PASSIONFRUIT AND GIANT GRANADILLA
Passiflora spp., family PassifloraceaeThe passionfruit is a perennial, vigorous, climbing, woody vine that produces an edible round or ovoid fruit with many small seeds. The fruit is eaten alone or in fruit salads, sherbets, ice cream, jams, and in cool drinks.
Commercial production of passionfruit in the United States is limited to Hawaii. A few plants are grown in dooryards in southern Florida and commercial planting in that area is recommended (Morton 1967). No production figures are available, although Morton (1967) stated that in 1958, 1,200 acres was devoted to production of yellow passionfruit in Hawaii (see below), and the industry was firmly established on a satisfactory economic level. The volume of production of this crop is small compared to most other fruit crops. Worldwide, the greatest volume of production is in Brazil, but the fruit is also produced in Colombia, Venezuela, Australia, New Zealand, Kenya, South Africa, India, and Indonesia.
Passionfruit is known in Hawaii as lilikoi, in Australia as golden passionfruit, in Brazil as maracuja peroba, and in South Africa as yellow granadilla.
There are about 300 species of Passiflora, most of which are native to the warmer moist regions of the Americas, and many produce edible fruit, but only two species are cultivated - P. edulis Sims and P. quadrangularis L.
There are two recognized forms of P. edulis. The purple passionfruit, f. edulis, is the normal form. Its fruit is egg shaped or round, 1 1/2 to 2 1/2 inches in diameter, and purple when ripe. It has the best flavor but does not grow well in the wet lowlands. The yellow passionfruit, P. edulis f. flavicarpa Degener, presumably originated as a mutation from the purple passionfruit (Akamine and Girolami 1959). Its fruit is slightly larger, 2 to 2 l/2 inches in diameter, and deep yellow when ripe. The crop is suited to the lowlands of the tropics, but the fruit is more acid than that of the purple passionfruit. There are various cultivars of the yellow passionfruit.
Passiflora quadrangularis L., the giant granadilla, is also cultivated to a limited extent in Brazil for local consumption. It grows best in a hot moist climate, and produces a round or oblong, pale-yellow to yellowish- green fruit when ripe, which may reach 6 by 12 inches in size.
Plant:
Cultivation and pollination requirements of both species are similar and will be combined in subsequent remarks. The plants are usually set in rows 10 feet apart with the plants 6 to 10 feet apart in the row. The vines are trained onto a trellis about 7 feet high. They are cut back to the ground each year but send up new runners to produce the next crop. A plant may be productive 4 to 6 years. The crop is usually grown from seeds in the nursery and transplanted to the field 3 to 4 months later when about 12 inches high. No information is available on seed quality in relation to cross-pollination between cultivars, which could influence productivity. Propagation by cuttings is possible, but is usually not practiced. Plants that are started in the fall produce a light crop the next year. If they are started in the spring, they produce a light crop the same year and a good crop the next year (Meurant 1959).
Average yields in Kenya are 15,000 pounds of fruit per acre per year (Purseglove 1968*); however, 40,000 lb/acre of fruit with 35 percent juice content has been produced from choice strains of yellow passionfruit in Hawaii (Morton 1967). Willis (1954) stated that in Australia a yield of 100 bu/acre may be expected the first summer, 12 to 15 months after planting. The relation of pollination to these drastic differences is not given but likely plays an important part.
Inflorescence:
The attractive and fragrant complete flower is 2 to 3 inches in diameter. It is solitary on the vine amongst the large 4- to 6-inch by 5- to 10-inch, three-lobed leaves. It has three bracts, a five-lobed calyx tube, five white spreading petals, a colorful filamentous corona, five strong stamens with large anthers, a triple-branched prominent style, each branch with an enlarged stigma, and a single ovary with several hundred ovules that, when fertilized, form the small seed within the fruit (fig. 141 ).
The passionfruit was named by early missionaries in South America who saw in it the implements of crucifixion, that is, the crown of thorns (corona), the five wounds (five anthers), the nails of the cross (divisions of the pistil), the whips and cords (the tendrils on the vine), and the spear (leaf).
Flowers of the purple passionfruit open at dawn and close about noon. Flowers of the yellow passionfruit open about noon and close at the end of the day. Flowering extends from early spring to late fall. Peak flowering occurs in late spring when one flower can be found per 2 to 5 feet of row (Nishida 1963). Nectar is secreted at the base of the pistil stalk (Akamine et al. 1954). The nectar is relatively rich (50 percent soluble solids).
