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in zoological systemization, the aggregate of the individuals of one species that are distinguished by one or several signs (usually morphological) from the other individuals of the same species. Earlier, the term “variety” was applied to every subdivision within a species connected with mutability, starting with mutation and age-related coloring changes and going up to geographical variations. Such an indefinite understanding makes the use of the term undesirable. In accord with the International Code of Zoological Nomenclature, varieties described in 1961 or thereafter are looked upon only as infrasubspecies categories. Varieties described before 1961 are looked upon by the Codex either as subspecies or as infrasubspecies categories.
I. M. KERZHNER
in botanical nomenclature, a group of individuals or a population that differs from typical individuals of a species in secondary, weakly inherited characters (degree of hairiness, growth characteristics, color) and has no distinct area of distribution. A variety is a taxonomic category ranking lower than a subspecies and higher than a form. The appearance of varieties is due to the distribution of a species in various ecological conditions. Juniperus turkestanica has a high-altitude low-growing variety, var. fruticosa. Modern taxonomists usually avoid the designation of variety because of its indefiniteness.
in plant growing, a group of related plants developed by means of selection and possessing definite, genetically transmissible morphological, physiological, and economic characters and properties; the lowest taxonomic unit of cultivated plants.
Plant varieties are divided into local and selected varieties. The former are the product of folk selection, mainly mass selection. They are well adapted to conditions of growth, possess many economically beneficial characters, and often serve as initial material in selective breeding.
Selected varieties, which are developed by special methods at research institutions, include three distinct types, each distinguished by certain biological characteristics and by origin. One type, obtained by means of individual selection, consists of the offspring of a single self-pollinating plant, which are marked by a uniformity of all characters. The second type of selected variety consists of a homogeneous aggregate of plants, usually cross-pollinated, which may belong to different cultivated variants but have one or more common characters. The third type consists of cloned varieties, that is, selected offspring from a single plant that is propagated vegetatively, for example, by cutting, division, or grafting. Cloned varieties are the most homogeneous of the three types, often appearing in the form of chimeras.
Hybrids are developed by crossing varieties or self-pollinated lines, as well as by crossing varieties with lines. As a result of heterosis, they are distinguished by increased yield in the first generation. Closely related varieties that have similar economic and biological characters are united in groups to facilitate their study and inventory.
One of the most effective means of increasing crop yields and improving product quality is the use of the best varieties. Under production conditions, varieties deteriorate and need renovation. Old plant varieties are periodically replaced by new ones that provide larger yields and better products. In the USSR all varieties undergo state varietal testing—a special competition during which varieties best suited to production conditions are selected. The reproduction of varieties is conducted at various seed-growing enterprises. The identification of plant varieties is determined by varietal control.
REFERENCESSee references under SELECTIVE BREEDING.
IU. L. GUZHOV