Durian

The name "durian" is derived from the Malay word duri (meaning 'thorn'), a reference to the numerous prickly thorns on its rind, combined with the noun-building suffix -an.[6][7] According to the Oxford English Dictionary, the alternate spelling durion was first used in a 1588 translation of The History of the Great and Mighty Kingdom of China and the Situation Thereof by the Spanish explorer Juan González de Mendoza:[6]

There is one, yt is called in the Malaca tongue Durion, and is so good that [...] it doth exceede in savour all others that euer they had seene, or tasted.

Other historical variants include duryoen, duroyen, durean, and dorian.[6] The name of the type species, Durio zibethinus, is derived from Viverra zibetha (the large Indian civet), a mammal known for its odour.[8]

Durio zibethinus, one of the major food crops in Southeast Asia[9]

Durian flowers are usually closed during the daytime.

Durio sensu lato has 30 recognised species.[10] Durio sensu stricto comprises 24 of these species. The 6 additional species included in Durio s.l. are now considered by some to comprise their own genus, Boschia.[11][12] Durio s.s. and Boschia have indistinguishable vegetative characteristics and many shared floral characteristics. The crucial difference between the two is that anther locules open by apical pores in Boschia and by longitudinal slits in Durio s.s.[13] These two genera form a clade that is sister to another genus in the tribe Durioneae, Cullenia. These three genera together form a clade that is characterised by highly modified (mono- and polythecate, as opposed to bithecate) anthers.[11]

The genus Durio is placed by some taxonomists in the family Bombacaceae, or by others in a broadly defined Malvaceae that includes Bombacaceae, and by others in a smaller family of just seven genera Durionaceae.[1][14][15]

Durio is often included in Bombacaceae because of the presence of monothecate anthers, as opposed to the bithecate anthers common to the rest of the mallows (and angiosperms, in general). However, the first studies to examine mallow phylogeny using molecular data found that the tribe Durioneae should be placed in the subfamily Helicteroideae of an expanded Malvaceae. The authors of these studies hypothesise that monothecate anthers have most likely evolved convergently in Durioneae and in the Malvatheca clade (comprising Malvaceae s.l. subfamilies Malvoideae and Bombacoideae).[16][17]

A draft genome analysis of durian indicates it has about 46,000 coding and non-coding genes, among which a class called methionine gamma-lyases – which regulate the odour of organosulfur compounds – may be primarily responsible for the distinct durian odour.[8][18] Genome analysis also indicated that the closest plant relative of durian is cotton.[8][18]

Juvenile durian tree in Malaysia. Mature specimens can grow up to 50 metres (160 feet).

Durian trees are large, growing to 25–50 metres (80–165 feet) in height depending on the species.[10] The leaves are evergreen, elliptic to oblong and 10–18 centimetres (4–7 inches) long. The flowers are produced in three to thirty clusters together on large branches and directly on the trunk with each flower having a calyx (sepals) and five (rarely four or six) petals. Durian trees have one or two flowering and fruiting periods per year, although the timing varies depending on the species, cultivars, and localities. A typical durian tree can bear fruit after four or five years. The durian fruit can hang from any branch, and matures roughly three months after pollination. The fruit can grow up to 30 cm (12 in) long and 15 cm (6 in) in diameter, and typically weighs one to three kilograms (2 to 7 lb).[10] Its shape ranges from oblong to round, the colour of its husk green to brown, and its flesh pale-yellow to red, depending on the species.[10] Among the thirty known species of Durio, nine of them have been identified as producing edible fruits: D. zibethinus, D. dulcis, D. grandiflorus, D. graveolens, D. kutejensis, Durio lowianus, D. macrantha, D. oxleyanus and D. testudinarius.[19] The fruit of many species has never been collected or properly examined, however, so other species may have edible fruit.[10] The durian is somewhat similar in appearance to the jackfruit, an unrelated species.

D. zibethinus is the only species commercially cultivated on a large scale and available outside of its native region. Since this species is open-pollinated, it shows considerable diversity in fruit colour and odour, size of flesh and seed, and tree phenology. In the species name, zibethinus refers to the Indian civet, Viverra zibetha. There is disagreement over whether this name, bestowed by Linnaeus, refers to civets being so fond of the durian that the fruit was used as bait to entrap them, or to the durian smelling like the civet.[20]

Durian flowers are large and feathery with copious nectar, and give off a heavy, sour, and buttery odour. These features are typical of flowers pollinated by certain species of bats that eat nectar and pollen.[21] According to research conducted in Malaysia in the 1970s, durians were pollinated almost exclusively by cave fruit bats (Eonycteris spelaea);[10] however, a 1996 study indicated two species, D. grandiflorus and D. oblongus, were pollinated by spiderhunters (Nectariniidae) and another species, D. kutejensis, was pollinated by giant honey bees and birds as well as bats.[22]

Some scientists have hypothesised that the development of monothecate anthers and larger flowers (compared to those of the remaining genera in Durioneae) in the clade consisting of Durio, Boschia, and Cullenia was in conjunction with a transition from beetle pollination to vertebrate pollination.[12]

Cultivars

Different cultivars of durian often have distinct colours. D101 (right) has rich yellow flesh, clearly distinguishable from another variety (left).