The style is upright when the flower opens but recurves downward shortly afterwards until each branch is about on a level with the anthers. Shortly before the flower closes, the style returns to its upright position. About an hour is required for each change to occur. In some flowers, the style may remain erect, but such flowers are female-sterile, although their pollen is functional. The most effective time for pollination is after the style has recurved. At this time, the stigma is in the position where it is most likely to be brushed by pollinating insects, and the stigmatic fluid is present to insure adhesion by the pollen grains so the pollen tube growth can start. The stigma is receptive from the time of flower opening to closing (Cox 1957). Pollen is released before the flower opens and before the stigma is receptive. The pollen is not windblown.
[gfx] FIGURE 141.- Longitudinal section of passion fruit flower, x 2.
Pollination Requirements:
The flowers of passionfruit are self-sterile, and some plants are even self-incompatible (Akamine and Girolami 1957). Care must be taken, therefore, in the selection and distribution of compatible clones or cultivars in the field to insure maximum fruit production (Gilmartin 1958). The amount of pollen deposited on the stigma determines the number of seeds set and size of the fruit. The ovule must be pollinated and the seeds developed if juice is to form in the aril (pulp sac) (Knight and Winters 1962, 1963). A fruit can develop as many as 350 seeds. Unless about 100 ovules develop into seeds, the fruit is likely to be "hollow" (light in weight and with little juice). Few fruit develop with fewer than 50 seeds. There is no parthenocarpic set of fruit.
Akamine and Girolami (1959) found that fruit set, numbers of seed, fruit weight, and juice yield correlated with numbers of pollen grains deposited upon the stigma. They concluded that the maximum effect of pollination was not attained with their largest number (1,776) of pollen grains deposited on a stigma. This shows the importance of adequate bee visitation and pollen transfer between flowers within the brief span of time of stigma receptivity for maximum set of fruit.
Pollinators:
Honey bees and carpenter bees (Xylocopa sonorina Smith but known in Hawaii as X. varipuncta Patton) (Nishida 1954, 1958, 1963) are the primary pollinators of passionfruit. Where they are abundant, carpenter bees are doubtless the best pollinating agents because of their larger size. Unfortunately, they are scarce or nonexistent in some areas. Honey bees can be established wherever desired, but they sometimes show preference for more attractive plants than passionfruit. Various species of diptera are sometimes frequent visitors to the flowers, but they are of little value in transferring the pollen between plants. They tend to feed, then rest, without going immediately to the next flower, as the nectar and pollen collecting bees normally do. Other insects in Hawaii never more than occasionally visit the flowers and are of no consideration as pollinators of passionfruit. In Brazil, Trigona spp., and Epicharis spp., are frequent visitors and are unlikely to sting, a factor of concern to some growers. In India, Apis cerana is the primary pollinator (Sriram and Raman 1961).
Honey bees may visit the flowers for nectar or pollen or both. The nectar-collector crawls to the base of the style to the nectary, whereas the pollen-collector crawls busily over the anthers and is soon recognizable by the pellets of pollen in the corbiculae or pollen baskets on its hind legs. The type of food gathered depends upon competing food sources. Satisfactory crops are usually obtained with adequate pollinating agents.
Sriram and Raman (1961) reported that hand pollination of the flowers increased the set of yellow passionfruit by 21 percent over open pollination, whereas it increased set of granadilla by 84 percent.
Nishida (1963) noted that, because pollen is released shortly before the stigma is receptive, some growers feared that complete removal of pollen from the anthers by honey bees might be detrimental to fruit set (Bowers 1953), but experimental results have not confirmed this. If all the pollen is removed from the flowers by honeybees, which is highly unlikely, at least the flower is pollinated first.
Nishida (1 963) also noted that when flowering reached its peak (120 flowers per 200 feet of row), the honey bee population was 35 per 200 feet, or one bee for each four flowers. The number of carpenter bees varied according to their local population.
Pollination Recommendations and Practices:
One of the major problems in passionfruit production is in obtaining a satisfactory set of fruit. This set can only occur when an abundance of pollinators are the flowers and transferring pollen between compatible cultivars. One carpenter bee per 50 feet of row or one honey bee per four blossoms may be sufficient. The optimum number for maximum pollination of passion fruit is unknown. Pope (1935) mentioned large moths and hummingbirds, but in general, moths are not daytime feeders and hummingbirds are never sufficiently prevalent to pollinate crops grown commercially.
