Passiflora edulis (PROSEA)
Passiflora edulis Sims
- Protologue: Bot. Mag. 45: 1989 (1818).
- Family: Passifloraceae
- Chromosome number: 2n= 18
- Passionfruit, granadilla (En)
- Grenadille (Fr)
- Indonesia: buah negeri (Java), pasi (Sunda), konyal
- Malaysia: buah susu, markisa
- Philippines: pasionaria (Tagalog), maraflora (Ilokano)
- Laos: linmangkon, not
- Thailand: linmangkon (Bangkok), benchawan (Chiang Mai)
- Vietnam: chùm bap.
Origin and geographical distribution
Passionfruit is a native of southern Brazil where it grows on the edges of rain forests. There are two distinct forms: forma edulis, the purple passionfruit, occurs in cool environments at higher altitudes, whereas forma flavicarpa, the yellow passionfruit, is at home in the tropical lowlands. The two types were distributed throughout the tropics and subtropics via Europe and Australia during the 19th Century. In South-East Asia passionfruit is mainly a home garden crop.
The fruit may be eaten fresh, but mostly the pulp is extracted and preserved by heating or cooling. The juice has a unique and intense flavour and high acidity which makes it a natural concentrate. When sweetened and diluted it is very palatable and blends well with other fruit juices. Typical processed products are ice cream, sherbet, nectar, juices, concentrate, squash, jams and jellies.
Production and international trade
Passionfruit is a small crop; the estimated commercial area in a dozen major producing countries is only about 4500 ha. Roughly 3000 ha is in South America, mainly in Brazil, Peru and Ecuador. Sri Lanka is by far the most important producer in Asia with 800 ha. Australasia has about 550 ha, including Papua New Guinea (80 ha) and Fiji (70 ha). A cooperative in the Philippines grows 200 ha of passionfruit and plans to expand.
The commercial crop is largely converted into juice, about half of which - equivalent to some 25 000 t fresh fruit - enters world trade. Export of fresh fruit is in the order of 1000 t and includes small quantities from Thailand and the Philippines. In the later 1980s processors in Queensland paid US$ 20-30 per 100 kg fruit. The price in the fresh fruit market showed extreme fluctuations; in Queensland growers were getting US$ 1-4 per kg, depending on the season.
The fruit shell is about 45% of the fresh weight; 100 g of the edible pulp contains: water 69-80 g, protein 2.3 g, fat 2.0 g (almost all in the seed), carbohydrates 16 g, fibre 3.5 g, Ca 10 mg, Fe 1.0 mg, vitamin A 20 IU, trace thiamine, riboflavin 0.1 mg, nicotinamide 1.5 mg and vitamin C 20 mg. The energy value amounts to 385 kJ/100 g.
- A vigorous perennial but short-lived semi-woody vine, up to 15 m long. Stems glabrous, grooved, green. Tendrils axillary, spirally coiled, terete, longer than the leaves.
- Leaves with stipules and petioles; stipules lanceolate, 1 cm long; petiole 2-5 cm long, glabrous, grooved above, 2 circular glands at top; blades unlobed when young, later palmately 3-lobed, cordate at base; lobes ovate-oblong, 10-15 cm x 12-25 cm, acuminate, margin with curved teeth that are glandular tipped.
- Flowers solitary, axillary, fragrant, showy, 7.5-10 cm in diameter; peduncle triangular, 2-5 cm long, near the apex with 3 leafy, ovate to lanceolate bracts; calyx tubular at base, lobes 5, spreading, reflexed, yellow-green below, white above, margins with up to 4 glands, apex with a thornlike appendage; petals 5, free, white and thin, alternating with calyx lobes; corona with 2 outer rows of wavy, radiating threads, 2-3 cm long, white with purple base, and 3 inner rows of short purple-tipped papillae; stamens 5, filaments united into a tube round the gynophore for about 1 cm and then widely parted for 1 cm, anthers large, versatile, 2-celled, transverse, pale yellow, hanging downward; ovary on gynophore, ovoid, 1-locular with 3 parietal placentas, styles 3, horizontal, clavate, with longitudinal furrow, 1 cm long, stigmas reniform or cordiform, 0.5 cm in diameter.
