6694

2: Edible fruits and nuts

Syzygium malaccense (L.) Merr. & Perry

Syzygium malaccense: J. Arnold Arbor. 19: 215 (1938).

MYRTACEAE

2n = 44 for Syzygium aqueum, 22 for Syzygium malaccense; varying figures (e.g. 33, 42, 44, 66, 88) are given for Syzygium samarangense.

— Syzygium malaccense: Eugenia malaccensis L. (1753), Jambosa malaccensis (L.) DC. (1828), Eugenia domestica Baillon (1876).

— Syzygium malaccense: Malay apple, pomerac (En). Pomme malac, poirier de Malaque (Fr). Indonesia: jambu bol. Malaysia: jambu merah, jambu bol. Philippines: yanbu, tersana, makopang-kalabaw (Tagalog). Burma: thabyo-thabyay. Thailand: chomphu-mamieo, chomphu-saraek (central), chomphu-daeng. Vietnam: cay dao, cay roi.

All 3 species presumably originated in South-East Asia, Syzygium aqueum occurring more widely and Syzygium malaccense being more restricted to Java, Sumatra and Peninsular Malaysia. Current distribution ranges from India through South-East Asia to the Pacific Islands (the Malay apple features in Fijian mythology). Syzygium samarangense is the more popular of the three in South-East Asia; Syzygium malaccense is also grown in appreciable numbers in Central and South America. The trees are cultivated in home gardens, often planted along driveways and paths.

The trees are grown for their fruit, which substitute for one another in the marketplace. Whereas Malay apple can easily be recognized, it is not easy to distinguish between the various water apple and wax jambu fruits. The ripe fruit is sweet — water apple remaining somewhat astringent — and is mainly eaten fresh. In Malaysia a water apple salad used to be served at the ceremony after childbirth. In Indonesia water apple and wax jambu are used in fruit salads ('rujak') and they are also preserved by pickling ('asinan'). Malay apples are often stewed with other fruit to tone down the sour taste of the latter. Indonesians use young water apple leaves to wrap snacks of fermented sticky rice.
Various parts of the tree are used in traditional medicine, and some have in fact been shown to possess antibiotic activity. In particular the bark, leaves and roots of Malay apple are used against different ailments in a number of countries, also outside Asia (e.g. Hawaii, Brazil). The wood is reddish and hard and, in wax jambu and Malay apple, grows to dimensions large enough for construction purposes.

Much of the home-grown fruit reaches the market and almost throughout the year one or another of the 3 fruits is available. Export is limited to some border trade, e.g. to Singapore.

Whereas the water apple is a watery, thirst-quenching fruit with a glistening, almost translucent skin, the wax jambu is glossy — indeed wax-like — and the flesh is rather dry. The flavour is aromatic and the quality of the best strains is not surpassed by the other species. The Malay apple is usually red with pink or white streaks; the flesh is thick, rather dry and scented, but often insipid.
Eighty per cent or more of the fruit is edible. The composition of all 3 species is similar per 100 g edible portion: water more than 90%, protein 0.3 g, fat none, carbohydrates 3.9 g, fibre 1 g, vitamin A 253 IU, vitamin B₁ and B₂ traces, vitamin C 0.1 mg, energy value 80 kJ/100 g (analysis for wax jambu in Thailand). In all 3 species some plant parts are astringent because of the presence of tannins.

— Syzygium malaccense. Tree, 5—20 m tall, with straight trunk, 20—45 cm diameter, often branched near the base and with broadly ovoid canopy. Leaves opposite, elliptic-oblong, 15—38 cm x 7—20 cm, thick-coriaceous, petiole 0.5—1.5 cm long, thick, red when young. Inflorescences exclusively on defoliate twig-parts, short and dense, 1—12-flowered; flowers 5—7 cm in diameter, red; calyx tube ventricose towards apex, 1.5—2 cm long, with broad lobes 4—8 mm long; petals 4, oblong-ovate or orbicular-ovate, up to 2 cm long, dark red; stamens numerous, up to 3.5 cm long, with red filaments; style 3—4.5 cm long, red. Fruit a berry, ellipsoid, 5—8 cm in diameter, crowned by the incurved non-fleshy calyx segments, dark red or purplish-yellow or yellow-white; flesh 0.5—2.5 cm thick, juicy, white, fragrant. Seed 1 per fruit, globose, 2.5—3.5 cm in diameter, brown.

