Sesamum orientale (PROSEA)

Plant Resources of South-East Asia Introduction

List of species

Sesamum orientale L.

Protologue: Sp. pl.: 634 (1753).

Family: Pedaliaceae

Chromosome number: 2n= 26

Synonyms

• Sesamum indicum L. (1753),
• S. luteum Retz. (1791),
• S. oleiferum Moench (1802).

Vernacular names

• Sesame, gingelly, benniseed (En)
• Sésame (Fr)
• Indonesia: bidjan, lenga (general), wijen (Javanese)
• Malaysia: bijan, lenga
• Philippines: sesame, linga (Pilipino), langa (Ibanag), lunga, langa (Bisaya), lugna (Bikolano), linga (Ilokano), ahon-holi (Tagalog)
• Cambodia: longo
• Laos: nga
• Thailand: nga
• Vietnam: cây vừng, mè.

Origin and geographic distribution

Sesame is probably the most ancient oilseed used by man, its domestication lost in the mists of antiquity. It is considered to have originated in Africa, most probably in Ethiopia, although there is also evidence supporting an Indian origin. As early as 2100-2000 BC sesame was an important crop in Mesopotamia, which became the main centre of distribution of sesame as a domesticated plant. King Sargon II (722-705 BC) considered the oil so important that he introduced price control measures which remained in place during the first millennium BC. Sesame found in excavations at Harappa (Pakistan) was dated at 2000 BC. The "Medical Papyrus" of Thebes (Egypt), of about 1500 BC, lists herbal remedies that include sesame oil and seed. The Greeks and Romans spread sesame throughout the Mediterranean, but it was reported from Britain only in 1731. In the 6th Century BC, it achieved such prominence in China that it was used as currency. In Japan it was an established field crop by 1700 AD and now produces the most highly regarded edible oil. In Marco Polo's travels he noted excellent sesame oil in Afghanistan and a plentiful supply in Sri Lanka. India may have received sesame from Malaysia and Indonesia before 1500 BC, while it was mentioned in the Athavaveda of about 1000 BC as tila. It is now a major oilseed and the preferred edible oil. The earliest records from subSaharan Africa are those of early explorers; this region later became a major seed exporter. The Portuguese introduced sesame to South America, and slaves are credited as having introduced sesame to North America at the end of the 17th Century. Sesame is widely planted in Burma (Myanmar) and also cultivated elsewhere in South-East Asia, particularly in Thailand and Indonesia.

Uses

Sesame seed, flour and oil are utilized in a very wide range of mostly edible products. Pure and crude sesame oil pressed from the seed can be used directly as a cooking oil while the refined oil is utilized as a salad oil or wherever an edible oil of high keeping quality is needed. In India sesame oil has to make up 5% of vegetable ghee, to facilitate detection of adulteration of ghee made from butter. The oil is also an important constituent in the production of pharmaceutical products, cosmetics, soap, and as a perfume fixative. In India, the oil is used for anointing and conditioning the skin. Whole seed may be eaten raw, roasted and dried. It is ground into a tasty paste known as "tahini". It is a major ingredient in various sweets and a garnish of breads and pastries. The minor components sesamin and sesamolin are effective synergists of pyrethrin, a natural insecticide. The presscake is a valuable stock feed. It is usually too expensive for general use but is utilized by growers for their domestic stock. In times of famine, the cake also provides a nutritious emergency food.

Production and international trade

World production of sesame seed has grown only very gradually since the 1970s, despite an increasing demand for sesame oil in nonEuropean countries, and amounted to 2.7 million t in 2000. International trade in sesame seed declined in favour of other more cheaply produced oilseeds. Africa, with an estimated 20% of total world production up to 1980, formerly contributed nearly 70% of world exports, with Sudan dominating and frequently accounting for half of the world exports; from 1970-2000 production in Sudan fluctuated around 200 000 t. In Burma (Myanmar) and China however, the area planted increased to supply local and regional demand, growing to 300 000 and 700 000 t, respectively. Annual production in India remained stable at about 500 000 t. Practically all world trade in sesame is as seed, and only minor quantities of oil and cake are shipped. Some 100 000-200 000 t of sesame seed is available annually for export; most movement is between neighbouring South-East Asian and African countries. Japan, Italy and China are major markets for international trade, with Israel, Saudi Arabia and Greece being substantial consumers.