Over the centuries, numerous durian cultivars, propagated by vegetative clones, have arisen in Southeast Asia. They used to be grown with mixed results from seeds of trees bearing superior quality fruit, but now are propagated by layering, marcotting, or more commonly, by grafting, including bud, veneer, wedge, whip or U-grafting onto seedlings of randomly selected rootstocks. Different cultivars may be distinguished to some extent by variations in the fruit shape, such as the shape of the spines.[10] Durian consumers express preferences for specific cultivars, which fetch higher prices in the market.[23]

Malaysian varieties

The Malaysian Ministry of Agriculture and Agro-Based Industry started to register varieties of durian in 1934, and now maintains a list of registered varieties, where each cultivar is assigned a common name and a code number starting with "D". These codes are widely used through South-East Asia, and as of 2021, there are over 200 registered varieties.[24] Many superior cultivars have been identified through competitions held at the annual Malaysian Agriculture, Horticulture, and Agrotourism Show. There are 13 common Malaysian varieties having favourable qualities of colour, texture, odour, taste, high yield, and resistance against various diseases.[25]

Musang King, the most popular variety of durian in Malaysia

Musang King (D197) is the most popular durian breed from Malaysia, rendered in Chinese as "Mao Shan Wang" (猫山王), which is usually the priciest of all cultivars. The origin of the name "Musang King" dates back to the 80s, when a man named Tan Lai Fook from Raub, Pahang stumbled upon a durian tree in Gua Musang, Kelantan. He brought the tree branch back to Raub for grafting, and this new breed attracted other cultivators. The cultivar was named after Gua Musang, its place of origin, while the Chinese name references the palm civet, the Malay meaning of musang.[26] Musang King is known for its bright yellow flesh and is like a more potent or enhanced version of the D24.[27] Musang King is also the preferred cultivar in Singapore and Vietnam.[27]

Other popular cultivars in Malaysia include:

• "D24" (Sultan), a popular variety known for its bittersweet taste
• "XO", which has a pale colour, thick flesh with a tinge of alcoholic fermentation
• "Tekka" (from Chinese 竹跤; Hokkien POJ: tek-kha) which has a distinctive yellowish core in the inner stem
• "D168" (IOI), which has a round shape, medium size, green and yellow outer skin colour, and has flesh easy to dislodge. The flesh is medium-thick, solid, yellow in colour, and sweet.[28]
• "Red Prawn" (Udang Merah, D175), found in the states of Pahang and Johor.[29][30] The fruit is medium-sized with oval shape, brownish green skin having short thorns. The flesh is thick, not solid, yellow-coloured, and has a sweet taste.[25]

Indonesian varieties

Local durian in Cigudeg, Bogor, West Java, Indonesia

Indonesia has more than 103 varieties of durian. The most cultivated species is Durio zibethinus.[31] Notable varieties are Sukun durian (Central Java), sitokong (Betawi), sijapang (Betawi), Simas (Bogor), Sunan (Jepara), si dodol, and si hijau (South Kalimantan)[31] and Petruk (Jepara,[32] Central Java).[31]

A durian vendor in Malaysia

Durian cultivation thrives in tropical areas, ceasing growth when average daily temperatures fall below 22°C (72°F). The fruit is native to Southeast Asia and is commonly found in countries like Malaysia, Thailand, Indonesia, and the Philippines. Durian is often called the “king of fruits” in Southeast Asia due to its popularity and rich nutritional profile.

D. zibethinus is not grown in Brunei because consumers there prefer other species such as D. graveolens, D. kutejensis, and D. oxleyanus. These species are commonly distributed in Brunei, and together with other species like D. testudinarius and D. dulcis constitute a genetically diverse crop source.[36]

Although the durian is not native to Thailand, Thailand is ranked the world's number one exporter of durian, producing around 700,000 tonnes of durian per year, 400,000 tonnes of which are exported to mainland China and Hong Kong.[37] Malaysia and Indonesia follow, both producing about 265,000 tonnes each. Of this, Malaysia exported 35,000 tonnes in 1999.[38] Chantaburi in Thailand holds the World Durian Festival in early May each year. This single province is responsible for half of the durian production of Thailand.[39][40] The Davao Region is the top producer of the fruit in the Philippines, producing 60% of the country's total.[41] The Kadayawan Durian Festival is held in conjunction with the Kadayawan Festival, an annual celebration in Davao City, featuring durians and other fruits.[42][43]

