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Ram, R., D. Catlin, J. Romero, and C. Cowley. 1990. Sesame: New approaches for crop improvement. p. 225-228. In: J. Janick and J.E. Simon (eds.), Advances in new crops. Timber Press, Portland, OR.

Sesame: New Approaches for Crop Improvement*

Raghav Ram, David Catlin, Juan Romero, and Craig Cowley

  6. Table 1
  7. Fig. 1


Sesame (Sesamum indicum L.), thought to have originated in Africa, is considered to be the oldest oilseed crop known to man and is now grown in many parts of the world including the U.S. Sesame seed is an important source of edible oil and is also widely used as a spice. The seed contains 50-60% oil which has excellent stability due to the presence of natural antioxidants such as sesamolin, sesamin and sesamol (Brar and Ahuja 1979). The fatty acid composition of sesame oil varies considerably among the different cultivars worldwide (Yermanos et al. 1972, Brar 1982). After oil extraction, the remaining meal contains 35-50% protein, and is rich in tryptophan and methionine. Seeds with hulls are rich in calcium (1.3%) and provide a valuable source of minerals (Johnson et al. 1979). The addition of sesame to the high lysine meal of soybean produces a well balanced animal feed.

Total world production of sesame in 1986 was 2.4 million metric tons, 65% of which was produced in Asia (FAO Production Yearbook 1987). The U.S. is the largest importer of sesame, importing about 40,000 metric tons per year mostly from Mexico. Almost all sesame consumed in the U.S. is as a spice for food products such as hamburger buns and other bakery goods. Minor uses of sesame oil include pharmaceutical and skin care products and as a synergist for insecticides (Salunkhe and Desai 1986).

Although a major world oilseed crop, sesame is primarily grown by small farmers in developing countries in the southern latitudes. Crop development programs in these countries are either small or nonexistent, and little progress has been made during the past 20 years. A revitalization of sesame research using modern plant breeding knowledge and new technologies could be of great value in improving the crop.


Sesame yields are highly variable depending upon the growing environment, cultural practices, and cultivar. Worldwide yields averaged about 340 kg/ha in 1986; however, yields as high as 2,250 kg/ha have been obtained in test plots in Texas (Brigham 1985). A major contributing factor to low yields in sesame is that the seed capsules shatter causing a loss of large amounts of seed, particularly when the crop is machine harvested. Sesaco Corporation in Yuma, Arizona, has developed semi-indehiscent commercial cultivar with yields ranging from 600-1600 kg/ha (Brigham 1987).

A panel of sesame experts recently met in Vienna under the auspices of the FAO and summarized plant breeding objectives for sesame improvement (Ashri 1987). These included improved seed retention in the capsule, increased oil content, uniform maturity and disease resistance.

A considerable amount of mutation and plant breeding work has been undertaken in several laboratories throughout the world. Mutation breeding has been successful in producing generic lines with the determinate habit. Combining the high-yield trait with the semi-indehiscence trait could prove advantageous for developing a machine-harvested sesame crop.

An early maturing line with 3 seed capsules per axil was selected from a composite population in California (Paul Brookhouzen, personal communication). Preliminary tests at a field nursery in Minnesota showed encouraging yields, thus demonstrating a potential for selection of lines suitable for a short growing season.


Several opportunities now exist for sesame improvement as a result of recent developments in plant tissue culture and generic manipulation of crop plants. Sesame plants can be regenerated from shoot apical meristems and hypocotyl segments and grown to maturity in less than four months (Fig. 1A). Similar reports of successful plant regeneration from hypocotyl segments have recently been published (George et al. 1987). This provides an opportunity for generic transformation using Agrobacterium as the vector.

Shoots regenerated via organogenesis from apical meristems and hypocotyl segments involves little or no callus issue production and variability in the progeny of regenerated plants is expected to be minimal. Thirty-nine seeds from 12 regenerated plants were planted in the greenhouse. Seeds from these second generation plants were analyzed and showed no major variation in fatty acid composition (Table 1).

Tissue culture methods involving a callus phase or regeneration via somatic embryogenesis are known to produce stable variants (Armstrong and Phillips 1988). We have successfully induced somatic embryos directly from the surface of the zygotic embryos of sesame in culture. Somatic embryo induction in six cultivars ('Aceitera', `Arawaca', `Turen', `Piritu', `Maporal' and `Inamar) varied from 50 to 100%. A large number of plants can be regenerated using such a system (Fig. 1B). To date, over 500 plants of five sesame genotypes have been regenerated. Their progeny will be screened for variation in characteristics such as seedling growth, vigor, placental thickness, capsule dehiscence, seed size, seed dormancy, yield, oil content and oil quality.

Callus cultures derived from cotyledons and hypocotyl segments were induced to produce embryos, although induction frequencies were low. Long-term callus culture systems would be useful for in vitro selection studies involving selective agents such as pathogenic fungal toxins, herbicides, and minerals.

To further enhance variability induced in tissue culture, embryogenic sesame cultures were also subjected to in vitro mutagenesis during culture induction. Several plants regenerated from these cultures showed morphological variations such as stem fasciation and differences in vigor and branching. Progeny seed will undergo further field evaluation and biochemical analysis.

Tissue culture methods can also be used to facilitate wide crosses using embryo culture techniques. Although conventional hybrid crosses between cultivated sesame and its wild relatives have been attempted (Nayar and Mehra 1970), in most cases hybrids were difficult to produce. In preliminary studies, we cultured zygotic embryos at various developmental stages, and plants were regenerated from embryos obtained 15 days after pollination. Similar methods, could be used to regenerate plants from embryos generated from wide hybrid crosses.


The technologies currently being developed at Sungene for sesame and other oilseed crops, such as sunflower, rapeseed and cotton, offer great potential for sesame improvement. An integrated approach combining cell biology, molecular biology, biochemistry and plant breeding needs to be undertaken using all available technological advancements.

Variants in biosynthetic pathways resulting in altered fatty acid profiles of triglycerides in oil have been produced via tissue culture in sunflower and rapeseed (Ram et al. 1988). Similar fatty acid changes can be expected in sesame through somaclonal variation or direct gene introduction for specific biochemical modifications. Increased amounts of oleic acid, long-chain fatty acids and antioxidants should enhance the attractiveness of sesame for specialty chemical markets.


*Acknowledgments. The authors wish to thank Ms. Alexi Miller for critical review of the manuscript, Ms. Tammy Branch for graphics preparation and Ms. Leona Tarrice for word processing.
Table 1. Fatty acid composition of oil in R, seeds (second selfed generation from tissue-cultured regenerants) of sesame.

Fatty acidControlR2ControlR2

Fig. 1. Sesame plant regeneration in tissue culture. A. Shoot proliferation from hypocotyl segments. B. Plants regenerated from zygotic immature embryos.

Last update August 27, 1997 by aw