1511

2: Edible fruits and nuts

Gnetum gnemon L.

Mant. 1: 125 (1767).

GNETACEAE

2n = 24

Gnetum acutatum Miq. (1860), Gnetum vinosum Elmer (1915).

— Gnetum gnemon L. var. gnetum: melinjo, Spanish joint fir (En). Indonesia: melinjo, belinjo, bagoe. Malaysia: meninjau, belinjau. Philippines: bago, banago. Cambodia: voë khlaèt. Thailand: peesae. Vietnam: gâm cây, bét.
— Gnetum gnemon L. var. tenerum Markgraf: Thailand: phak miang, phak kariang, liang.

Melinjo is found throughout South-East Asia (although it is not native to Java and Sumatra) and reaches north to Assam and east to Fiji. Cultivation is limited to South-East Asia.

The young leaves, inflorescences, and the young and ripe fruits are cooked in vegetable dishes. The seed is the most important part; the fruit is nothing more than a seed covered by a tough husk (the seed coat) and a thin, edible rind. It can be eaten raw but is usually cooked or preserved as flat cakes from which crisps are made. This is an important home industry in Java. After removal of the rind, the seed is heated carefully, the husk is broken and the hot kernel is pounded into a flat cake. The cakes are sun-dried, graded and packed for sale. A crisp snack ('emping') is prepared by puffing up the cakes in boiling oil.
A high quality fibre is extracted from the inner bark; it is used for the famous Sumba bow string, and for fishing lines and nets because the fibre is durable in sea water. The wood is of no particular value, partly because additional cambia lead to an anomalous stem structure.
Gnetum gnemon var. tenerum is an important leafy vegetable in southern Thailand.

The kernels are nutritious; 100 g (70—80 kernels) contains approximately: water 30 g, protein 11 g, fat 1.7 g, carbohydrates 50 g, ash 1.7 g; the energy value amounts to 1060 kJ/100 g. The leaves are rich in protein, minerals and vitamins A and C.
The young leaves of Gnetum gnemon var. tenerum are very nutritious. Per 100 g they contain: water 75.1 g, protein 6.6 g, fat 1.2 g, carbohydrates 9.1 g, fibre 6.8 g, ash 1.3 g, phosphorus 224 mg, calcium 151 mg, iron 2.5 mg and vitamin A 10 889 IU. The energy value is 310 kJ/100 g.

A slender dioecious evergreen tree with a straight domineering trunk, 5—10 m tall, grey, marked with conspicuous raised rings; trunk clad with numerous whorls of branches down to the base. Branches thickened at base. Leaves opposite, elliptical, 7.5—20 cm x 2.5—10 cm; secondary nerves bent, joining. Inflorescences solitary and axillary, also on older wood, 3—6 cm long with flowers in whorls at the nodes. Female flowers 5—8 at each inflorescence node, globose and tipped. Fruit nutlike, ellipsoid, 1—3.5 cm long, shortly apiculate, almost velvety, yellow turning red to purple when ripe. Seed 1 per fruit, large and horny.
Embryogeny may not be completed by the time the seed is shed; further development occurs on the ground. Seeds take several months to 1 year to germinate. The juvenile phase lasts 5—8 years. Twigs flush and flower throughout the year, but the climate in the major centres imposes a degree of synchrony, often leading to two distinct harvest periods per year.
Six botanical varieties are distinguished. Cultivated trees belong to Gnetum gnemon var. gnemon, characterized by its tree habit and large fruit size. It is native to the Philippines, Sulawesi and Sumba and eastwards to New Guinea and Fiji, but often naturalized in secondary forests elsewhere in South-East Asia. The other varieties are shrubs with much smaller fruit. Gnetum gnemon var. tenerum is a 3 m tall shrub with oblong, beaked flowers and fruits with an acute apex (var. gnemon: flowers globose, fruit apex obtuse).

