Lycopersicon

(tomato), a genus of annual or perennial (in the tropics) herbs and subshrubs of the family Solanaceae; the plants are sometimes assigned to the genus Solanum (nightshade). The tomato is native to South America. Wild species have been found in Peru, Ecuador, and Chile. The tomato is widely cultivated throughout the world. It appeared in Europe—in Spain, Portugal, and Italy—in the mid-16th century. The plant first became known in Russia in 1780.

The genus Lycopersicon is usually divided into three species: L. peruvianum, L. hirsutum, and L. esculentum. The last has three subspecies: ssp. spontaneum (wild tomato), ssp. cultum (cultivated tomato), and ssp. subspontaneum (semicultivated tomato). There are about 2,000 varieties and forms of L. esculentum. It is an annual. Its decumbent or erect stems are naked or slightly pubescent. The leaves are odd-pinnatisect. The inflorescence is a simple, compound, or complex bostryx. The flowers vary in size, and their coloration is any one of various shades of yellow. The ovary is spherical, elongate, smooth, ribbed, and two- or many-celled. The style is cylindrical and sometimes fasciated.

Lycopersicon is a facultative self-pollinator. The fruit, a juicy two- or many-celled berry, may be rounded, flat-rounded, ellipsoid, elongate-oval, plum-shaped, or pear-shaped. It ranges in color from dark red and orange to pale pink, light yellow, and white. The fruit measures 3–10 cm across and weighs 20–900 g or greater.

The fruits contain 4.5–8.1 percent dry matter (50 percent of which is soluble sugars), 3.5–8.5 percent organic acids, 0.87–1.7 percent cellulose, and 0.13–0.23 percent pectins. One hundred grams of the fruits contain 4 mg sodium, 268 mg potassium, 11 mg calcium, 12 mg magnesium, 0.6 mg iron, 0.097 mg copper, 27 mg phosphorus, 14 mg sulfur, 40 mg chlorine, and 0.189 mg manganese. One kilogram contains 0.3–1.6 mg vitamin B_1; 0.5–6.0 mg vitamin B₂, 4.3–5.0 mg vitamin PP, and 200–450 mg vitamin C. Carotene is also present. The fruits mature 80 to 140 days after the appearance of shoots. The tiny, flat seeds are ovate or triangularly kidney-shaped. They are pointed at the base, and their coloration is light or dark yellow, with a grayish tinge.

The tomato is a cold-sensitive crop that cannot survive temperatures below freezing. The optimum temperature for the sprouting of seeds is 20°–25°C. The optimum temperature for three or four days after the appearance of shoots is 10°–12°C during the day and 8°–10°C during the night. The plants usually do not blossom at temperatures below 15°C. The optimum temperature for growth and development is 20°–25°C. Tomato plants are relatively drought resistant. They grow best with a soil moisture content of 60–70 percent and an air humidity of 45–60 percent. Tomatoes can be grown in any soil with a pH of no less than 4.5, but they prefer loose, warm, fertile soils.

The fruits may be eaten fresh. The canning industry uses tomatoes for salting and pickling and in the production of tomato puree, juice, paste, and sauce.

In 1974 tomatoes occupied more than 225,000 hectares (ha) in the USSR. The gross annual harvest is more than 3.5 million tons, constituting 15 percent of all vegetable production. More than 50 percent of the crop is processed. In 1974 tomatoes occupied 197,000 ha in the USA (yielding about 370 quintals/ha), 113,000 ha in Italy (yielding more than 270 quintals/ha), 26,000 ha in Bulgaria (yielding 300 quintals/ha), and 17,000 ha in Hungary (yielding more than 210 quintals/ha).

About 100 tomato varieties are grown in the USSR. The best varieties for cultivation in the open ground are Alpat’eva 905a, Volgogradskii 5/95, Gruntovyi gribovskii 1180, Novinka Pridnes-trov’ia, and Talalikhin 186. Most suitable for cultivation in sheltered ground are Leningradskii skorospelyi, Ukrainskii teplich-nyi, Teplichnyi Nikulina, and Ural’skii mnogoplodnyi.

Tomatoes are raised in the open ground from seeds or seedlings. Seedlings are grown in hothouses, in hotbeds, in warmed beds, and under plastic-film coverings. Various methods are employed. The seedlings may or may not be thinned. Sometimes seeds are sown in a hotbed, and the sprouts are subsequently thinned. Plants are frequently grown from seeds or transplants in peat-compost pots or blocks; the transplants are set out after 45 to 65 days in square or square-cluster formations on a level surface, in beds, or in ridges. Depending on the variety, the region, and the method of planting, 25,000 to 50,000 plants are set out per ha.

In southern regions of the USSR tomato seeds are sown with vegetable or grain-vegetable seeders in square-cluster or broad-row formation. The sowing rate is 2.5–3 kg/ha for row planting and 1–1.5 kg/ha for cluster planting.

Care of the plants involves systematic loosening of the soil, weeding, hilling, feeding, formation of a bush (in northern regions), irrigation, and control of pests and diseases. The most common diseases of tomato plants are macrosporiosis, Septoria leaf spot, Phytophthora rot, wilt, blossom-end rot of tomato, big bud, and mosaic of tomatoes. The most common pests are wire-worms, mole crickets, cutworms, the gall nematode, the melon aphid, and the whitefly (in hothouses).

REFERENCES

Kul’turnaia flora SSSR. Moscow-Leningrad, 1958.
Biokhimiia ovoshchnykh kul’tur. Leningrad-Moscow, 1961.
Brezhnev, D. D. Tomaty, 2nd ed. Leningrad, 1964.
Zhuchenko, A. A. Genetika tomatov. Kishinev, 1973.

D. D. BREZHNEV

Lycopersicon

Lycopersicon

Lycopersicon

REFERENCES

Lycopersicon

Synonyms for Lycopersicon

noun tomatoes

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