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A landrace is a domesticated, regional ecotype;〔〔 a locally adapted,〔 traditional variety〔 of a domesticated species of animal or plant that has developed over time, through adaptation to its natural and cultural environment of agriculture and pastoralism, and due to isolation from other populations of the species.〔 Landraces are generally distinguished from cultivars, and from breeds in the standardized sense, although the term landrace breed is sometimes used as distinguished from the term ''standardized breed'' when referring to cattle.〔 The ''-race'' in this word refers to the taxonomic definition of ''race'' in biology, not the ethnographic sense of the word. Specimens of a landrace tend to be relatively genetically uniform, but are more diverse than members of a standardized or formal breed.〔 Some standardized animal breeds originate from attempts to make landraces more consistent through selective breeding and a landrace may become a more formal breed with the creation of a breed registry and/or publication of a breed standard. In such a case, the landrace may be thought of as a "stage" in breed development. However, in other cases, formalizing a landrace may result in the genetic resource of a landrace being lost through crossbreeding. Landraces are distinct from ancestral wild species of modern stock, and from separate species or subspecies derived from the same ancestor as modern domestic stock. Landraces are not all derived from ancient stock largely unmodified by human breeding interests. In a number of cases, most commonly dogs and horses, domestic animals have escaped in sufficient numbers in an area to breed feral populations that, through evolutionary pressure, can form new landraces in only a few centuries. In other cases, simple failure to maintain breeding regimens can do the same. For example, selectively bred cultivars can become new landraces when loosely selective reproduction is applied.〔 Increasing adoption of and reliance upon modern, purposefully selected plant strains, considered ''improved'' – "scientifically bred to be uniform and stable" – has led to a reduction in biodiversity.〔〔 The majority of the genetic diversity of domesticated species lies in landraces and other traditionally used varieties,〔 a "reservoir of genetic resources".〔 ==Characteristics== General features that characterize a landrace may include: * It is morphologically distinctive and identifiable (i.e., has particular and recognizable characteristics or properties),〔〔 yet remains "dynamic".〔 * It is genetically adapted to,〔〔 and has a reputation for being able to withstand,〔 the conditions of the local environment, including climate, disease and pests, even cultural practices.〔 * It is not the product of formal (governmental, organizational, or private) breeding programs,〔 and may lack systematic selection, development and improvement by breeders.〔〔〔 * It is maintained and fostered less deliberately than a standardized breed, with its genetic isolation principally a matter of geography acting upon whatever animals that happened to be brought by humans to a given area.〔 * It has a historical origin in a specific geographic area,〔 usually it will have its own local name(s),〔〔 and will often be classified according to intended purpose.〔 * Where yield (e.g. of a grain or fruit crop) can be measured, a landrace will show high stability of yield, even under adverse conditions, but a moderate yield , even under carefully managed conditions.〔 * At the level of genetic testing, its heredity will show a degree of integrity,〔 but still some genetic heterogeneity〔 (i.e. genetic diversity).〔〔 Not every source on the topic enumerates each of these criteria, and they may be weighted differently depending on a given source's focus (e.g., governmental regulation, biological sciences, agribusiness, anthropology and culture, environmental conservation, pet keeping and breeding, etc.). Additionally, not all cultivars agreed to be landraces exhibit all possible landrace characteristics.〔 Plant landraces have been the subject of more intensive study, and the majority of the academic literature about landraces is focused on agricultural botany, not animal husbandry. Most plant landraces are associated with traditional agricultural systems. While many landrace animals are associated with farming, other domestic animals have been put to use as modes of transportation, as companion animals, for sporting purposes, and for other non-farming uses, so their geographic distribution may differ. For example, horse landraces are less common because human use of them for transport has meant that they have moved with people more commonly and constantly than most other domestic animals, reducing the incidence of populations locally genetically isolated for extensive periods of time.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「landrace」の詳細全文を読む スポンサード リンク
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