Winged bean, multi-purpose tropical legume

The multi-purpose tropical bean yields tasty pods, which are rich in protein and vitamin A.

Among the tropical beans, known for their protein-rich pods and seeds, winged bean (Psophocarpus tetragonolobus) is considered quite unique because of its multiple uses. A native of South Pacific Islands, Papua New Guinea, it was introduced in India during 1799, and is grown in Assam, Tripura, Meghalaya, West Bengal, Orissa, and other southern States, according to Dr. G. S. Sahu, Assistant Professor, Department of Agriculture at the College of Horticulture, Orissa University of Agriculture and Technology (OUAT), Bhubaneswar, Orissa.

Also known as Goa bean, four-angled bean or asparagus pea, winged bean yields protein-rich pods, and its succulent leaves, tender shoots resembling lacy asparagus, seeds, flowers and tuberous roots are also edible. This robust, climbing herbaceous perennial, which reaches up to 5 metres in height, is also grown in different parts of the Philippines, Indonesia, and Malaysia. The tender pods, which are the most widely eaten part of the plant, can be harvested in two to three months of planting.

The long pods, which can reach up to 50 cm in length, are rich sources of proteins, carbohydrates and vitamin A (300 to 900 International Units). The pods may be eaten raw or used in salads, soups, stews and curries. The immature pods can also be used as peas. The seeds contain 29.8 to 39 per cent protein, 15 to 18 per cent fat and 23.9 to 42 per cent carbohydrate, according to him. The tender top three sets of leaflets can be eaten raw like spinach or cooked as greens. They are rich in vitamin A (20,000 IU), and 5 to 7.6 protein and 3 to 8.5 percent carbohydrates.

The vines produce starchy underground tubers. These tubers are eaten like potatoes, and are harvested 120 to 240 days after planting. The tuber formation is quite common in Papua New Guinea. In the Philippines, however, the tubers are relatively smaller and they are not eaten. The tubers are 2 to 4 cm in diameter and 8 to 12 cm in length. They contain 12.2 to 15 per cent protein (2 to 4 times higher than that of potato and 8 times more than that of cassava), 0.5 to 1.1 per cent fat and 27.2 to 30.5 per cent carbohydrate. This legume does well in humid tropics with high rainfall. It comes up well in loamy soils endowed with adequate drainage.

The plant responds well to organic nutrition and the application of biofertilizers, especially Rhizobium. Being a short-day length-loving plant, it flowers when the day length hovers just above 12 hours. Though, the plant is endowed with an extensive root system, it cannot stand drought conditions.

Courtesy- The Hindu, 26th September '02