Coffea liberica (PROSEA)
Coffea liberica Bull ex Hiern
- Protologue: Trans. Linn. Soc. London, Bot. 1: 171, t. 24 (1876).
- Family: Rubiaceae
- Chromosome number: 2n= 22
Coffea dewevrei De Wild. & T. Durand (1899), C. arnoldiana De Wild. (1900), C. klainii Pierre ex De Wild. (1900), C. dybowskii De Wild. (1901), C. excelsa A. Chev. (1903), C. abeokutae P.J.S. Cramer (1913).
- Liberica coffee, Liberian coffee, excelsa coffee (En). Caféier liberica (Fr)
- Indonesia: kopi nangka
- Philippines: kapeng barako (liberica cultivars)
- Thailand: kafae-baiyai (central)
- Vietnam: cà phê dâu da, cà phê mít.
Origin and geographic distribution
Liberica coffee is native to tropical West and Central Africa. Nowadays, it is fairly widely cultivated especially in Guyana, Surinam, Bioko (Fernando Po), Sao Tomé, Liberia, Malaysia and the Philippines, and to a lesser extent also in Sierra Leone, Ivory Coast, Nigeria, Congo (Brazzaville), Mauritius, Sri Lanka, India, Thailand, Vietnam, Taiwan and on Timor. The first plantation of liberica coffee was established in Liberia in 1864, but reports of its cultivation go back to 1792. Its supposed resistance to coffee leaf rust disease resulted in a rapid introduction all over the world during the late 19th Century; it reached India in 1872 and Indonesia in 1875. In Indonesia it was cultivated quite extensively, but when it, too, proved to be susceptible to coffee leaf rust it was replaced by robusta coffee. In Peninsular Malaysia commercial cultivation started in 1880-1890.
Coffee, the hot watery extract from roast and ground seeds ("beans"), from C. liberica has a more bitter taste than that of the well-known arabica or robusta coffees. Although this is appreciated by certain groups in southern Peninsular Malaysia and Sabah, and in Africa, liberica coffee is generally drunk with lots of sugar and milk to mask the taste. It is also blended with other coffees, or used in mixtures with other liquids. The taste of excelsa coffee, which originates from a botanical variety of C. liberica , is less bitter than that of true liberica coffee.
Production and international trade
Although liberica coffee contributes only about 1% to world coffee production, it is very important in Malaysia; there it is the most important coffee, with an estimated 12 000 ha in 1989, 80% of the total area under coffee. Centres of cultivation in Malaysia are Selangor, Johore, Malacca, Perak and eastern Sabah. In the Philippines about 22 000 ha or 25% of the total area under coffee is liberica coffee, mainly in Luzon. Indonesia produces some 4000 t of liberica coffee annually.
On a dry matter basis liberica coffee beans contain about 0.5-1.8% of caffeine. The average composition per 100 g is: water 11 g, protein 14 g, sucrose and reducing sugars 8 g, cellulose and polysaccharides 42 g, lipids 12 g, chlorogenic acids 7 g, ash 4 g, and caffeine 1.6 g.
The 1000-seed weight with parchment is about 575 g.
An evergreen shrub or tree up to 20 m tall; branchlets glabrous. Leaves opposite; stipules interpetiolar, triangular-ovate to almost truncate, 2-4.5 mm long, obtuse or sometimes acute; petiole 0.8-2 cm long; blade narrowly obovate to obovate or elliptical to broadly elliptical, 14-38 cm × 5.5-20.5 cm, acute to cuneate at base, margin entire, rounded to shortly acuminate at the apex, with domatia situated at the base of the (7-)8-13 lateral veins below. Flowers in axillary clusters, 4-30(-50) per axil, borne in 1-3(-5) congested fascicles, 5-9-merous; peduncle very short or absent; calyx tubular, 1.7-2.5(-3.6) mm long; corolla white, tube 4-13 mm long, lobes contorted to the left in bud, oblong, 8-16 mm × 3-6 mm; stamens attached to the corolla throat; disk annular; ovary inferior, 2-locular with a single ovule in each cell, style exserted, with 2 stigmatic arms. Fruit an oblong-ellipsoid drupe (commonly referred to as "berry"), 1.2-2.2 cm × 0.9-1.6 cm, red or yellow and red streaked or occasionally entirely yellow when mature, with 2 seeds; mesocarp fleshy; endocarp fibrous. Seed (commonly referred to as "bean") 0.7-1.5 cm long, grey-brown-green, with a groove on the inner surface; testa thin, silvery. Seedling with epigeal germination; cotyledons emergent, persistent, leafy, roundish with a wavy margin; hypocotyl slightly elongated; all leaves opposite.
Growth and development
Liberica coffee seeds take about 50 days to germinate. The trees develop, like all coffees, according to the architectural model of Roux, which is characterized by a continuously growing monopodial orthotropic stem with plagiotropic opposite branches. The first fruits are produced 2-3 years after planting out in the field. After 5-6 years the plants are in full bearing. The economic life span is about 25-30 years. Flowering and fruiting may take place throughout the year, but flowering is triggered by heavy showers; the flower buds grow to a certain size and then rest until stimulated by continued water stress and rapid rehydration, resulting in simultaneous blooming. C. liberica is self-incompatible. Fruit maturation takes 10-12 months, depending on the locality.