Properties

Sesame seed contains per 100 g edible portion: water 5 g, protein 20-25 g, fat 45-50 g, carbohydrates 16 g and fibres 5 g; it also contains vitamin A, thiamine, riboflavin, niacin and traces of ascorbic acid. The seed is rich in phytic and oxalic acid which on chelation with calcium create a slightly bitter taste. Crude sesame oil varies from dark to pale yellow while the refined oil is clear, pale yellow and has a nutty flavour. It consists of glycerides with as major fatty acids oleic acid (36-54%) and linoleic acid (38-49%). Other components are the saturated fatty acids: myristic acid (0.1% or less), palmitic acid (8-12%), stearic acid (3.5-7%) and arachidic acid (0.5-1%). The oil contains 1.2% unsaponifiable matter that includes tocopherols, and lignans including sesamin (0.1-0.6%), sesamolin (0.25-0.3%) and sesamol which give the oil its remarkable resistance to oxidation. Extracted sesame cake varies in colour from light yellow to greyish black depending on the dominant seed coat colour. Its chemical composition is also variable depending on seed type, method of oil extraction and whether it is hulled or unhulled. The protein content of Indian sesame cake ranges from 35% (expeller-pressed, unhulled) to 47% (hexane-extracted, hulled). It is high in calcium and phosphate but low in lysine, which must be supplemented by high lysine feeds. Crude fibre content in cake from unhulled seed is 5-6%, but only about 3% in cake from hulled seed.

Description

• Erect, stout, branched, aromatic, annual herb, 0.5-2 m tall. Root system welldeveloped with taproot strongly tapering, up to 90 cm long, bearing many laterals.
• Stem firm, square with ribs at each corner, less distinct when young, up to 1 cm in diameter at base, bright pale green, sparsely pilose, glabrescent or glabrous but characteristic hyaline glands present on all parts, except the oldest, glands composed of 4 globular cells and a basal one, becoming white with drying.
• Leaves very variable within and between plants, petiolate, lower ones decussate, higher ones subopposite, highest ones spirally arranged in 4 rows, all leaves densely pilose beneath on the veins and near margin, with a few globules, between veins sparsely pilose with many globules, sparsely pilose above; petiole hemicylindric, canaliculate, at least at base, up to 17 cm long, higher leaves gradually shorter petioled; lowest leaf blades entire to 2-3-lobed, in outline ovate to broadly ovate, 10-21 cm × 5-13 cm, margin usually entire or partly crenate to serrate; higher ones lobed to trifoliolate, lobes or leaflets narrowly elliptical, 9-17 cm × 3-7 cm, margin entire, crenate or serrate; highest ones bracteolar, narrowly elliptical, 5-15 cm × 1-3 cm, margin entire.
• Flowers single or 2 or more in the axil of upper leaves, early flowers larger than later ones; pedicel 2-5 mm long, pilose with globules, brownish to bluish dark green, with two small deciduous lateral bracteoles and in axil of each bracteole a yellowish, cup-shaped to disk-shaped, apically 5-lobed gland is present; calyx slender, 5-lobed, lobes oblong, 4-7 mm × 1-1.5 mm, base slightly connate, apex acute, pilose; corolla campanulate, 2-3.5 cm × 1.5-2.5 cm, horizontally flattened, base slightly bent and widened, rim undulate 5-lobed, variable in colour and markings (white in pale-seeded forms, violet in brown-black-seeded forms, often yellow-spotted), lobes about 1 mm long, lowest lobe widely ovate, revolute, apex acute to retuse; stamens 4, the upper 2 shorter than lower 2, implanted at base of corolla, filaments 8-9 mm or 12-13 mm long, white to slightly purplish, between the upper stamens, a staminode of variable length is present; ovary superior, about rectangular longitudinally, rounded to quadrangular in cross-section, 5 mm × 2 mm, with greyish, velutinous to woolly hairs, bicarpellate, 4-locular by intrusive growth of parietal placentae; style 1 cm long, ending in 2-lobed stigma 3 mm long.
• Fruit a 4-locular, many-seeded capsule, 1.5-3 cm × 0.5-1 cm, 2.5-3 times as long as broad, rectangular in cross-section, with 4 deep grooves and a short triangular beak, grey-brown at maturity.
• Seed flattened ovoid, 2-3 mm in diameter, 0.5-1 mm thick, on one side mostly narrowly margined all round and with a longitudinal midrib, the opposite surface margined only at the base and without a midrib, surfaces moderately rough, yellow-white, greyish, brown or blackish, often with vein-like darker discolourations.