The tree occurs wild in rain forests at elevations up to 1200 m; it is common on river banks in New Guinea. Areas with a distinct dry season seem to be preferred for cultivation, probably because of the concentrated harvest in such environments. There appear to be no specific requirements with respect to soil quality and depth, but adequate moisture retention, seepage water or irrigation is necessary to bridge the dry season. The tree has been recommended for environmental protection (regreening) programmes.

The tree is propagated from seed and by air layering; propagation by cuttings or grafting is also possible. For a small number of trees, seedlings growing spontaneously under bearing trees can be collected and raised in a nursery until they are large enough to be planted. To obtain larger numbers of trees, large mature fruits which have dropped from the tree are collected. The rind is removed and the seed is dried in the shade and stored until a sufficient quantity has been gathered. The seed is pre-germinated in a box filled with alternating layers of seed and sand. After three months of watering daily, germination may be sufficiently advanced to transfer the seedlings to the nursery where they are raised — initially under shade — for six months or more, to be transplanted early in the rainy season.
Using air layers has the advantage that the best mother trees can be selected, that the young plant comes into bearing within 2—3 years after planting, and that only female (seed-producing) trees are obtained. The success of air layers depends on the place of cincturing: the top of the ring of bark to be removed should be at the edge of a swollen node. Rooting takes two months or more. The layers have to be nursed for some time after separation before field planting: they are pruned to balance top and roots, and raised in pots in the shade.
Melinjo is grown as a home garden tree or on field borders, but also in mixed orchards (e.g. near Jakarta) and even as a pure crop (e.g. near Batang, central Java). Trees are planted about 5 m apart and once established crop care is limited to occasional weeding.
The tree recovers readily from pruning which may be employed to limit tree height, to induce a flush of shoots for use as a vegetable, or to improve tree shape after repeated harvesting of shoots. It is not clear to what extent the harvesting of shoots interferes with fruiting. The inflorescences are borne on young shoots as well as on older branches. There is no information on pollination and fruit set. The trees are climbed to harvest the fruit; since the branches break easily, this is not without risk.
No pests or diseases have been reported, apart from borers and an unidentified sucking insect in Batang district that sometimes ruins the harvest. The trees may have to be guarded against rats and squirrels. There are only incidental records on yield and harvest period(s). In West Sumatra there is no clear season and large trees are reported to yield 20 000—25 000 fruits per year. In the Philippines the fruits mature early in the rainy season (June—July).
Gnetum gnemon var. tenerum plants are raised from seed, air layers or root suckers and planted 2 m apart, usually as intercrop between durian, rambutan, Parkia sp., etc. to benefit from the shade of the trees. Regular harvesting of the shoots controls the size and shape of the bushes.

A better insight into potential and actual yield levels is needed to assess the prospects of the crop. The technology of the preparation of emping could be improved and markets could be developed, even overseas. However, such developments depend on sizeable and reliable supplies: that is, on yield levels which make growing melinjo attractive in comparison with alternative crops.

Coronel, R.E., 1983. Bago (Gnetum gnemon Linn., Gnetaceae). California Rare Fruit Growers' Newsletter 15(3): 26.
Clifford, E.M. & Foster, A.S., 1988. Morphology and evolution of vascular plants. W.H. Freeman & Co. New York, USA. pp. 455—483.
International Board for Plant Genetic Resources, 1981. Vegetables. IBPGR Secretariat, Rome. pp. 42—43.
Kham-udom, K., 1986. Liang [Gnetum gnemon var. tenerum]. Thankasettakam 4(44): 61—64.
Rahardja, P.C., 1982. Bertanam melinjo. [Growing melinjo] P.T. Penebar Swadaya, Jakarta. 42 pp.
Rao, A.N. & Keng, H., 1975. Anomalous secondary growth in Gnetum gnemon. Annals of Botany 39: 973—974.

E.W.M. Verheij & Sukendar

Verheij, E.W.M. & Sukendar, 1991. Gnetum gnemon L.. In: Verheij, E.W.M. and Coronel, R.E. (Editors): Plant Resources of South-East Asia No 2: Edible fruits and nuts. PROSEA Foundation, Bogor, Indonesia. Database record: prota4u.org/prosea