Honey bee colonies can be transported and increased wherever and whenever desired. Placement of redwood boards, poplar, or sisal logs can serve as carpenter bee nesting sites and may aid in increasing their number. Logs with carpenter bee nests in them may be transported to a field to establish this insect in a new area.
The yucca plant produces a flower stalk that eventually dries and becomes a choice nesting site for the carpenter bee; therefore, this plant might be grown near passionfruit fields. The larger the planting of passionfruit, the more efficient becomes the activity of the two primary pollinating agents - the carpenter bee and the honey bee - because competing plants are relatively reduced.
On most insect-pollinated crops, and this would appear to include passionfruit, the most satisfactory and surest way to supply ample pollination is by stocking the area with sufficient honey bee colonies. The number per acre of passionfruit might vary enormously with the (generally small) size of the crop and with competing plants.
A fact worth considering would be the interplanting of the purple passionfruit that has flowers open and attractive to bees from dawn to noon, and yellow passionfruit with flowers open from about noon to dusk. This might tend to lure and hold the activity of the bees within the field throughout the day and increase their pollinating effectiveness.
LITERATURE CITED:
AKAMINE, E. K., HAMILTON, R. A., NISHIDA, T., and others.
1954. PASSION FRUIT CULTURE IN HAWAII. Hawaii Agr. Ext. Serv. Cir. 345, 23 pp., rev.______and GIROLAMI, G.
1957. PROBLEMS IN FRUIT SET IN YELLOW PASSION FRUIT. Hawaii Farm Sci. 5: 3-5.______and GIROLAMI, G.
1959. POLLINATION AND FRUIT SET IN THE YELLOW PASSION FRUIT. Hawaii Agr. Expt. Sta. Tech. Bul. 59, 44 pp.BOWERS, F. A. I., JR.
1953. PASSION FRUIT TESTS SHOW PROMISE. Hawaii Farm Sci 2(2): 3, 6, 8.COX, J. E.
1957. FLOWERING AND POLLINATION OF PASSION FRUIT Agr.. GAZ. N.S. Wales, 68: 573-576.GILMARTIN, A. J.
1958. POST-FERTILIZATION SEED AND OVARY DEVELOPMENT IN PASSIFLORA EDULIS SIMS. Trop. Agr. [Trinidad.] 35: 41-58.KNIGHT, R. J., JR., and WINTERS, H. F.
1962. POLLINATION AND FRUIT SET OF YELLOW PASSIONFRUIT IN SOUTHERN FLORIDA. Fla. State Hort. Soc. proc. 75: 412-418.______and WINTERS, H. F.
1963. EFFECTS OF SELFING AND CROSSING IN THE YELLOW PASSIONFRUIT. Fla. State Hort. Soc. Proc. 76: 345347.MEURANT, N.
1959. FAULTY FRUIT-SETTING IN THE PASSION VINE. Queensland Fruit and Vegetable News [ Brisbane] 15: 202.MORTON, J. F.
1967. YELLOW PASSIONFRUIT IDEAL FOR FLORIDA WILLIS, J. M. HOME GARDENS. Fla. State Hort.. Soc. Proc. 80: 320-330.NISHIDA, T.
1954. ENTOMOLOGICAL PROBLEMS OF THE PASSIONFRUIT. Hawaii Farm Sci. 3(1): 1,3,7.______ 1958. POLLINATION OF THE PASSION FRUIT IN HAWAII. Jour. Econ. Ent.. 51: 146-148.
______ 1963. ECOLOGY OF THE POLLINATORS OF PASSION FRUIT. Hawaii Agr. Expt. sta. Tech. Bul. 55,38 pp.
POPE, W. T.
1935. THE EDIBLE PASSIONFRUIT IN HAWAII. Hawaii Agr. Expt. Sta. Bul. 74,22 pp.SRIRAM, T. A., and RAMAN, K. R.
1961. SOME ASPECTS OF FLOWERING AND FRUITING IN YELLOW PASSIONFRUIT AND GRANADILLA. So. Indian Hort.. 9(1-4): 30-37.WILLIS, J. M.
1954. PASSION FRUITS AND GRANADILLAS. Queensland Agr. Jour. 79(4): 205-217.