Other botanical information
(See also under Coffea L.) Botanically seen, C. liberica represents a variable complex of forms that have often been treated as "species" in the past. The forms are generally distinguished by growers and breeders who are aware of the crop and its different habits. It is still uncertain whether excelsa coffee, comprising the former taxa C. dewevrei and C. excelsa , should be regarded as a separate species. For now, it is recognized as a distinct variety, var. dewevrei (De Wild. & T. Durand) Lebrun, distinguished by a 5-6(-8)-merous corolla, tube slightly widened at the throat, lobes usually 2.5-7 mm wide, fruit 12-20 mm × 8-16 mm. Var. liberica has a 6-9-merous corolla, tube distinctly widened at throat, lobes usually 5-10 mm wide, fruit 20-25 mm × 17-21 mm. Moreover the fruit of var. liberica has a thicker, more leathery pericarp and is often more tapered towards the base than that of var. dewevrei .
Liberica coffee occurs in lowland to lower montane rain forest, gallery forest, forest margins and even in open scrub vegetation, up to about 1300 m altitude. In Malaysia plants are reported to thrive up to 1200 m altitude, in the Philippines up to 900 m. It grows well at low elevations under warm, humid conditions, but especially excelsa cultivars are drought-tolerant. Liberica coffee grows best under light shade, on well-drained clayey to sandy soils, but in Malaysia it is generally grown in full sunlight. It does not tolerate waterlogging, but is known for its tolerance of acid and poor soils, and can grow without liming on alluvial muck soils with a pH of about 4.0. In the equatorial lowland tropics liberica coffee performs better than arabica and robusta. It can grow on heavy clays unfavourable to robusta, it is more drought-tolerant and flowers more frequently.
Propagation and planting
Liberica coffee is mainly propagated by seed. Sometimes seedlings are collected from under the trees. Until recently no improved seed was used apart from superficial selection of open-pollinated seedlings. Floating fruits are discarded, others are depulped and dried before sowing. The seeds show recalcitrant storage behaviour, with only 6% of them surviving desiccation to 11.3%. Seeds are sown in seedbeds prepared from alluvial sand, about 1.5 cm deep and 5-8 cm apart or in rows 30 cm apart. Seedlings are planted in polythene bags 8-12 weeks after sowing when they have 2-4 pairs of leaves. They are transplanted into the field when they have developed 6-8 pairs of leaves, which under normal circumstances will be 8-10 months after sowing. The time of transplanting should ideally coincide with the onset of the rainy season. Planting is done in holes of 0.6 m × 0.6 m × 0.6 m and should not be too deep. In Malaysia the recommended planting distance is 2.5 m × 3 m, but 3 m × 3 m is still widely practised. In the Philippines spacings of 4-5 m × 4-5 m are applied. C. liberica seedlings can be used as rootstock for arabica coffee ( C. arabica L.) and robusta coffee ( C. canephora Pierre ex Froehn.); cleft grafting gives 65-75% success. Liberica coffee is sometimes grown in mixed plantations with coconut palm, oil palm and/or bananas. Intercropping with bananas is generally at the expense of an early crop of coffee. Catch cropping has been successful: shallow-rooting crops like gourds, tobacco, chili peppers, long beans and ginger can be planted in between the coffee shrubs when these are still small. Care must be taken that the catch crops are no closer to the coffee than 1 m in the first year and 1.25 m in the second year. Crops that require deep digging for harvesting, such as cassava, are unsuitable.
In Malaysia, liberica coffee is maintained as capped single-stem shrubs about 1.5 m tall by regular pruning, eventually resulting in an umbrella-shaped treelet. Sometimes the multiple-stem system is applied on 2-5 orthotropic capped or uncapped stems.
Highest yields of liberica coffee are obtained without shade, but in practice light shading is applied to protect the plants during periods of water and heat stress. Weeding requires special care, so as not to damage the superficial roots of coffee. Mulching significantly increases yields by improving soil texture, water infiltration and nutrient management. Fertilizer application is often based on soil and foliar analyses. In the Philippines a general recommendation in the absence of soil or foliar analyses is to apply annually an equal amount of NPK fertilizer ranging from 200-450 g for a non-bearing tree to 1 kg of 10:5:20 NPK fertilizer for a bearing tree. Additionally, ammonium sulphate is applied as a top dressing at a rate of 250-300 g/tree per year. The recommended NPK ratio is 7-12-20 for sandy soils and 11-40-5 for clay soils. On peaty soils the presence of copper as a trace element has been found essential.
In Peninsular Malaysia old and unproductive stands are rehabilitated by top-working: this entails regrafting the top of the coffee shrub.
Diseases and pests
Liberica coffee has proved to be susceptible to coffee leaf rust ( Hemileia vastatrix ), although much less than the other coffees. The first sign of attack is the formation of small, circular, yellowish, translucent spots on the leaf, rapidly followed by the production of orange-yellow spores on the underside. In Malaysia half yearly application of Coprantol at 0.1% active ingredient gives protection against coffee leaf rust. Pink disease ( Corticium salmonicolor ) attacks the woody parts of liberica coffee and sometimes causes serious damage. Some Liberica plants are immune to the fungus Ceratocystis fimbriata whereas others are killed instantly; the immune plants contain more polyphenolic compounds.