- Fruit a globose or ovoid berry, 4-12 cm × 4-7 cm, deep purple or canary yellow; exocarp hard and thin, mesocarp greenish, endocarp white.
- Seeds many, attached to peg-like funiculi on the ovary wall, surrounded by yellowish aromatic pulpy/juicy edible arils; testa hard, black, 3-toothed at base.
Growth and development
Seeds lose their viability within a few weeks. Germination takes 2-4 weeks; the seedlings grow slowly and require 3-4 months to reach the transplanting height of 20-25 cm. Within 5-7 weeks after transplanting, each plant will have up to four healthy laterals. From then on the vine grows very rapidly; the first flowers are produced 5-7 months after transplanting when the vine can be 10-15 m long.
Flower buds emerge sequentially on the new shoots. They take 40-46 days to anthesis; the purple fruit matures 60-90 days later, the yellow fruit after 60-70 days. Initial fruit set is usually excellent and when the shoot bears some 9 fruits, extension growth slows down and both fruit set and flower bud formation tend to fail, although vigorous young shoots may bear more than 20 fruits. Sequential flowering during a flush results in fruit maturing over a period of 2-3 months. Thus flowering and fruiting are closely linked to shoot growth. As in many vines, light is the essential factor for flowering and in passionfruit this is particularly true for floral development and fruit set. That is why training and pruning are important to ensure adequate exposure of the shoots. In a monsoon climate most flowers are produced on the flush occurring at the end of the rainy season. Depending on the climate there may be 1-3 harvest peaks (purple passionfruit) or a single, often very long harvest season (more common with the yellow passionfruit).
Flowers open shortly after sunrise and remain open until mid-morning the next day, but the stigma is receptive only on the first day. The purple passionfruit is self-compatible, setting well if selfed, but the yellow passionfruit often requires cross-pollination. Bees are the main pollinators; when and where they are not sufficiently active, hand pollination can be practised. The fruit follows a smooth sigmoid growth curve and attains its maximum diameter in about 3 weeks. The juice content is negligible until shortly before harvest.
Other botanical information
In P. edulis two forms are distinguished:
- f. edulis : the purple passionfruit with deep purple fruits 4-5 cm in diameter, with green tendrils and leaves. This is the most common form, said to have the best flavour.
- f. flavicarpa Degener: the yellow passionfruit with canary-yellow fruits 6-12 cm × 4-7 cm and reddish-purple tinged tendrils and leaves; larger, more showy flowers with deeper purple corona and more vigorous growth.
In most countries cultivars of the yellow passionfruit are commonly grown, such as "Waimanalo Selection", "Yee Selection" and "Noel's Special" (Hawaii) and "Mirim" or "Hawaiiana" (South America). Purple passionfruit dominates in southern and eastern Africa and in New Zealand ("Bali Hai"); in Australia cultivars are planted which are hybrids of the two forms: "E 23", "Purple Gold", "Lacey" and "Black Beauty".
Of the 400 known species of Passiflora L. about 50-60 bear edible fruits. In South-East Asia 5 non-edible species are endemic; about 13 edible species have been introduced. In addition to P. edulis, P. quadrangularis L. is important. Some minor introduced species are described in the chapter on minor edible fruits and nuts. Frequently, Passiflora plants are cultivated as ornamentals for their showy flowers.
The yellow passionfruit grows best at altitudes of 0-800 m; the purple passionfruit forms virtually no flowers below 1000 m and should be grown at altitudes of 1200-2000 m. The mature purple passionfruit tolerates light frosts and can be grown in the subtropics, as in Australia and New Zealand. Both crops grow on a wide range of soils; heavy clay soils have to be drained and very sandy ones need heavy manuring. A pH of 6-8 is preferred. In South-East Asia the crops are grown in areas with 2000-3000 mm annual rainfall, but especially the purple passionfruit grows well on as little as 900 mm in Africa and Australia, provided the rainfall is well distributed.
The vines require sheltered locations without extreme temperatures: below 20°C pollen does not germinate and at 18-15°C both growth and flowering are set back, whereas temperatures above 30-32°C stimulate growth at the expense of flowering and fruit set. These critical temperatures were established for hybrid cultivars in Australia.
