_________________________________________________________________

New 2001

E. H. Erickson and A. H. Atmowidjojo

DURIAN

Durio zibethinus Murr., family Bombacaceae

Durian (Durio zibethinus Murr) is a tropical lowland fruit native to Southeast Asia. The oval fruits are larger than coconuts, heavy (several pounds/kilograms), and may reach 10 in (25 cm) in length. They are yellow (when ripe), and covered with a tough inedible rind bearing hexagonal, sharp stubby spines. Pressure will cause the ripe fruit to separate into five locules. Each locule contains a soft, but not juicy, custard like pulp or aril which is very sweet, rich in taste, and filling. The aril surrounds 2-3 seeds about 1.5 in (3.8 cm) long which are easily removed. The color of the aril varies among varieties from white to yellow to pink. Varieties with small seeds and large arils are preferred. Some varieties are seedless. Certain varieties of Durian have a penetrating odor which some consumers consider objectionable or even repulsive, other varieties are almost odorless. The aroma develops as the fruit ripens, reaching its peak 2-3 days after fruit drop which is when the flavor is best. Asians consider the malodorous Durian the ‘King of Fruits’ and a gourmet treat. The aril is eaten fresh, made into jam, dried, frozen, preserved with sugar, fried or lightly baked. It is often added to a variety of foods like rice, ice cream, and dried milk, or fermented to form a condiment. Durian is widely cultivated in the Asian tropics and occasionally in Hawaii and Puerto Rico. Thailand, Malaysia, and Indonesia are the primary producers (Husin and Abidin, 1998; Lee, 1985; Martin, 1980).

Plant:

The evergreen Durian tree has a large attractive pyramidal canopy and may reach 100 ft (30 m) in height. In the wild, trees occur at low frequency in the tropical sub-canopy and may not bear fruit every year. Mature trees may be heavily buttressed. Dark green leaves are thick and leathery with a silver underside. The trees normally bear fruit after 6-10 years. Fruit set is usually during mid- to late summer, but varies throughout Asia (Husin and Abidin, 1998; Martin, 1980).

Durian is propagated by seed. Alternatively, superior clones (cultivars) are produced via grafting buds on seedlings (Bailey and Bailey, 1978; Husin and Abidin, 1998). A number of popular cultivars with improved odor and flavor have been developed in Southeast Asia. Orchards are established with (10-12 m) between trees.

Inflorescence:

Three to fifty blossoms occur in cymose clusters at leafless nodes on mature branches and laterals (Bailey and Bailey, 1978; Husin and Abidin, 1998). Flower color varies from cream to yellow to greenish white. These very large flowers have long spatulate petals 1.2-2.5 in (3-6 cm) and long stamens 0.8-2 in (2-5 cm) (Chin and Phoon, 1982; Husin and Abidin, 1998). The flowers are protogynous and offer ample opportunity for both self- and cross-pollination. Mature anthers hover above the stigma. The Pollen grains are large (80-150 microns) and the sticky pollen is released in clumps (Chin and Phoon, 1982; Salakpetch, et al., 1992). Stigmatic exudate enhances pollination and pollen germination, and may be gathered by some pollinators. The ovary is superior with 5 locules containing a number of ovules. Five nectaries produce 0.1-1.3 ml of nectar per flower (Husin and Abidin, 1998; Lim and Luders, 1998). Stigmata are receptive and pollen is viable1 to 2 days after anthesis (Chin and Phoon, 1982; Salakpetch, et al., 1992)

Durian usually only flowers once annually producing a large number of blossoms in late winter and early spring following a long (1-2 month) dry period. A second period of fruiting may occur in some areas late in the year. Greater numbers of flowers are produced as the length of the dry period increases. Fruit mature 3-4 months after flowering (Husin and Abidin, 1998; Martin, 1980).

Pollination Requirements:

Durian blooms nocturnally beginning in the late evening and peaking at midnight. Early reports of the pollination requirements of Durian are highly variable and broadly conflicting. Self-incompatibility among Durian cultivars ranges from complete to non-existent, but often leads to increased flower and fruit abortion as well as to reduced yield, and seed viability (Lim and Luders, 1998). Unfertilized ovaries abort within 7-10 days.

A number of factors contribute to poor fruit quality/set in Durian. Along with self-incompatibility, these include inadequate pollination, weather, improper crop husbandry, pests and diseases (Lim and Luders, 1998). Reports suggest that less than 1 percent of the self-fertilized flowers set fruit, while fruit set may reach 60 percent following cross-pollination (Lim and Luders, 1998).

Pollination Recommendations and Practices:

Mixed plantings of clones/cultivars is recommended where Durian is cultivated (Lim and Luders, 1998). Cross pollination produces higher quality fruit with higher fruit set while selfing results in higher rates of abortion and malformed fruit. Orchard site selection appears critical as seasonality in weather conditions also influences flowering and the reproductive biology of the species. Site selection is also important in the availability of pollinators.

Pollinators:

Durian is adapted for nocturnal pollinators like bats and moths. However, pollinating insects like bees (Apis dorsata and Trigona sp.) and ants are attracted to the flowers and may also be important (Husin and Abidin, 1998; Lee, 1985; Martin, 1980; Roubik, 1995; Salakpetch, et al., 1992).

LITERATURE CITED:

Bailey, L. H. and Bailey, E. Z. (eds.)

1978. Hortus Third. 1290 pp. Macmillan Publ. Co., Inc., New York, NY.

Chin. H. F., and Phoon, A. C. G.

1982. A Scanning Electron Microscope Study of Flowers of Carambola, Durian and Rambutan. Pertanika. 5(2):234-239.

Husin, A. and Abidin, M. Z.

1998. Durian. In Shaw, P. E., Chan Jr., H. T., and Nagy, S. eds., Tropical and Subtropical Fruits, pp. 261-289. AGSCIENCE, INC., Auburndale, FL.

Lee, D

1985. The Durian A Most Magnificent and Elusive Fruit. Bull. Fairchild Trop. Garden. 40(2):18-27

Martin, F. W.

1980. Durian and Mangosteen. In Nagy, S., and Shaw, P. E., eds Tropical and Subtropical Fruits, pp 401-414. AVI PUBLISHING, INC., WestPort, CN.

Lim, T. K. and Luders, L.

1998. Durian Flowering, Pollination and Incompatibility Studies. Ann. Appl. Biol 132:151-165.

Nakasone, H. Y. and Paull, R. E.

1998. Tropical Fruits. 445 pp. CAB INTERNATIONAL, Wallingford, UK.

Roubik, D. W.

1995. Pollination of Cultivated Plants in the Tropics. Food and Agriculture Organization of the United Nations, Rome. Bull. 118. 198 p.

Salakpetch, S Chandraparnik, S. and Hiranpradit, H.

1992. Pollen Grains and Pollination in Durian, Durio zibethinus Murr. Acta Hort. 321:636-640