Growth and development

In sesame seed germination is moderately slow and seedlings grow slowly until they reach a height of 10 cm; thereafter, growth is rapid. Branches develop when the plant is 25 cm tall. The degree of branching is cultivar specific and non-branching cultivars exist. Growth habit is generally indeterminate, but determinate cultivars have been selected. Flowers arise in leaf axils on the upper stem and branches, and the node number on the main shoot at which the first flower is produced is a cultivar characteristic and highly heritable. Most flowers open at 05.00-07.00 h., wilt after midday, and are shed at 16.00-18.00 h. Anthers release pollen shortly after the flowers open; the interval is a cultivar characteristic. The stigma is receptive one day before flower opening and remains receptive for a another day. Under natural conditions, pollen remains viable for about 24 hours. Flowers are mostly selfpollinated, but insect pollination is common. Up to 10% crosspollination occurs, but this may reach 50% in specific cultivars. Sesame can be harvested 80-150 days after sowing. Capsules near the stem base normally ripen first, while those nearest the tip ripen last. The number of capsules per plant is directly related to the number of flowers, but climate can affect the percentage of fertilized flowers. Active dry matter accumulation and synthesis of oil occurs between 12-24 days afer fruit set, but continues at a reduced rate up to 27 days, with a slight fall in oil content before maturity. The free fatty acid percentage is highest at the beginning of synthesis, declines rapidly around 18-22 days and then more gradually until seed maturity. In most cultivars, dry mature fruits split open and seeds are shattered.

Other botanical information

At present the genus Sesamum L. comprises about 36 species but an overall revision of the genus will probably reduce this number. Many species occur in Africa (18 exclusively), 8 in the IndiaSri Lanka region (5 exclusively) and 4 in South-East Asia. Within Sesamum the basic chromosome numbers are x = 8 and x = 13 and 2 n = 26, 32, or 64. Among the species with 2 n = 26 are S. capense Burm.f., S. malabaricum Burm., S. mulayanum Nair and S. orientale . S. radiatum Thonn. ex Hornem., which is sometimes cultivated for its oil-rich seed (also in South-East Asia), has 2 n = 64. From hybridization experiments it is clear that many species can be crossed successfully and many so-called species may turn out to be identical.

The scientific name of sesame remains contended, S. orientale or S. indicum , two names of Linnaeus published at the same time in Species Plantarum of 1753, for what later was correctly considered as being one species. In such cases either of the 2 names can be chosen as the correct name, but as soon as a choice is made, others have to respect that choice. Roxburgh was the first, and he chose S. orientale in 1832, which choice is followed here.

Within S. orientale no cultivar groups have been formally recognized, but existing cultivars are numerous. Characters which may typify cultivars include branching habit (branched or unbranched), growth habit (indeterminate or determinate), fruit dehiscence (dehiscent, partially dehiscent or indehiscent), and seed colour (white, grey, yellow-white, brown, black). Existing botanical classifications of cultivated sesame into subspecies and varieties need revision and reclassification into cultivars and cv. groups.

