Lentil

• 1. Introduction

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  The lentil is a small, lens-shaped seed that gave its name to the optical lens. The connection runs the other way around from what most people assume. Artificial lenses and the lenses inside the animal eye were named because their archetypal shape resembles a lentil. The Latin word for the plant is lens, and that single word seeded both a kitchen staple and the vocabulary of optics. This is a plant about 40 cm tall, an annual legume whose pods usually hold just two seeds each. Yet its reach stretches from the Fertile Crescent of the Near East to a New Year's Eve table in Italy. How did a bushy herb that closes its own flowers after three days end up feeding the Indian subcontinent, anchoring Ethiopian stew, and lending Rome a family name? The answers run through caves dated to 11,000 BC, through a research station in Canada, and through the genetics of a seed coat.

• 2. A Seed That Named A Family

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  The Roman family name Lentulus may descend from lens, the Latin word for lentil. The pattern repeats across Roman naming. The name Cicero was derived from the chickpea, Cicer arietinum, and the name Fabia, carried by Quintus Fabius Maximus, came from the fava bean, Vicia faba. Legumes were close enough to Roman life to become surnames. The lentil belongs to the genus Vicia, part of the subfamily Faboideae within the family Fabaceae, the legume or bean family, in the order Fabales. The former genus Lens is now treated as a section of genus Vicia. It once held the cultivated L. culinaris alongside six related wild taxa: Lens orientalis, Lens tomentosus, Lens lamottei, Lens odemensis, Lens ervoides, and Lens nigricans. Botanists call these seven taxa rather than species, because while there is broad agreement that there are seven, there is no broad agreement that they are distinct species. Among the wild taxa, L. orientalis is considered the progenitor of the cultivated lentil. The two are most often treated as subspecies, written as L. culinaris subsp. culinaris and L. culinaris subsp. orientalis.

• 3. Anatomy Of A Pulse

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  The germinating lentil keeps its cotyledons in the ground, inside the seed coat, a habit called hypogeal growth. That choice makes it less vulnerable to frost, wind erosion, or insect attack. The plant is a diploid, bushy herb that usually stands 30 to 50 cm tall, with slender, angular stems and many hairy branches. Its rachis bears 10 to 15 leaflets in five to eight pairs, the upper leaves often turning into tendrils while the lower leaves end in a small point. One to four small flowers arise from the leaf axils, colored white, pink, purple, pale purple, or pale blue. The pods are oblong, slightly inflated, and about 1.5 cm long, normally holding two seeds about 0.5 cm across in the characteristic lens shape. Lentils are self-pollinating, and the flowers open from the lowermost buds upward in what is called acropetal flowering. About two weeks pass before every flower opens on a single branch. By the end of the second day and the third day after opening, the flowers close completely and their color fades, and the pods set three to four days later.

• 4. The Color Of The Coat

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  Seed coat color sorts lentils into the categories that move them to market. Coats fall broadly into tan, grey, green, brown, clear, or black, and the first four slowly turn brown over time. A black seed coat behaves like a pattern, masking the base color beneath, while clear coats lack pigment altogether. The color of the cotyledon inside also influences seed coat color, though it does not usually change the market classification. Patterning is usually selected against, with one famous exception. Puy or French green lentil carries marbled patterning, which comes in two genetic variants termed Marbled-1 and Marbled-2, alongside spotted, dotted, and mottled coats. A surprising rule governs all of this. Seed coat color is determined by the genotype of the seed parent, not by the genetics of the plant the seed will grow into. Inside, the common cotyledon colors are an orange-red called red, occasionally orange, and a light yellow called yellow. Three further colors have been documented: a brown-yellow, a light green, and a dark green. Red lentil varieties tend to be smaller than their green and brown counterparts, and because the seed coat is often removed, its color and pattern are not usually selected for.