The beehawk moth ( Cephanodes hylas ) considerably reduced the area under coffee early this century, and is still an important pest in Malaysia. Gardenia trees are an alternative host to the beehawk moth and should not be allowed to grow near coffee fields. The coffee berry borer ( Stephanoderes hampei ) is another serious insect pest; the female beetle bores into the fruits, where the complete life cycle takes place. In Peninsular Malaysia, liberica coffee is much less susceptible (1-5% of the fruits bored) than robusta coffee (16-77%). Endosulfan, one of the few insecticides penetrating the coffee bean and killing the insect larvae, gives protection against coffee berry borer when applied at 0.1% active ingredient. Recent reports from New Caledonia, however, indicate resistance to this insecticide. Therefore, its widespread use may increase the risk of resistance developing in other coffee-growing areas. Generally, liberica coffee is less susceptible to nematodes than robusta coffee, but in Java Pratylenchus coffea once affected about 60% of liberica coffee in six months.
There are two methods of harvesting coffee, i.e. selective picking of the ripe berries and strip picking of whole branches resulting in a mixed harvest of green, ripe and overmature fruits. Coffee growers are said to prefer excelsa cultivars over liberica ones as the fruit is easier to pulp and the flavour of the beans is less bitter. Harvest is generally twice a year.
The weight of dry "green beans" is about (7-)10% of that of fresh fruits. Annual yields of 750-900(-1100) kg/ha of green beans can be obtained from well-maintained holdings but in Malaysia annual yield figures vary between 300 and 700 kg/ha. Improved cultivars have a potential annual yield of 1.7 t/ha and selected clones even 2.1-2.3 t/ha. In Malaysia production peaks in November-February.
Handling after harvest
Coffee fruits can be processed either by the "dry process" or the "wet process". Generally, liberica coffee is processed dry, although the relatively thick fruit pulp would suggest that wet processing is more appropriate.
- The wet process: ripe fruits are pulped within 12-24 hours after harvesting and fermented to degrade the mucilage, washed, carefully dried in the sun (7-10 days) or mechanically (6-20 hours) or a combination of both, and stored as dry (11-12% moisture content) parchment coffee. This process is carried out in coffee factories owned by estates and smallholder cooperative societies, or with small hand-pulpers and basins by individual smallholders.
- The dry process: fruits, usually from strip picking, are dried directly for 3-4 weeks in the sun on platforms or mechanically (2-3 days). Dry-processed coffee is more difficult to store than parchment coffee because of its strong hygroscopic properties.
Liberica coffee fruits present difficulties in pulping because of the large fruit size and the hard fruit skin. However, improvement of planting material in Java early this century through selection gave softer fruits which were easier to pulp. Besides, excelsa cultivars also have softer fruits than liberica cultivars.
Curing of dried parchment coffee - including hulling to remove the parchment, polishing to remove remains of silver skin and grading - takes place in central coffee mills. Dry-processed coffee is treated in a similar manner, but requires a different type of huller. The clean coffee is graded according to international standards of size and shape of beans, colour and percentage defects (broken beans, stones, husks). The clean green coffee is exported in bags of 60-70 kg, and can be stored under dry and cool conditions for 1-2 years without loss of quality. The final stage of coffee processing - blending, roasting and packaging as whole beans or ground coffee - always takes place close to the consumer market to assure optimum quality.
Spontaneous populations of C. liberica can be found in humid tropical lowland forests in West and Central Africa. The collected material is preserved in field collections in Ivory Coast. In Java the Indonesian Coffee and Cocoa Research Institute (ICCRI) maintains a Coffea germplasm collection of some 2000 accessions, including liberica coffee.
The genetic basis of cultivated liberica coffee in Peninsular Malaysia is narrow, but variations in yield, fruit and bean size among individual plants and progenies are significant. In 1992 the Malaysian Agricultural Research and Development Institute (MARDI) released improved seed from a polyclonal coffee seed garden under the name "MKL 1". The selection of superior clones of liberica coffee continues. In Indonesia in the past several breeding experiments with C. liberica and C. arabica resulted in offspring with arabica-like beans and promising resistance to coffee leaf rust. However, plants had to be propagated by grafting, percentage empty seeds was high, and yields were disappointing. "Kalimas" and "Kawisari" are natural hybrids of C. arabica and C. liberica . Several other breeding experiments involving C. liberica and C. canephora , C. congensis Froehner, C. eugenioides S. Moore and C. stenophylla G. Don have been performed recently, notably by the "Institut de recherche pour le développement" (IRD, formerly ORSTOM), but no new cultivars have resulted so far.
Because of its bitter taste, the market share of liberica coffee will remain low. The excelsa cultivars are superior in this respect. First results from experiments carried out by MARDI to develop superior cultivars are positive: several promising clones with higher yield potential have been identified.
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M.S.M. Sosef & E. Boer