Ecology

Sesame is basically a crop of the tropics and subtropics, but newer cultivars have extended its range into more temperate regions. It occurs mainly between 25°S and 25°N, but up to 40°N in China, Russia and the United States, 30°S in Australia and 35°S in South America, generally below 1250 m altitude. Sesame is a short-day plant, but many cultivars have become adapted to various photoperiods. With 10-hour days it will normally flower in 42-45 days after sowing. Temperature and moisture have major modifying effects on the number of days to flowering. A short photoperiod can increase the number of capsules per plant in early and mediumlate cultivars. High temperatures are required for optimal growth and production. Temperatures around 30°C encourage germination, initial growth and flower formation, but up to 40°C will be tolerated by specific cultivars. Temperatures below 20°C normally delay germination and seedling growth, and below 10°C inhibit both. Approximately 150 frostfree days are required and a hard frost at maturation reduces seed and oil quality, adversely affects the minor seedoil constituents sesamolin and sesamin and kills plants. However, in Hubei (China) seed oil content was found to be higher in genotypes from the colder north than in those from the warmer south. It is also higher in genotypes with light-coloured seeds. Sesame is considered drought-resistant. Established plants can withstand high moisture stress, but seedlings are extremely susceptible. It will produce an excellent crop with a rainfall of 500-650 mm. Ideally, 35% of rain should fall during germination until first bud formation, 45% until main flowering and 20% at seed filling. Rain should cease as first pods begin to ripen. Heavy rain at flowering drastically reduces yield. Seedlings are susceptible to waterlogging. After stem elongation it is also susceptible to wind damage. Sesame thrives on moderately fertile and welldrained soils, but is sensitive to salinity. Soils with a neutral to slightly alkaline reaction are preferred and sesame does not thrive in acid soils.

Propagation and planting

Land preparation for small grains such as wheat and sorghum is also suitable for sesame. Level land is important to ensure an even depth of planting but land may be ridged for better drainage in areas where high-intensity storms are common. Immediately before planting, the land should be harrowed to kill weeds since sesame seedlings have slow initial growth. Weed control while plants are small is difficult and the seedbed should be as weedfree as possible. Many types of sowing equipment are suitable. Depth of planting is usually 2-5 cm, but can be 10 cm in loose soil. Soil should not be compacted after sowing. Even depth of planting is important and ensures even crop emergence and growth which facilitates subsequent tillage operations and harvesting. Plant density depends on the prevailing environment, seed rates of 2-10 kg per ha are used in sole cropping. Plant populations directly influence the number of capsules per plant, and a high population or close inrow spacing tends to reduce both the number of capsules and number of seeds per capsule. Maximum yields have been obtained from crops planted 90 cm × 90 cm, while row spacings of 50-100 cm are recommended.

Husbandry

In sesame early weed control is important. Two or three shallow weedings are usually adequate. Weeding implements should be set as shallow as possible to avoid damage to the roots. Growth is rapid once plants are 10 cm tall and few weedings are needed thereafter. Close row spacing can reduce late weed growth which may be troublesome at harvest. A wide range of preemergence herbicides has been successfully used, but none of them is safe postemergence. Sesame is frequently intercropped in smallholders’ fields. Strip cropping with maize and sorghum is common which gives it protection from strong winds. Sesame has also been planted with beans and cotton. Few data on fertilizer requirements of sesame are available. The amount of nutrients removed by a crop per t seed is estimated at 30 kg N, 14 kg P and 5.5 kg K. In Korea an application of 7 kg N, 1 kg P, and 6 kg K per ha has produced a seed yield of 1755 kg/ha. Where sesame is grown on a large scale, NPK mixtures of 5-10-5, 12-12-6, and 10-14-10 at a rate of 500-700 kg per ha are commonly applied at planting. Irrigated sesame requires the equivalent of 900-1000 mm rain for optimum yields. If more than 1000-1200 mm are required, sesame is usually replaced by other oilseeds better able to utilize large volumes of water. In Asia sesame is often grown as a second crop after rice, and is then sown in the rice stubble. In addition to residual soil moisture only a single irrigation is required.

