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a genus of fruit trees of subfamily Pomaceae, family Rosaceae.
Some 60 species of Pyrus are known; more than 30 are found in the USSR. The most important species, from which the cultivated varieties originate, are the common pear (P. communis), which grows wild in Europe, western and Middle Asia; the snow pear (P. nivalis), in Europe and western Asia; the Boissier pear (P. boissieriana), in Middle Asia and Iran; the Korzhinskii pear (P. korshinskyi), in Middle Asia; the late ripening pear (P. serotina), in eastern Asia; and the Ussuri pear (P. ussuriensis), in the Far East, northeast China, and the Korean Peninsula. Trees of the cultivated varieties are distinguished by great longevity, reaching 200 years. The height is 15–20 m. The crown has a compressed pyramidal form. The root system is lightly branched and stalky, with the majority of the roots in a 20–80 cm layer of soil. The leaves are ovate and not downy; they are dark green, shiny, denate, entire, and flat or wavy at the edges. The flower buds are formed the year preceding fruit bearing and differ from the growth buds by larger dimensions and a rounded blunt tip. the blossoms are usually white (rarely, rose or red) and gathered into corymbs. The fruits are turbinate, pyriform, or elongate pyriform in shape, or at times bergamot-shaped or nearly round. They range in size from very small (to 25 g) to very large (over 300 g) and are yellow or green in color, either with or without a blush.
Pear trees are light-loving, insufficiently resistant to drought, and less hardy in frost than apple or cherry trees. For successful cultivation the summer varieties require a frost-free period of about 135 days; the fall varieties need 150–185 days, and the winter varieties, 180–200 days. Pear trees can grow in any soil (except sandy, gravelly, and saline soil) that will permit normal root development, but the best are the chernozem and chestnut soils in piedmont areas. Many varieties are not self-fertilizing, so that pollinator varieties must be provided for normal infructescence. The young stock of strong varieties starts producing fruit in the fifth or sixth year and reach full fruit-bearing capacity after 20 or 25 years. Periodicity in fruit bearing is less pronounced than in apple trees. The harvest varies, depending on the variety, the care, and the region; the average in the USSR is about 5 tons per hectare (sometimes as much as a ton from a single tree). The fruits of cultivated and wild pear trees are used in fresh, dried, and canned forms, as well as for preparing candied fruit, candied peel, and various drinks. Fruits of European varieties contain an average of 80 percent water, 10.4 percent sugars, 0.3 percent acids, 0.03 percent tannic substances, 2.6 percent cellulose, 0.4 percent nitrogenous substances, and 0.35 percent ash; vitamins B and C and provitamin A are also present. Wild pear seeds are used to grow stocks for grafting with cultivated varieties. The wood of some species is used in cabinet-making and joinery and for making musical instruments. The oleaster pear (P. elaeagrifolia) is used as a decorative plant, and the willow-leaved pear (P. salicifolia) is used to fix sandy soils.
The pear tree is the oldest cultivated plant. In the USSR it takes second place (after the apple) among seed breeds. The chief regions of cultivation are the Ukraine, Moldavia, the Northern Caucasus, Transcaucasia, Byelorussian and the Central Chernozem Zones. The northern limit runs along a line from Leningrad through Yaroslavl, Gorky, Ufa, and Orenburg. The area devoted to pear trees comes to over 6 percent of the total for fruit crops in the USSR.
Some 5,000 varieties of Pyrus are known, of which more than 280 are cultivated in the USSR. The varietal composition of pear groves is diverse and depends on natural and economic conditions. The major commercial varieties are subdivided into summer types—Bessemianka (seedless), Bon Chretien, Williams, Limonka, Clapp Favorite, Russian Malgorzhatka, and Tonkovetka (thin-branch); fall varieties— Autumn Bergamot, Ligel’s Beret, Bosc Berte, and Lesnaia Krasavitsa (forest beauty)—and winter types—Michurin’s Winter Beret, Ardenpon Beret, Curet, and St. Germain.
Cultivated varieties are produced by grafting to large and dwarf stock. Reproduction by seed is used for selecting and breeding new varieties. The best time for planting in southern regions is autumn and in middle latitudes, early spring. The planting area in fertile and well-watered soils is 8 x 6 m for large and 7 x 5 m for dwarf types; in poorer soils and in soils lacking moisture the areas should be 8 x 5 m and 6 x 4 m, respectively. For the best pollinization the pollinators and the fruit-producing trees are placed in alternating strips of 4–6 rows if both varieties are primary, or 4–6 rows of the pollinated variety with 1–2 rows of the pollinator (if it is not the primary variety in the orchard). After planting, the space between rows in the orchard is kept cleared or planted with vegetables for five to six years. In the following years, with sufficient irrigation, bare fallow is alternated with green manures and grasses. Where moisture is short, fallow and green manure alternate. In southern regions the prospects are promising for a pear cultivated through grafting onto dwarfed stock. The pests of pear trees include the pear psylla (leaf lice), pear leaf-curl aphid, pear fruit worm, pear fruit sawfly, apple curculio, winter moth, pierid butterfly, and the lackey moth. Diseases include pear scab, blights, rust, powdery mildew, and rots.
REFERENCESRubtsov, G. A. Grusha, 2nd ed. Moscow-Leningrad, 1937.
Dushutina, K. K. Kul’tura grushiν Moldavii. Kishinev, 1956.
Grusha. Moscow, 1960.
Zhukovskii, P. M. Kul’turnye rasteniia i ikh sorodichi, 2nd ed. Leningrad, 1964.
K. K. DUSHUTINA