Haploidy


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Related to Haploidy: diploidy, haploids
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Haploidy

 

the opposite of polyploidy; a phenomenon that involves the multiple reduction of the number of chromosomes in the offspring in comparison to the maternal individual. Haploidy, as a rule, is the result of the development of the embryo from reduced (haploid) gametes or from cells that are functionally equivalent to gametes by means of apomixis—that is, without fertilization. Haploidy is rarely encountered in the animal world but is common among flowering plants. It has been recorded in more than 150 species of plants from 70 genera of 33 families (including plants from the families Gramineae, Solanaceae, Orchidaceae, and legumes). The phenomenon occurs in all major cultivated plants: wheat, rye, corn, rice, barley, sorghum, potatoes, tobacco, cotton, flax, beets, cabbage, pumpkins, cucumbers, and tomatoes. It also occurs in fodder grasses, including meadow grass, bromegrass, timothy, alfalfa, and vetch.

Haploidy is genetically determined and is encountered in certain species and varieties with a predictable frequency. (For example, in corn there is one haploid per 1,000 diploid plants.) In the evolution of species, haploidy provided a unique mechanism for reducing the level of ploidy. Haploidy is used in the solution of many genetic problems, including determination of the effect of a dose of a gene, obtaining aneuploids, the study of the genetics of quantitative traits, and the analysis of genomes. In the selection of plants equivalent, self-fertilized strains are obtained from the haploids by doubling the number of chromosomes of the homozygous strain. These plants are used to produce hybrid seeds (for example, in corn) as well as to transpose the selection process from the polyploid to the diploid level (for example, in potatoes). The special type of haploidy known as androgenesis, in which the sperm nucleus replaces the nucleus of the ovum, is used to obtain sterile male analogues in corn.

REFERENCES

Kirillova, G. A. “Iavlenie gaploidii u pokrytosemennykh rastenii.” Genetika, 1966, no. 2.
Gaploidiia u pokrytosemennikh rastenii, part 1. Saratov, 1970.
Kimber, G., and R. Riley. “Haploid Angiosperms.” Botanical Review, 1963, vol. 29, no. 4. Pages 480-531.
Magoon, M. L., and K. R. Khanna. “Haploids.” Caryologia, 1963, vol. 16, no. 1, pp. 191-255.

S. S. KHOKHLOV

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
As in the other two androgenic ways to haploidy, the genotype plays an important role.
Given the economic impact of these species and/or their suitability for both fundamental and applied research, parallel efforts have been made to circumvent their extreme recalcitrancy by exploring alternative pathways to androgenic haploidy, whereas in species more easily inducible to microspore embryogenesis, focusing on alternatives is unnecessary in practice, and resources can be devoted to investigate more promising ways to doubled haploidy.
Phylogenetic support for haploidy in Symbiodinium and other dinofiagellates
Given the close evolutionary relationship between the two groups, the ancestral state in the progenitor of the apicomplexans and dinoflagellates was probably haploidy.
Complete haploidy is therefore the only evolutionarily stable life cycle.
Neither haploidy nor any life cycle that retains both phases is ever stable here.
CADL 98 was developed from cultivated tetraploids via haploidy. CADL was described in 1979 (1) and research involving CADL and cultivated 4x alfalfa was reviewed (2).
Haploidy induction followed by chromosome doubling either during culture or by colchicine treatment of haploid seedlings leads to the production of doubled haploid lines.
Chapter 11 deals with self-incompatibility and pollen rejection in angiosperms, although it has little relevance in a book on haploidy.
The use of haploidy to develop plants that express several recessive traits using light-seeded canola (Brassica napus) as an example.
After root establishment, plantlets were transferred to 10-cm pots and grown to maturity to verify their haploidy through lack of seed production.
Similarly, the occurrence of parthenogenesis in tetraploid alfalfa (Bingham, 1971) is another feature which has been widely exploited to reduce cultivated tetraploid alfalfa to the diploid level via haploidy (Bingham and McCoy, 1979).