Citrus aurantifolia (PROSEA)
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Introduction |
Citrus aurantifolia (Christm. & Panzer) Swingle
- Protologue: J. Wash. Acad. Sci. 3: 465 (1913).
- Family: Rutaceae
- Chromosome number: 2n= 18
Synonyms
- Limonia aurantifolia Christm. & Panzer (1777),
- Citrus javanica Blume (1825),
- Citrus notissima Blanco (1837).
Vernacular names
- Lime, sour lime, common lime (En)
- Lime acide, limettier (Fr)
- Indonesia: jeruk nipis, jeruk pecel
- Malaysia: limau asam, limau nipis
- Papua New Guinea: muli (Pidgin)
- Philippines: dayap
- Cambodia: krôôch chhmaa muul
- Laos: naaw
- Thailand: somma nao, manao
- Vietnam: chanh, chanh ta.
Origin and geographic distribution
Lime is believed to have originated in northern India and adjoining parts of Burma, or in northern Malesia. Amazingly there are no records of wild lime in Thailand. The lime is now cultivated throughout the tropics and in warm subtropical areas.
Uses
The fruit is used in nearly every home in South-East Asia, mainly to flavour food, but also to prepare drinks and for a variety of medicinal applications. The rich flavour and acid taste make lime a favourite for hot and spicy dishes, either fresh or in the form of pickles and sauces. The refreshing qualities come to the fore in lime juice, lime tea and the use on other fruit, e.g. papaya. In Malaysia the fruit is preserved in brine and vinegar; it is enjoyed as an appetizer when fried in oil with sugar added.
The leaves and fruits have many medicinal uses, some of which are linked with the belief that limes drive evil spirits away.
Production and international trade
According to FAO statistics the world produced 6 million t of limes and lemons ( Citrus limon (L.) Burm.f.) in 1988, the figures showing a rising trend. The lime crop is by far the smaller of the two, but since lemons are hardly grown in South-East Asia, the following FAO figures must refer to limes: Cambodia 1000 t, Laos 8000 t, Malaysia 3000 t, Thailand 1000 t. Statistical data from Thailand give a more realistic production estimate of 53 600 t from a total area of 29 100 ha in 1987/1988. Trade statistics show that exports from Indonesia, the Philippines and Thailand are insignificant in relation to domestic consumption. Large-scale production for the international trade in juice and oil is mainly found in Central America (hence the names Mexican lime or West Indian lime), Dominica and Ghana.
Properties
The mature yellow fruit usually has a thin rind and a very acid juice: 7-8% citric acid by weight. The juice extract is about 41% of the fruit weight. Analyses in Thailand give the following composition per 100 g edible portion: water 91 g, protein 0.5 g, fat 2.4 g, carbohydrates 5.9 g, fibre 0.3 g, vitamin A 17 IU, vitamin C 46 mg; energy value is about 150 kJ per 100 g.
Description
- Small, densely and irregularly branched, evergreen tree, about 5 m tall; twigs armed with short stiff sharp spines.
- Leaves alternate, elliptic to oblong-ovate, 4-8 cm × 2-5 cm, margin crenulate; petioles narrowly winged.
- Inflorescences short axillary racemes, 1-7(-10)-flowered; flowers small, white in bud; calyx cup-shaped, 4-6-lobed; petals 4-6, 8-12 mm long; stamens 20-25(-34), ovary 9-12(-15)-celled, style abruptly distinct.
- Fruit a globose to ovoid berry, 3-6 cm in diameter, sometimes with apical papillae, greenish-yellow; peel very thin, very densely glandular; segments with yellow-green pulp-vesicles, very acid, juicy and fragrant.
- Seeds small, plump, ovoid, pale, smooth with white embryos (polyembryonic).
Growth and development
Seedlings are largely true to type because of polyembryony. The juvenile phase lasts about 5 years. Root suckers and suckers on older branches, characterized by stout sharp spines, are common. Lime is an everbearing tree. Flowers are either perfect or male and borne in inflorescences of up to 10 flowers in the leaf axils of mature shoots, but are often single in the axils of a shoot which has just flushed. The stigma is receptive as the flower opens and remains so for a few days. Pollen is not released until the flower has opened. Copious secretion of nectar by a floral disk attracts insects, especially honey bees, which pollinate the flowers. Self-pollination occurs, but self-incompatibility limits fruit set.
Fruit requires 5.5-6 months from flowering to harvest. In Thailand there is little fruit in March-April. This may be due to early ripening (colouring) of the fruit during the cool dry period of December-February. Alternatively, the gap in supplies may be caused by poor flowering or fruit set during September-October (the second half of the rainy season).
Other botanical information
Limes hybridize freely with other Citrus species, and many hybrids are known, e.g. Lemonimes ( lime × lemon), Limequats (lime × kumquat).
