Lens culinaris (PROSEA)

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Plant Resources of South-East Asia
Introduction
List of species


Lens culinaris Medikus

Protologue: Vorles. Churpf. Phys. Ges. 2: 361 (1787).
Family: Leguminosae
Chromosome number: 2n= 14

Synonyms

  • Lens esculenta Moench (1794).

Vernacular names

  • Lentil (En)
  • lentille (Fr)
  • Thailand: thua daeng
  • Cambodia: lânti.

Origin and geographic distribution

Lentil is one of the oldest pulse crops and of ancient cultivation in W. Asia, Egypt and S. Europe. Now it is widely cultivated in temperate and subtropical regions, and in the tropics at higher elevations. It is most important in the Indian subcontinent.

Uses

In India split seeds (dhal) are used in soups, young pods are used as a vegetable. Flour from ground seeds, mixed with flour from cereals, is considered a nourishing food. In parts of India the whole seed is often eaten salted and fried.

The whole plant, green or dry, provides excellent fodder and green manure. Seeds are a source of commercial starch for textile and printing industries. Lentils are supposed to remedy constipation and other intestinal afflictions. In India lentils are poulticed onto slow-healing sores.

Production and international trade

World area under cultivation is about 1.8 million ha with a production of about 1.1 million t seeds/year. India is the major producer with 428 000 t/year from 925 000 ha.

In the Near East, production is mainly for local consumption. Turkey is the largest exporter (production 200 000 t/year from 200 000 ha).

Properties

Dry seeds contain per 100 g edible portion: water 11 g, protein 24 g, fat 1.8 g, carbohydrates 59 g, fibre 1.8 g and ash 2.2 g. The energetic value averages 1450 kJ/100g. Seed weight varies between 1 and 9 g/100 seeds. Lentils are considered to be the most easily digested of the grain legumes.

Botany

  • An annual, much-branched herb, with square stems up to 50(-75) cm tall.
  • Leaves with 3-8 pairs of leaflets, usually ending in a tendril; leaflets narrowly obovate-elliptic, 8-18 mm × 2-5 mm.
  • Flowers small, blue to white, 1-4 together in axillary racemes.
  • Pods rhomboidal, laterally compressed, ca. 6-20 mm × 4-12 mm, 1-2-seeded.
  • Seeds lens-shaped, ca. 3-9 mm in diameter, green, brownish green or light red speckled with black.

Seedling with hypogeal germination. For germination a minimum temperature of 15°C is required, optimum temperature is 18-21°C.

Flowering starts 6-7 weeks after sowing. Harvest is possible 3-4 months after sowing. Lentils are usually self-fertilized, but cross-pollination up to 0.8% occurs. Lentils are nodulated byRhizobium leguminosarum.

At present, L. culinaris is divided into 3 subspecies:

  • subsp. culinaris: stipules entire, lanceolate; leaflets 6-16; peduncles aristate, shorter or subequal to the rachis; calyx teeth smaller, subequal or greater than corolla.
  • subsp. nigricans (M. Bieb.) Thell.: stipules toothed; leaflets up to 10; peduncles aristate, longer or subequal to the rachis; calyx teeth subequal or greater than corolla.
  • subsp. orientalis (Boiss.) Ponert: stipules entire; leaflets 6-12; peduncles non-aristate, usually awned, longer or subequal to the rachis; calyx teeth smaller or subequal than corolla.

Most cultivars belong to subsp. culinaris.

Ecology

Optimum mean temperature for good yield is around 24°C. Annual mean temperatures of 6-27°>C are tolerated. Average moisture requirement is 750 mm/year, annual precipitations of 280-2430 mm are tolerated. Frost and temperatures above 27°C affect growth seriously.

Lentils tolerate a pH of 4.5-8.2, optimum pH is 5.5-7.

In the tropics, lentils are cultivated up to 3800 m altitude, but the crop is not suited to the hot humid tropics. They are less damaged by drought than by waterlogging. They thrive on a wide range of soils from light loams and alluvial soils to black cotton soils, but best on clay soils.

Lentils are quantitative long-day plants, some cvs tending to be day-neutral.

Agronomy

Lentil is propagated by seed. The field should be plowed and harrowed to a fine texture. Seeds may be either broadcast or sown in drills at a rate of 25-90 kg/ha, in rows at 60-90 cm distance and plants 17-30 cm apart, if sole cropped.

Lentil, however, is seldom sole cropped. In India it is grown intercropped with e.g. rice, barley, castor and mustard, with seed rates of 11-13 kg/ha. In other areas it is often rotated with wheat or grown as a winter crop.

Weed control is important. Two weedings are usually sufficient for weed control during establishment, or pre-emergence herbicides are applied. In the Middle and Near East broomrapes (Orobanche spp.) parasitize the crop.

The crop is usually rainfed. Fertilizer application is not a common practice, but some gift at planting and at flowering stage may be beneficial.

Harvesting takes place when the pods are golden-yellow and the lower ones are still firm (to prevent shattering). At harvest plants are cut to ground level, dried for 7-10 days and then combined or threshed. Seed yields range from 340-675 kg/ha in dry cultivations, may increase to 1700 kg/ha with irrigation and have reached 3000 kg/ha in experiments. Lentil seed requires careful cleaning as it is often badly contaminated with weed seed. Seeds should be dried to a moisture content of 11-14%. Below 11% hard shell and breakage problems arise.

Major diseases are the wilt Fusarium oxysporum f. sp. lentis, the blight Ascochyta lentis and the rust Uromyces fabae. Major pests are caused by pea leaf weevils (Sitonia spp.) and the gram caterpillar (Heliothis obsoleta).

Genetic resources and breeding

ICARDA, Aleppo, Syria, the world centre for lentil crop improvement, has 6000 lentil accessions from 47 different countries.

Breeding objectives are: adaptation to mechanized harvest (erect types, resistance to lodging and to fruit dehiscence), reducing hazards from pests, diseases and weeds, increasing yield and stability of yield, adaptation to short growing season with limited moisture resources.

Wild relatives are urgently needed to improve the tolerance to environmental stresses. Wild relatives are:

  • L. culinaris subsp. orientalis (formerly Lens orientalis (Boiss.) Handel-Mazzetti), occurring in the Near East, possibly the progenitor of the cultivated lentil;
  • L. culinaris subsp. nigricans (formerly Lens nigricans (M. Bieb.) Godron);
  • L. ervoides (Brign.) Grande, tropical Africa and Mediterranean region;
  • L. montbrettii Fisch. & Mey. (now transferred to the genus Vicia, 2n= 12).

Prospects

The prospects are good for this most nutritious pulse. Especially in N. and S. America production is increasing because farmers wish to include legumes in rotations with cereals.

Being a crop for marginal areas, there is an urgent need for well-adapted, short duration cultivars. In S.-E. Asia it might be an interesting crop for dry, poor, high-altitude areas.

Literature

  • Muehlbauer, F.J., Cubero, J.I. & Summerfield, R.J. Lentil. In: Summerfield, R.J. & Roberts, E.H. (Editors), 1985. Grain Legume Crops. Collins, London. p. 266-311.
  • Webb, C. & Hawtin, G.C. (Editors), 1981. Lentils. Farnham Royal Commonwealth Agricultural Bureau.

Authors

  • P.C.M. Jansen