Propagation and planting
Passionfruit is generally propagated from seed, although cuttings and grafting can be used. Seed viability declines rapidly after 2 months. Storage at a relative humidity of around 10% in sealed packages in air-conditioned rooms maintains a high germination rate (> 70%) for up to 12 months. Seed should be rubbed clean of pulp and dried in the shade. Nowadays seedlings are often raised in polythene bags, 15 cm wide and 25 cm deep. Three seeds per bag are sown at a depth of 1 cm and thinned to leave one after two months.
Cuttings are set in steam-sterilized coarse sand and later transplanted into bags or a nursery bed. In trials with purple passionfruit, terminal cuttings with 3-4 nodes and one or two leaves gave better rooting than other types of cuttings. Application of 3000 mg/l indole butyric acid (the optimum rate) improved and speeded up rooting. Grafting is often employed to control diseases. Yellow passionfruit is used as resistant rootstock although other Passiflora species, in particular P. caerulea L., show much greater resistance to Phytophthora root rot and Fusarium collar rot. Moreover, P. caerulea is tolerant of rootknot nematode and to exposure to -1.5°C; it can be propagated from leaf and stem cuttings and is compatible with P. edulis. Wedge and whip grafts on seedling rootstocks - sometimes on rooted cuttings - are used. Micro-propagation using axillary buds gives good results.
In most parts of South-East Asia passionfruit is a backyard crop and seeds are often sown at stake. Support is essential even under such conditions. Commercial plantations adopt a row spacing of 1.2-1.8 m and a within-row spacing of 3 m. This gives 1851-2777 plants/ha. Planting holes of 45 cm × 45 cm × 45 cm should be filled with topsoil mixed with up to 10 kg compost or manure and about 120 g double superphosphate where P is required. Transplanting is done at the start of the rainy season.
Early growth of passionfruit is slow and regular weeding is essential. Mulching along the rows or around the base of the plants greatly facilitates weed control and protects the roots. Being a short-term perennial, passionfruit is an ideal intercrop during the establishment period of crops such as oil palm and rubber.
Elaborate trellises have been used in Australia and South Africa but in East Africa, especially at closer spacing, a single wire trellis has been found to be as good. A 14-gauge galvanized wire is tightly stretched along the tops of hardwood posts 15 cm in diameter and 3 m long, dug in to a depth of 0.6 m; these posts are spaced 8 m apart. The trellis should be erected when the field is planted so that the main shoot and one vigorous lateral can be tied to the wire with a string. If laterals do not emerge in time, they can be forced to leaf out by pinching off the shoot tip. When the vines reach the wire they are trained in opposite directions along it. All laterals below the wire are pruned off. Laterals emerging along the wire are allowed to hang down freely; they are the secondary shoots branching into tertiary shoots. Secondary and higher order shoots are the fruiting wood which has to be thinned and rejuvenated by pruning.
Side dressing is practised with 50 kg N per ha 4 weeks after transplanting and every 12 months after that.
Diseases and pests
The most important disease in the region and worldwide is brown spot (Alternaria passiflorae and A. plagiata) on leaves, vines and fruits. Phytophthora blight (Phytophthora nicotianae var. parasitica) causes the wilting of shoot tips and crown rot, particularly where water stagnates occasionally. Septoria spot, caused by the fungus Septoria passiflorae, causes extensive spotting of leaf and fruit, and occasionally of the stem. These three fungal diseases can be controlled by fortnightly sprays of copper fungicides or Ridomil. Pruning to open up the canopy for fungicide penetration is also essential. Yellow passionfruit and its hybrids are more tolerant of the diseases. Fusarium wilt is caused by the soilborne fungus Fusarium oxysporum f. sp. passiflorae; the shoots wilt, followed by a complete collapse of the plant. Grafting to wilt-resistant yellow passionfruit rootstocks is the most practical way of control. Damping- off caused by Rhizoctonia solani and Pythium spp. can be a problem in nurseries and soils should be sterilized.