Limes are divided horticulturally into acid and sweet limes. In addition to the common (Mexican, West Indian or Key) lime described, there is the Tahiti or Persian lime (2 n = 3x = 27), presumably a hybrid of lime and citron ( Citrus medica L.). It has a longer, globose fruit, acid but less richly flavoured than the common lime; the fruit is seedless or nearly so. The Tahiti lime is more hardy and successful in the subtropics; in South-East Asia it plays a very minor role. The sweet lime is thought to be a hybrid of the lime and a sweet lemon or sweet citron, probably from India, where it is of some importance. It has been used as a rootstock.
Lime cultivars are not very distinct; in Thailand "Kai" and "Paan" can only be identified by fruit shape (ovoid and flattened/globose respectively).
Ecology
The lime is at home in the lowland tropics, although it grows up to 1000 m altitude or more. The tree is sensitive to cold but is quite drought-resistant. High incidence of bacterial canker is a limiting factor in the wet tropics; under dry conditions irrigation is necessary to obtain good quality fruits. Limes can grow on poor soils and tolerate heavier soils than oranges, provided that good drainage prevents waterlogging.
Propagation and planting
Unlike other citrus species, limes are rarely propagated by budding. In South-East Asia air layering is the normal method, elsewhere the trees are raised from seed. Sturdy twigs, preferably suckers, are selected for layering and the dust of coconut husk after fibre extraction is the medium used in Thailand. The layers are potted and nursed for 2-4 weeks before planting.
Husbandry
Unpruned trees have a dense twiggy canopy and crowded branches may die back due to competition. Hence, trees are pruned to thin the branches and to remove suckers and limbs infected by canker. To influence the harvest time, irrigation is withheld for 3 weeks in the dry season; resumption of irrigation triggers a flush which brings on flowering.
Diseases and pests
Limes are susceptible to tristeza virus, but the more serious threat is bacterial canker ( Xanthomonas campestris p.v. citri ), which shortens the life of trees by girdling the trunk. The bacteria can infect any part of the tree through wounds; even the stings of sucking insects afford entry. The bacteria are distributed by rain. Strict orchard hygiene, i.e. removal of infested branches, spraying with copper early in the rainy season, and spraying with streptomycin are recommended.
The obnoxious citrus leaf miner ( Phyllocnistis citrella ) causes leaf malformation and early leaf fall. The pest affects almost every tree and to the extent that flowering is diminished. Control by insecticides is difficult because the caterpillars are relatively safe in their tunnels in the underside of the leaves, and life cycles are short and overlap. Increased use of insecticides seems to have aggravated the pest, perhaps because predators are more vulnerable.
Harvesting
The fruit is harvested by hand when it is mature green or yellow. Immature fruit, although less juicy, may be included during the season of poor supplies.
Yield
Layered trees can produce fruit in the second year after planting, but growers aim at maximum growth to get a more substantial crop in the third year. The average yield of lime in Thailand during the 1988/1989 season was 2400 kg/ha. In India trees are expected to bear 600-1500 fruits per year.
Handling after harvest
Fruit is graded and sorted by hand. During post-harvest handling the appearance of the fruit quickly deteriorates as the rind dries out and turns dark. Trials to extend the storage life, including storage in moist sand, cool storage in combination with the use of polythene bags or waxing, gibberellin treatment and use of fungistats, have yielded no satisfactory results.
Prospects
Limes are an everyday ingredient of the food in South-East Asia. A single tree in the home garden can meet a family's requirements. Urban people depend on fruit produced in orchards. The main challenges for fruit growers are to raise the yield level and to manipulate the trees in order to produce fruit during the off-season when prices are high. A third challenge is to extend the storage life of the fruit. Indications are that there is much latent demand waiting for increased supplies.
Literature
- Kosiyachinda, S., Amatirattana, D. & Kosittrakul, M., 1985. Quality and composition of limes (Citrus aurantifolia; C. latifolia and C. mitis). ASST Newsletter 18(6): 403-413 (in Thai).
- Laohasiri, S., 1980. Studies on floral biology and fruit set of lime (Citrus aurantifolia Swing.). Undergraduate Special Problem, Department of Horticulture, Kasetsart University, Bangkok. 9 pp. (in Thai with English Abstract).
- Moncur, M.W., 1988. Floral development of tropical and subtropical fruit and nut species. CSIRO, Melbourne. pp. 154-157.
- Sethpakdee, R., 1989. Flower and fruit thinning in lime with NAA. The Second National Plant Growth Regulators Symposium, National Research Council of Thailand, Bangkok. pp. 153-156 (in Thai).
- Swingle, W.T. & Reece, P.C., 1967. The botany of Citrus and its wild relatives. In: Reuther, W., Webber, H.J. & Batchelor, L.D. (Editors): The citrus industry. Revised edition. Vol. 1. University of California, USA. pp. 374, 573-580.
Authors
Ravie Sethpakdee