Diseases and pests

Many of the damaging fungal diseases that attack sesame are of restricted distribution. Some of the most important ones are known to be seed-borne so disinfection of seed should be routine, unless seed from disease-free areas is available. The most damaging diseases are bacterial leaf spot caused by Pseudomonas sesami and leaf spot caused by Alternaria sesami , and Cercospora . P. sesami causes light-brown, dryish, angular spots with a darker, more purple margin; spots coalesce to form large, necrotic areas on the leaves. Alternaria sesami is a seed-borne pathogen that infects stems, leaves and green capsules. Dark brown, water-soaked lesions mainly on the stem are major symptoms, although lesions may occur also in midribs and leaf veins without the spots. Cercospora leaf spots are irregular brown spots of 2.5-10 mm. Stem anthracnose is important in Asia and Africa. Infected stems become discoloured and dull green and turn brown or black later. Its cortical tissues crack, exposing the inner tissues and brown streaks or large spots may be seen along the stem, either along the whole stem or alternating with healthy tissues. Fusarium wilt can also be devastating to susceptible cultivars. The most damaging viral or mycoplasmal disease is phyllody, especially in India and Burma (Myanmar). The characteristic symptoms are deformed flowers that remain green and with the calyx and corolla sometimes stiff and forming a half-open hood. Chemical control of these diseases is difficult and sometimes not economical. Seed treatment, planting resistant cultivars, destruction of crop residues and alternate hosts and crop rotations that give a quarantine period should all be applied.

Sesame is attacked by many insects. In some regions, those attacking flower heads and young fruits assume greatest economic importance; in others, the foliage eaters cause major losses. The reduction caused by insects can reasonably be assumed to be 25% of potential yield worldwide. Estimated damage on smallholdings and commercial crops in Africa, Asia and Central America where no or minimum pesticides are used, is usually more than onethird of the yield. Cutworms, especially Agrotis ipsilon and A. segretum are widespread and common pests of sesame. Holotrichia helleri and Valanga nigricornis are common in Indonesia. Herbivorous insects Antigastra catalaunalis and Acherontia styx occur widely but Diacrisia obliqua and Amsacta moorei are important in Asia. The bug Cyrtopeltis tenuis is present in Asia (Indonesia and other growing areas). Chemical control of sesame pests is generally unprofitable, but the extent of potential yield loss must be realized and offset as far as possible by cultural techniques. High seed rates compensate for seedbed losses and branching cultivars produce more flowers. Timing of planting to avoid the main outbreak of a major insect pest, the destruction of crop residues, and the use of resistant cultivars reduce successive infestations.

Harvesting

Sesame is harvested 80-150 days after sowing but most commonly in 100-110 days, some very shortseason cultivars in 70-75 days. At maturity, leaves and stems change from green to a yellowish, finely reddish tint. Capsules ripen irregularly from the lowest to the highest, and plants must be harvested before all capsules are mature, since field losses from shattering cultivars can reach 75%, but even non-shattering types may lose about 25%. Smallholder crops are usually harvested by hand and allowed to dry in stooks. Nonshattering cultivars can be directly combined provided this is carefully done by specially modified machines, or cut by a mower to allow the plants to dry, followed by a combine fitted with a pickup reel. Threshing equipment should be set to a low drum speed and a wide spacing between drum and concave to avoid damage to the seed.

Yield

Seed yield is directly related to the number of branches, but the total number of capsules has the greatest direct effect on seed yield. The number of seeds per capsule, their weight, oil content and other constituents vary with capsule position, irrespective of cultivar, and are also directly affected by environment. Seed yields of smallholder crops seldom exceed 300-500 kg/ha when planted in pure stands. However, under intensive, high-input production yields reach 2000-2500 kg/ha with an oil content of about 50%.

Handling after harvest

Sesame seed of less than 8% moisture content can be stored for up to 2 years in airtight containers. Bulk storage of clean and dry seed presents few problems but seed that is damaged or contaminated by extraneous material produces discoloured or rancid oil. Sesame seed is mostly processed with the seed coats although hulled seed produces higher quality oil and meal. Seed is crushed or pressed by methods ranging from the Indian "ghani" to large, modern plants. Oil extraction in Europe and Asia is done in 3 consecutive phases. The first cold pressing produces high quality oil. The residue from this process is heated and pressed to yield coloured oil that must be refined first before edible use. Further extraction of the residue gives oil that is not used for human consumption. Crude oil is filtered to remove impurities such as suspended meal and free fatty acids. The oil is also bleached and deodorized to transform it to a light-coloured and bland oil.

Genetic resources

Sesame is rich in genetic variability and much collection still needs to be done. The National Bureau of Plant Genetic Resources (New Delhi, India) now maintains about 10 000 sesame accessions, including 2500 exotic collections. Other large collections are found in the Russian Federation, the United States, Venezuela and China. These collections contain many duplicates and smaller core collections are being made of well-identified and evaluated material.