Seeds lose their viability quickly and should be sown fresh from the fruit. Polyembryony occurs in the genus and has been observed in Malay apple seed. Shoot growth proceeds in flushes which are more or less synchronous, depending on the climate. The juvenile period lasts for 3—7 years, water apple usually being the first to come into bearing. Bearing of clonal trees starts after 3—5 years. There are definite flowering seasons, often two, sometimes three in a year, but the timing varies from year to year. Water apple and wax jambu commonly flower early or late in the dry season; the flowers appear to be self-compatible and the fruit ripens 30—40 days after anthesis. There seems to be no regular growth rhythm for Malay apple. Apparently the trees are triggered into bloom (by wet weather following a dry period) more readily than water apple and wax jambu trees; at any rate, Malay apple usually has the most crops per year. Malay apples ripen about 60 days after bloom.

All three species show much seedling variation and several forms are recognized by fruit colour (e.g. white, green or pink for wax jambu) and taste (e.g. sweet and sour forms of water apple). In Thailand wax jambu clones have cultivar status, e.g. the green-fruited 'Khiew Savoey'.

The trees are at home in fairly moist tropical lowlands up to 1200 m elevation. Malay apple is restricted to the wetter climates, whereas water apple and wax jambu do best in areas with a fairly long dry season. This does not mean that the latter are drought-resistant: all 3 species require a reliable water supply and are often planted along streams or ponds. The trees prefer heavy soils and easy access to water instead of having to search for water in light deep soils.

Propagation from seed is common. Seeds are sometimes abortive, and some wax jambus tend to be seedless. Clonal propagation through air layers, cuttings or budding is not difficult. Air layering is commonly employed in South-East Asia. The modified Forkert method is recommended for budding. Seedlings of the same or other Syzygium species are used as rootstocks. In Java 'jambu klampok' or 'kopo' (Syzygium pycnanthum Merr. & Perry, syn. Eugenia densiflora (Blume) Duthie) is recommended as rootstock because it is hardy and not attacked by termites.
Tree spacing ranges from 5—7 m for water apple and 6—8 m for Malay apple trees, to 8—10 m for wax jambu trees. The trees receive little attention after the first year or two when manuring, weeding, mulching and watering ensure rapid increase of tree volume. Trees which bear well benefit from compound fertilizers applied after harvest and supplemented with a top dressing as soon as the inflorescences are being formed. There appears to be no experience with pruning or fruit thinning. There are no specific recommendations for crop protection, but the incidence of pests and diseases certainly warrants a study of the causal organisms and their control.
Good crops can be produced. A five-year-old wax jambu may yield 700 fruit and for Malay apple yields of 20—85 kg/tree are reported. The fruits have a thin skin and are delicate; they need to be picked by hand twice a week and handled with care. The fruit should be consumed or preserved within a few days from harvest.

There is no information on germplasm collections; genetic erosion is considered serious in all 3 species. Breeding work may be premature but everyone agrees that there is much scope for selection of superior forms. The Institute of Plant Breeding in Los Baños has trees of several clones of wax jambu and Malay apple, but formal trials are needed to compare the more promising forms.

Fruit science has paid little attention to these crops, presumably because they are not planted in orchards, and because the short shelf life limits possibilities for commercialization. Nevertheless there is a ready market for the home-grown fruit, indicating that the fruit is quite popular. Growth and development of the trees need to be observed more closely to gain a better insight into the growth rhythm, including the timing and intensity of bloom, and quantitative aspects of yield. In so doing the basis is also laid for selection of superior types.

Koorders, S.H. & Valeton, Th., 1900. Bijdrage No. 6 tot de kennis der boomsoorten op Java [Contribution No 6 to the knowledge of tree species in Java]. Mededeelingen uit 's Lands Plantentuin No 40. pp. 80—82, 55—57, 63—66.
Morton, J., 1987. Fruits of warm climates. Creative Resource Systems, Winterville, N.C. pp. 378—383.
Molesworth Allen, B., 1967. Malayan fruits. Donald Moor Press Ltd., Singapore. pp. 115—125.
Okuda, T.T., Yoshida, Hatamo, T., Yazaki, K. & Ashida, M., 1982. Ellagitannins of the Casuarinaceae, Stachyuraceae and Myrtaceae. Phytochemistry 21(12): 2871—2874.

G. Panggabean

Panggabean, G., 1991. Syzygium malaccense (L.) Merr. & Perry. 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