Agriculture knowledge

Sesame – One of the Most Ancient Oil Plants

New strains of the plant are now being created in a lab in Rehovot

This year, sesame, an ancient summer crop, was one of the hardest hit by the fickle weather. Kna’ani, one of the last local farmers who keeps planting sesame each year, planted nearly 300 dunams (75 acres) of it, of which only about 50 are left. “Like every year, we planted the sesame at the start of the fifth month, but everything got flooded. We planted a second time, but the plants didn’t sprout. It was as if something ate away at them from inside the earth.” The tender plants that did manage to grow sprouted white bell-shaped flowers, which turned into the green capsules that hold the sesame seeds.


About three months after the initial planting, the first capsules, near the bottom of the stalk, start to turn a little yellow. Even if the upper part of the stalk is also filled with flowers and capsules that have yet to ripen, it is time to pull out the plants.


The sesame capsules opens on its own as soon as it ripens, a natural reproductive mechanism, and the dozens of seeds scatter all over. If the plants are picked at the wrong time, most of the crop can be lost, and the plants must be picked by hand, lest the capsules open prematurely. Sesame plants are left to grow in the sun for two weeks. In the old days, natural rocky surfaces were the base from which they sprouted; now nylon sheets are spread on the ground. Within a short time, the capsules open, and any recalcitrant ones are helped along by being hit lightly with a stick.


The yield is very low: “At best, 50 kilos per dunam,” says Kna’ani. The local variety, which has dark seeds and is relatively low in fat, is still a sought-after item in the Palestinian Authority, and used mostly as part of theza’atar seasoning mix. Very little, however, reaches the local markets.


One of the most ancient oil plants, sesame was a major summer crop in this region for thousands of years. Ancient travelers and chroniclers cited the abundance of the crop, and the large number of oil presses where sesame oil and tahini were produced. But by the late 20th century, sesame had nearly completely vanished from fields here. Local growers − in the 1950s and ’60s, tens of thousands of dunams were planted on kibbutzim and in other communities − couldn’t compete with the low price of imported sesame. Growing the crop on a commercial scale, which requires vast amounts of land and arduous manual labor, is nowadays done exclusively in underdeveloped countries like India, China, Burma and some African countries. The sesame seeds that are used to make the “local” tahini or are sprinkled on “locally made” pastries all come from overseas and are very expensive; this exacts a heavy price from farmers who still work the sesame fields here.


An orphan plant

Dr. Zvi Peleg of the Hebrew University’s Institute of Plant Science and Genetics in Agriculture, in Rehovot, pulls an old book with yellowed pages out of the glass-doored bookcase. The carefully preserved volume is an original collection of all the botanical and agricultural research studies carried out by agronomist Aharon Aaronsohn in Palestine in 1910.


“Even then Aaronsohn figured out why sesame seeds have difficulty sprouting in a year when there is an abundance of late winter rain,” he says, pointing out the exact quote. “Rain creates a thin but hard crust in the upper layer of the earth and the delicate plants have trouble breaking through it. There is no mystery here. In traditional agriculture, centuries-old knowledge and experience pass from father to son, but mistakes also become entrenched over time and are difficult to uproot.”


Adds Peleg: “With all due respect to the preservation of seeds from year to year and from generation to generation, in the local strain of sesame you find traces of varieties that were developed in the 1960s by Israeli researchers.”


Born in 1973, Peleg is continuing the work of those researchers who were trying to create local varieties of sesame that were rich in oil and suited to mechanical harvesting. The young researcher did his doctoral work on local wheat varieties, and then took a deeper interest in sesame during a 2008 research expedition to Ethiopia to study the chick pea. “I saw laborers there harvesting sesame with a scythe and sickle, and I realized that there was tremendous research potential here,” he says.


Sesame is what researchers call an orphan plant − one that modern science hardly deals with since it is not grown commercially in Western countries. But lately, with the world having discovered the flavor and nutritional value of iron-rich sesame seeds and sesame oil, it’s getting harder for the limited number of growers and the old processing methods to keep up.


After beginning his research two years ago, Peleg’s collection now includes more than 500 different strains of sesame, from wild varieties that come from India and Africa, to strains from rural areas, the result of unique mutations that developed in accordance with varied climate and soil conditions.


In the lab, at the research farm and in a pioneering experimental commercial plot, Dr. Peleg and the students working with him are trying to create a variety of sesame that is well-adapted to the local terrain and can also be commercially grown on a large scale. The average time for developing a new strain is 12 years. It’s a long and challenging road when you are doing classic cultivation based on hybridization, but even now, a visitor can witness the techniques being used to spur nature to augment desirable qualities of various seame species (so as to increase productivity), as well as to figure out ways to deal with stubborn capsules that refuse to “open sesame.”


Haaretz, 22/8/13

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