Breeding

Among the breeding objectives for sesame are higher yields, improved plant architecture, length of growing season, resistance to diseases and pests and indehiscent capsules. The degree of dehiscence is a cultivar characteristic and of great importance for mechanized harvesting. The discovery in 1943 of an indehiscent mutant produced nonshattering cultivars that were, however, difficult to thresh. The introduction of papershell capsules into indehiscent plants helped to solve this problem. Plants with partially dehiscent fruits that open slightly but generally retain their seed have also been identified. Cultivars developed by SESACO (Texas, United States) are of this type. Plant height to the first capsule is another cultivar characteristic that is important for mechanical harvesting. The discovery of genetic male sterility in sesame eased the production of hybrid seed. Induced mutations play an important role in sesame breeding. One of the most widely grown cultivars of Korea named "Ahnsankkae" has X-ray-induced disease resistance. A mutant named "dt45", with determinate growth and capsules clustered near the top, was detected in Israel. The apical capsules are often quadricarpellate and have large seeds. The modified gene has been incorporated into several newly released cultivars.

Interspecific hybridization is possible, and crosses may produce viable seeds. The Indian S. mulayanum (sometimes considered a form of S. orientale ) is similar to S. orientale and has the valuable characteristics of being resistant to phyllody and wilt. Hybrids are partially fertile. Polyploidy can be induced, but colchicin-treated plants tend to produce low yields, although the growth rate and general vigour of tetraploids can exceed those of diploids.

Prospects

Although sesame is of ancient cultivation, there is ample scope for crop improvement. The oil with its characteristic taste and excellent cooking and keeping qualities is highly appreciated in many parts of the world from the Middle East to Japan. As an annual oilseed crop well adapted to dry tropical conditions its importance in South-East Asia may increase in drier areas.

Literature

• Ashri, A., 1998. Sesame breeding. Plant Breeding Reviews 16: 179-228.
• Backer, C.A., 1951. Pedaliaceae. In: van Steenis, C.G.G.J. (Editor): Flora Malesiana. Series 1, vol. 4. Noordhoff-Kolff, Jakarta, Indonesia. pp. 216-221.
• KamalEldin, A. & Appelquist, L.A., 1994. Variation in fatty acid composition of the different acyl lipids in seed oils from four sesame species. Journal of the American Oil Chemists' Society 71(2): 135-139.
• Ram, R., Catlin, D., Romero, J. & Cowley, C., 1990. Sesame: New approaches for crop improvement. In: Janick, J. & Simon, J.E. (Editors): Advances in new crops. Timber Press, Portland, Oregon, United States. pp. 225-228.
• Salunkhe, D.K., Chavan, J.K., Adsule, R.N. & Kadam, S.S., 1992. World oilseeds: chemistry, technology and utilization. Van Nostrand Reinhold, New York, United States. 554 pp.
• Seegeler, C.J.P., 1983. Oil plants in Ethiopia, their taxonomy and agricultural significance. Pudoc, Centre for Agricultural Publishing and Documentation, Wageningen, the Netherlands. pp. 248-282.
• Weiss, E.A., 2000. Oil seed crops. 2nd Edition. Blackwell Science, Oxford, United Kingdom. 364 pp.
• Xu, B.S., Wang, W.L., Ji, Y.C., Wang, Y., Huo, X.T., 1992. A study in dry matter accumulation and the law of fertilizer requirement in sesame. Acta Agriculturae Universitatis Henanensis 26(40): 331-334.
• Yuan, T., Wang, H., Yan, W.B., Yuan, T., Wang, H., Yan, W.B., 1996. A study of the development of the flower and inflorescence in sesame. Journal Henan Agricultural Science 3: 3-6.
• Zhang, Y.X., Cheng, M., Wu, A.Z., Zhou, X.C., 1990. Cytogenetic studies in sesame (Sesamum indicum): a new taxonomic system. Acta Universitatis Pekinensis 16(1): 11-18.

Authors

E.A. Weiss and Q.D. de la Cruz