A number of virus diseases has been reported; the most widespread and serious one is woodiness. It is spread by aphids (Aphis gossypii, Myzus persicae) and pruning knives. Other virus diseases are ringspot from Ivory Coast, which is similar to woodiness and spread by aphids and passionfruit mosaic (PFMV-K and PFMV-MU) reported in Sarawak and other areas, which is spread by aphids and pruning knives. The most practical control is to use clean planting material, clean pruning tools and resistant hybrids, or rootstocks of yellow passionfruit.
Nematodes, especially the rootknot nematodes (Meloidogyne incognita, M. javanica and M. arenaria), are the most serious pest. Practical control measures are crop rotation and the use of tolerant rootstocks. The cocoa mirid Helopeltis clavifer, the passion vine bug Leptoglossus australis and the green vegetable bug Nezara viridula suck and pierce leaves and young fruits; these, together with the leaf-eating caterpillars of Tiracola plagiata, are minor pests.
Fruit flies include the oriental fruit fly (Dacus dorsalis), the melon fly (D. cucurbitae), the Mediterranean fruit fly (Ceratitis capitata) and the Queensland fruit fly (D. tryoni). Pierced young fruit shrivels and falls; later injuries cause damage which lowers the grade. Spraying insecticides may be essential if destruction of infested fruit and the use of baits do not adequately check the pest to safeguard fresh fruit export markets.
Mealy bugs (Planococcus citri) are usually controlled by their natural enemies (Cryptolaemus montrouzieri). The same applies to scales and mites which incidentally do much damage: the red scale (Aonidiella aurantii) and soft brown scale (Coccus hesperidum) as well as the red spider mite (Brevipalpus papayensis) and the passion vine mite (Brevipalpus phoenicis).
Fruit drops to the ground when fully mature. It is collected once or twice per week; at this stage it looks shrivelled and unattractive. For fresh fruit markets, especially the export market, fruit is picked after full colour development when the whole fruit is purple or canary yellow, but before shrivelling and drying set in.
A plantation is usually cropped for 3 years; of the total crop, roughly 50% is produced in the first year, 35% in the second, and 15% in the third year. The sharp decline in yield level, which is even more marked in areas with disease problems, is the main reason to replant fields after the second or third crop. Average yields amount to 10-15 t/ha per year for the purple and 20-25 t/ha per year for the yellow passionfruit. Much higher yields are possible; yields as high as 50 t/ha per year for purple passionfruit have been reported from Kenya.
Handling after harvest
Fruit for processing is delivered to the factory where the pulp is extracted and the juice is expelled by centrifugation. Passionfruit juice can be produced and bottled by small factories at village level. The aroma and flavour of the juice are sensitive to heat; preservation by freezing is therefore preferred. Where pasteurization by heat is necessary, it should be done by agitation in the can (spin pasteurization).
Fresh fruit can be stored at 5-7°C, 85-90% relative humidity, for 3 weeks; there is a weight loss of 32% when fruit is removed from such storage. In Kenya standards have been laid down for fresh fruit for export, including a diameter size larger than 25 mm, and a smooth, clean, unblemished and freshly coloured skin. The fruit is packed in a single layer in rigid containers with ventilation slots. The containers are lined with tissue paper and on top of the fruit comes a layer of padding material to ensure a firm pack.
Large germplasm collections are kept in Queensland (Australia), Hawaii (United States) and Brazil. A few lines of yellow passionfruit are at the University of Technology, Lae (Papua New Guinea).
The major breeding objective is to incorporate resistance to nematodes and diseases such as Fusarium wilt and woodiness virus. Most of these traits come from the yellow passionfruit; in Queensland the purple passionfruit has been completely replaced by yellow/purple hybrids. P. caerulea, which is more tolerant of many pests, diseases and low temperature, has not yet featured in any breeding programme.
Passionfruit has a history of ups and downs in many parts of the world. Easy propagation and good early yields facilitate expansion of production at such a pace that markets are upset. The other threat is that diseases catch up with the expanding crop and become ruinous before the growers have come to grips with them.
In spite of this volatile history, the prospects for passionfruit in South-East Asia appear to be favourable: the large home market provides a solid basis for expansion, and more resistant cultivars and improved crop protection should go a long way towards maintaining crop health. The possibilities for exporting fresh fruit pulp or juice to countries such as Japan and South Korea, as well as to Europe and America, should also be explored.
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