• 5. Caviar And Designer Lentils

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  Beluga Black lentils took their name from beluga caviar. The cultivar behind the trade name is Indianhead, named for the Indian Head research station in Canada where it was first selected for trial. These are among the smallest cultivars, bead-like and almost spherical, with yellow cotyledon and a black seed coat. Beluga lentil began as a fodder crop and became something of a designer food in the 1990s, earning its current name for the resemblance to caviar. Its thick seed coat lets it hold its form when cooked, and it is widely used in breeding programs as a source of disease resistance. Region carries its own identities. Puy lentils, var. puyensis, are small blue-green lentils with mottling, originating from France with a Protected Designation of Origin name; grown elsewhere they are sold as French Green. Alb-Leisa are three traditional genotypes native to the Swabian Jura in Germany, protected by the producers' association Oko-Erzeugergemeinschaft Alb-Leisa. The name Spanish Brown can mislead. Modern Spanish Brown does not originate from Spain; the cultivar Pardina came from a cross made in the US and later trialled in Spain, where it became common.

• 6. From Franchthi Cave To The Field

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  The oldest known carbonized lentil remains come from Greece's Franchthi Cave, dated to 11,000 BC. The crop was domesticated in the Fertile Crescent of the Near East, then spread to Europe, North Africa, and the Indo-Gangetic plain. Unlike their wild ancestors, domesticated lentils have indehiscent pods and non-dormant seeds, meaning the pods do not split open on their own. Carbonized seeds have surfaced at sites scattered across the ancient world: Tell Ramad in Syria, dated 6250 to 5950 BC, Aceramic Beidha in Jordan, Hacilar in Turkey at 5800 to 5000 BC, Tepe Sabz in Iran, and Argissa-Magula in Greece. Lentils were part of the ancient Israelite diet, served roasted or as a soup or stew, and excavations at Tel Beit Shemesh have uncovered remains dating from the Iron Age. The plant rewards the soil that holds it. Lentils grow best in deep sandy loam with moderate fertility and a soil pH around 7, though they will not tolerate flooding or water-logged ground. They improve a soil's physical properties and raise the yield of the cereal crops that follow, an effect tied to biological nitrogen fixation. In 2023, world production of dry lentils reached 7 million tonnes, with Australia, Canada, and India together accounting for 72% of the total.

• 7. Milling, Cooking, And The Resistant Starch

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  Dal milling turns a major share of the world's red lentil into a split, polished pulse. These lentils are dehulled, split, and polished, and the moisture content before dehulling is crucial to a good result. The hull accounts for only 6 to 7 percent of the total seed weight, lower than most legumes. In the kitchen, lentils can be soaked, germinated, fried, baked, or boiled, with boiling the most common method. Cooking takes 10 to 40 minutes depending on variety, and small husked varieties like the common red lentil cook fastest and, unlike most legumes, need no soaking. Husked lentils stay whole with moderate cooking, while hull-free ones break down into a thick puree. Nutrition gives the seed a quieter distinction. Boiled lentils are 70% water, 20% carbohydrates, 9% protein, and 0.4% fat, providing 114 calories in a 100 g serving and a rich source of folate at 45% of the Daily Value, copper, and manganese. Their starch matters for people with diabetes. Only about 5 percent is readily digestible, a minimum of 10% escapes digestion as resistant starch, and more resistant starch forms as cooked lentils cool. Lentils also carry antinutrients, including trypsin inhibitors and a relatively high phytate content, though prolonged soaking, fermentation, or sprouting reduces the phytates and cooking nearly removes the trypsin inhibitor activity.

• 8. Breeding A Narrow Crop

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  The International Center for Agriculture Research in the Dry Areas, ICARDA, began its lentil breeding program in 1977. Compared with many other crops, lentil breeding and genetic research have a short history, yet the program has supplied landraces and breeding lines to countries worldwide, supplemented by efforts in India, Australia, and Canada. The crop's narrow genetic base is its central problem. Wild Lens species hold diverse traits, including disease resistances and abiotic stress tolerances, but hybridization barriers stand between many of them. Breeders sort the relatives into three gene pools by how easily they cross. The primary pool holds L. culinaris, L. orientalis, and L. tomentosus; the secondary holds L. lamottei, L. odemensis, and L. ervoides; the tertiary holds L. nigricans. Crosses generally fail between members of different pools, though plant growth regulators and embryo rescue can coax viable hybrids across the gaps. Even a successful cross can drag in undesired genes alongside the wanted ones, a problem addressed through a backcrossing program. One thread points forward from here. There is a proposed revision of the gene pools using SNP phylogeny, a step that could redraw the map breeders use to widen this ancient seed.