time of harvest. Its importance in Eastern Polynesia and New Zealand, however, declined after the introduction of other crops, most notably the sweet potato.
The tubers are edible and have a slightly sweet, earthy and rich flavor reminiscent of sweet potatoes or taro. The violet cultivars, in particular, give the dishes a particularly vivid violet color due to the high amount of anthocyanins. They are also valued for the starch that can be made.
This plant is most commonly associated with traditional and modern Filipino cuisine (where it is known as ube or ubi). It is widely used for a variety of Filipino desserts, as well as an ingredient – flavor for ice cream, milk, sandwiches, donuts, pies, cookies, cakes, jams and other types of sweets.
Purple yam is commonly confused with purple varieties of sweet potatoes because of their similarities in color, taste, and culinary uses. However, like other yams, purple yams tend to have a wetter texture than sweet potatoes. Purple yams also have a higher anthocyanin content than sweet potatoes and can be used interchangeably in most recipes.
Dioscorea alata is also used as a medicinal plant.
The tuber is grated, mixed with strong brown vinegar, then spread out on paper and placed on a woman’s lower back to prevent a risk of miscarriage.
In folk medicine it has been used as a moderate laxative and vermifuge, and for fever, gonorrhea, leprosy, tumors and inflamed hemorrhoids. This plant has relatively high levels of oxalates (486–781 mg / 100 g of dry matter).
Among other possible uses it is recalled that the color of the purple varieties is due to various anthocyanin pigments that are soluble in water and have been proposed as possible food colors.
Moreover, Dioscorea alata is sometimes cultivated in gardens for its ornamental value.
This plant escaped its native growth area and entered the wild in many other places, naturalizing in parts of southern and central-eastern China, Africa and Madagascar, the western hemisphere, and various islands of the Indian and Pacific oceans. It persists in the wild in Haiti, as well as in the United States in particular in Louisiana, Georgia, Alabama, Puerto Rico, the US Virgin Islands and Florida where it is technically considered an invasive species.
The raw tuber of this plant is toxic and is said to produce narcosis, and the presence of saponins makes cooking necessary to make the tubers safe to eat.
Preparation Method –
Purple yam is a plant that is consumed by its cooked tubers. Usually boiled or baked and used as a vegetable; Proper cooking is recommended because, as said, it can be toxic if consumed raw.
The consumption of this prevalent plant is boiled, baked, or as a sweet sweet called ube halayá; the latter is a popular ingredient in the icy dessert called halo-halo. Purple Yam desserts have more recently entered the United States through Filipino cuisine, under the Filipino name “ube.” It is particularly appreciated for the striking purple color it gives to desserts.
In Maharashtra, “chips” made from these tubers, stir-fried are eaten during religious fasting. This plant is an essential ingredient in Undhiyu and is also a popular dessert in Jaffna, Sri Lanka.
This plant is also used in medicine. In particular, the tubers are grated, mixed with strong brown vinegar, then spread out on paper and placed on the lower back of women to prevent the risk of miscarriage.
Guido Bissanti
Sources
– Acta Plantarum – Flora of the Italian Regions.
– Wikipedia, the free encyclopedia.
– Useful Tropical Plants Database.
– Conti F., Abbate G., Alessandrini A., Blasi C. (ed.), 2005. An annotated checklist of the Italian vascular flora, Palombi Editore.
– Pignatti S., 1982. Flora d’Italia, Edagricole, Bologna.
– Treben M., 2000. La Salute from Pharmacy of the Lord, Advice and experiences with medicinal herbs, Ennsthaler Editore.
Caution: Pharmaceutical applications and alimurgical uses are indicated for informational purposes only, they do not represent in any way a medical prescription; therefore no responsibility is taken for their use for curative, aesthetic or food purposes.