Durian was introduced into Australia in the early 1960s and clonal material was first introduced in 1975. Over thirty clones of D. zibethinus and six other Durio species have been subsequently introduced into Australia.[44] China is the major importer, purchasing 65,000 tonnes in 1999, followed by Singapore with 40,000 tonnes and Taiwan with 5,000 tonnes. In the same year, the United States imported 2,000 tonnes, mostly frozen, and the European Community imported 500 tonnes.[38] Due to the increasing popularity of durian in China, the price had risen up to 20 times over in four years, in a market that was worth nearly £400m in 2018. Malaysia negotiated a deal with China to export the whole fruit frozen for the first time to China starting in 2019, previously only Thailand was permitted to export the whole fruit to China.[45] In 2021, exports of durians to China have increased to 821,500 tonnes which was 4 times compared to 2017, and a 42.7 percent increase from the year before. The large majority of that was sourced from Thailand where China purchased at least US$3.4 billion worth or 90 percent of Thailand's fresh durian exports in that year, according to the Thai Ministry of Commerce.[46][47]

The durian is a seasonal fruit, unlike some other non-seasonal tropical fruits such as the papaya which are available throughout the year. In peninsular Malaysia and Singapore, the season for durians is typically from June to August, coinciding with that of the mangosteen.[10]

Prices of durians are high due to postharvest changes and having a short shelf life in normal temperatures.[48] In Singapore in 2007, the strong demand for high quality cultivars such as the D24 (Sultan), and Musang King (Mao Shan Wang) resulted in high retail prices.[23] The edible portion of the fruit, known as the aril and usually referred to as the "flesh" or "pulp", only accounts for about 15–30% of the mass of the entire fruit.[49] By 2018, Musang King farmers saw very large increases in the prices they received, making the fruit far more lucrative than palm oil or rubber. This led to an increase in durian plantation.[45]

Sign informing that the durian fruit is not allowed inside Singapore's Mass Rapid Transit

Sliced deep-fried durian in packages at a market in Thailand

The unusual flavour and odour of the fruit have prompted many people to express diverse and passionate views ranging from deep appreciation to intense disgust.[3][50][51] Writing in 1856, the British naturalist Alfred Russel Wallace provided a much-quoted description of the flavour of the durian:

The five cells are silky-white within, and are filled with a mass of firm, cream-coloured pulp, containing about three seeds each. This pulp is the edible part, and its consistence and flavour are indescribable. A rich custard highly flavoured with almonds gives the best general idea of it, but there are occasional wafts of flavour that call to mind cream-cheese, onion-sauce, sherry-wine, and other incongruous dishes. Then there is a rich glutinous smoothness in the pulp which nothing else possesses, but which adds to its delicacy. It is neither acidic nor sweet nor juicy; yet it wants neither of these qualities, for it is in itself perfect. It produces no nausea or other bad effect, and the more you eat of it the less you feel inclined to stop. In fact, to eat Durians is a new sensation worth a voyage to the East to experience. ... as producing a food of the most exquisite flavour it is unsurpassed.[52]^[a]

Wallace described himself as being at first reluctant to try it because of the aroma, "but in Borneo I found a ripe fruit on the ground, and, eating it out of doors, I at once became a confirmed Durian eater".[53] He cited one traveller from 1599:^[b] "it is of such an excellent taste that it surpasses in flavour all other fruits of the world, according to those who have tasted it."[53] He cites another writer: "To those not used to it, it seems at first to smell like rotten onions, but immediately after they have tasted it they prefer it to all other food. The natives give it honourable titles, exalt it, and make verses on it."[53]

While Wallace cautions that "the smell of the ripe fruit is certainly at first disagreeable", later descriptions by Westerners are more graphic in detail. Novelist Anthony Burgess writes that eating durian is "like eating sweet raspberry blancmange in the lavatory".[54] Travel and food writer Richard Sterling says:

 its odor is best described as pig-excrement, turpentine and onions, garnished with a gym sock. It can be smelled from yards away. Despite its great local popularity, the raw fruit is forbidden from some establishments such as hotels, subways and airports, including public transportation in Southeast Asia.[55]

Other comparisons have been made with the civet, sewage, stale vomit, skunk spray and used surgical swabs.[50] The wide range of descriptions for the odour of durian may have a great deal to do with the variability of durian odour itself.[8][56] Durians from different species or clones can have significantly different aromas; for example, red durian (D. dulcis) has a deep caramel flavour with a turpentine odour while red-fleshed durian (D. graveolens) emits a fragrance of roasted almonds.[3] Among the varieties of D. zibethinus, Thai varieties are sweeter in flavour and less odorous than Malay ones.[10] The degree of ripeness has an effect on the flavour as well.[10]

In 2019, researchers from the Technical University of Munich identified ethanethiol and its derivatives as a reason for its fetid smell. However, the biochemical pathway by which the plant produces ethanethiol remained unclear such as the enzyme that releases ethanethiol.[57]

The fruit's strong smell led to its ban from the subway in Singapore; it is not used in many hotels because of its pungency.[58]

The origin of the durian is thought to be in the region of Borneo and Sumatra, with wild trees in the Malay peninsula, and orchards commonly cultivated in a wide region from India to New Guinea.[3] Four hundred years ago, it was traded across present-day Myanmar, and was actively cultivated especially in Thailand and South Vietnam.[3]

The earliest known European reference to the durian is the record of Niccolò de' Conti, who travelled to Southeast Asia in the 15th century.[71] Translated from the Latin in which Poggio Bracciolini recorded de Conti's travels: "They [people of Sumatra] have a green fruit which they call durian, as big as a watermelon. Inside there are five things like elongated oranges, and resembling thick butter, with a combination of flavours."[72] The Portuguese physician Garcia de Orta described durians in Colóquios dos simples e drogas da India published in 1563. In 1741, Herbarium Amboinense by the German botanist Georg Eberhard Rumphius was published, providing the most detailed and accurate account of durians for over a century. The genus Durio has a complex taxonomy that has seen the subtraction and addition of many species since it was created by Rumphius.[19] During the early stages of its taxonomical study, there was some confusion between durian and the soursop (Annona muricata), for both of these species had thorny green fruit.[73] The Malay name for the soursop is durian Belanda, meaning Dutch durian.[74] In the 18th century, Johann Anton Weinmann considered the durian to belong to Castaneae as its fruit was similar to the horse chestnut.[73]

Michał Boym, a Jesuit missionary to China, provided a 1655 report on durian to European scholars.

Durio zibethinus. Chromolithograph by Hoola Van Nooten, circa 1863

D. zibethinus was introduced into Ceylon by the Portuguese in the 16th century and was reintroduced many times later. It has been planted in the Americas but confined to botanical gardens. The first seedlings were sent from the Royal Botanic Gardens, Kew, to Auguste Saint-Arroman of Dominica in 1884.[75]

In Southeast Asia, the durian has been cultivated for centuries at the village level, probably since the late 18th century, and commercially since the mid-20th century.[3][10] In My Tropic Isle, Australian author and naturalist Edmund James Banfield tells how, in the early 20th century, a friend in Singapore sent him a durian seed, which he planted and cared for on his tropical island off the north coast of Queensland.[76]

In 1949, the British botanist E. J. H. Corner published The Durian Theory, or the Origin of the Modern Tree. His theory was that endozoochory (the enticement of animals to transport seeds in their stomach) arose before any other method of seed dispersal, and that primitive ancestors of Durio species were the earliest practitioners of that dispersal method, in particular red durian (D. dulcis) exemplifying the primitive fruit of flowering plants. However, in more recent circumscriptions of Durioneae, the tribe into which Durio and its sister taxa fall, fleshy arils and spiny fruits are derived within the clade. Some genera possess these characters, but others do not. The most recent molecular evidence (on which the most recent, well-supported circumscription of Durioneae is based) therefore refutes Corner's Durian Theory.[12]

Since the early 1990s, the domestic and international demand for durian in the Association of Southeast Asian Nations (ASEAN) region has increased significantly, partly due to the increasing affluence of Southeast Asia.[10] In the early 2020s a Durian craze in China led to a large increase in international trade of the fruit.[77]

The high demand for durians in China has prompted a shift in Malaysia from small-scale durian orchards to large-scale industrial operations. Forests are cleared to make way for large durian plantations, compounding an existing deforestation problem caused by the cultivation of oil palms.[95] Animal species such as the small flying fox, which pollinates durian trees, and the Malayan tiger are endangered by the increasing deforestation of their habitats.[95][96] In the Gua Musang District, the state government approved the conversion of 40 km² (10,000 acres) of forestry, including indigenous lands of the Orang Asli, to durian plantations.[97]

The prevalence of the Musang King and Monthong varieties in Malaysia and Thailand, respectively, has led to concerns about a decrease in the durian's genetic diversity at the expense of higher-quality varieties.[95] A 2022 study of durian species in Kalimantan, Indonesia, found low genetic diversity, suggestive of inbreeding depression and genetic drift.[98] Additionally, these dominant hybrid varieties are more susceptible to pests and fungal diseases, requiring the use of insecticides and fungicides that can weaken the trees.[95]

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