Ploidy is the number of complete sets of chromosomes in a cell, and hence the number of possible alleles for autosomal and pseudoautosomal genes. Sets of chromosomes refer to the number of maternal and paternal chromosome copies, respectively, in each homologous chromosome pair, which chromosomes naturally exist as. Somatic cells, tissues, and individual organisms can be described according to the number of sets of chromosomes present : monoploid, diploid, triploid, tetraploid, pentaploid, hexaploid, heptaploid or septaploid, etc. The generic term polyploid is often used to describe cells with three or more sets of chromosomes.
Polyploidy is a condition in which the cells of an organism have more than one pair of (homologous) chromosomes. Most species whose cells have nuclei (eukaryotes) are diploid, meaning they have two complete sets of chromosomes, one from each of two parents; each set contains the same number of chromosomes, and the chromosomes are joined in pairs of homologous chromosomes. However, some organisms are polyploid. Polyploidy is especially common in plants. Most eukaryotes have diploid somatic cells, but produce haploid gametes by meiosis. A monoploid has only one set of chromosomes, and the term is usually only applied to cells or organisms that are normally diploid. Males of bees and other Hymenoptera, for example, are monoploid. Unlike animals, plants and multicellular algae have life cycles with two alternating multicellular generations. The gametophyte generation is haploid, and produces gametes by mitosis; the sporophyte generation is diploid and produces spores by meiosis.
Hordeum is a genus of annual and perennial plants in the grass family. They are native throughout the temperate regions of Africa, Eurasia, and the Americas.
Bromus tectorum, known as downy brome, drooping brome or cheatgrass, is a winter annual grass native to Europe, southwestern Asia, and northern Africa, but has become invasive in many other areas. It now is present in most of Europe, southern Russia, Japan, South Africa, Australia, New Zealand, Iceland, Greenland, North America and western Central Asia. In the eastern US B. tectorum is common along roadsides and as a crop weed, but usually does not dominate an ecosystem. It has become a dominant species in the Intermountain West and parts of Canada, and displays especially invasive behavior in the sagebrush steppe ecosystems where it has been listed as noxious weed. B. tectorum often enters the site in an area that has been disturbed, and then quickly expands into the surrounding area through its rapid growth and prolific seed production.
Dactylis is a genus of Eurasian and North African plants in the bluegrass subfamily within the grass family. Dactylis is native to North Africa, they are found throughout the world, and are an invasive species. They are known in English as cock's-foot or cocksfoot grasses, also sometimes as orchard grasses.
During 10,000 years of cultivation, numerous forms of wheat, many of them hybrids, have developed under a combination of artificial and natural selection. This diversity has led to much confusion in the naming of wheats. Genetic and morphological characteristics of wheat influence its classification; many common and botanical names of wheat are in current use.
Triticeae is a botanical tribe within the subfamily Pooideae of grasses that includes genera with many domesticated species. Major crop genera found in this tribe include wheat, barley, and rye; crops in other genera include some for human consumption, and others used for animal feed or rangeland protection. Among the world's cultivated species, this tribe has some of the most complex genetic histories. An example is bread wheat, which contains the genomes of three species with only one being a wheat Triticum species. Seed storage proteins in the Triticeae are implicated in various food allergies and intolerances.
Hordeum jubatum, with common names foxtail barley, bobtail barley, squirreltail barley, and intermediate barley, is a perennial plant species in the grass family Poaceae. It occurs wild mainly in northern North America and adjacent northeastern Siberia. However, as it escaped often from gardens it can be found worldwide in areas with temperate to warm climates, and is considered a weed in many countries. The species is a polyploid and originated via hybridization of an East Asian Hordeum species with a close but extinct relative of Californian H. brachyantherum. It is grown as an ornamental plant for its attractive inflorescences and when done flowering for its inflorescence.
Agropyron desertorum is a plant species in the family Poaceae which was originally from Russian and Siberian steppes until it was introduced to the United States from there between 1907 and 1913. Prior to its introduction it was believed that Desert wheatgrass and crested wheatgrass are different species. Currently it can still be found in Central and Western United States, except for Idaho, Kansas, Louisiana, Minnesota, Oklahoma, and Washington.
Hordeum murinum is a species of flowering plant in the grass family Poaceae, commonly known as wall barley or false barley. It is a close relative of cultivated barley.
Hordeum pusillum, also known as little barley, is an annual grass native to most of the United States and southwestern Canada. It arrived via multiple long-distance dispersals of a southern South American species of Hordeum about one million years ago. Its closest relatives are therefore not the other North American taxa like meadow barley or foxtail barley, but rather Hordeum species of the Pampas of central Argentina and Uruguay. It is less closely related to the Old World domesticated barley, from which it diverged about 12 million years ago. It is diploid.
A doubled haploid (DH) is a genotype formed when haploid cells undergo chromosome doubling. Artificial production of doubled haploids is important in plant breeding.
Elymus canadensis, synonyms including Elymus wiegandii, commonly known as Canada wild rye or Canadian wildrye, is a species of wild rye native to much of North America. It is most abundant in the central plains and Great Plains. It grows in a number of ecosystems, including woodlands, savannas, dunes, and prairies, sometimes in areas that have been disturbed.
Panicum decompositum, known by the common names native millet, native panic, Australian millet, papa grass, and umbrella grass, is a species of perennial grass native to the inland of Australia. It occurs in every mainland state. The seeds can be cultivated to produce flour typically used in Aboriginal bushfood. The species is also considered to have relatively high palatability by livestock, making it suitable for grazing pastures.
Barley, a member of the grass family, is a major cereal grain grown in temperate climates globally. It was one of the first cultivated grains; it was domesticated in the Fertile Crescent around 9000 BC, giving it nonshattering spikelets and making it much easier to harvest. Its use then spread throughout Eurasia by 2000 BC. Barley prefers relatively low temperatures and well-drained soil to grow. It is relatively tolerant of drought and soil salinity but is less winter-hardy than wheat or rye.
Hordeum arizonicum is a species of wild barley known by the common name Arizona barley. It is native to northern Mexico and the southwestern United States, where it grows in wet spots in desert regions, such as irrigation ditches. It can grow in somewhat saline soils. This is an annual or perennial grass forming erections 20 to 70 cm high. The inflorescence is a spike up to about 12 cm long made up of spikelets up to about 3 cm long each, usually tipped with awns.
Hordeum intercedens is a diploid, annual species of wild barley known by the common names bobtail barley and vernal barley. It is native to southern California and northern Baja California, where it is an increasingly rare member of the flora in saline and alkaline soils near seasonal waterflows and vernal pool habitats. Today most occurrences are located on the Channel Islands of California; many of the occurrences known from the mainland have been extirpated in the process of land development. This is an annual grass growing erect to bent in small tufts with stems up to 40 centimeters long. The inflorescence is a green spike up to 6.5 centimeters long made up of awned spikelets between 1 and 2 centimeters long.
Psathyrostachys juncea is a species of grass known by the common name Russian wildrye. It was formerly classified as Elymus junceus. It is native to Russia and China, and has been introduced to other parts of the world, such as Canada and the United States. Psathyrostachys juncea is a great source of food for grazing animals, as it has high nutrition value in its dense basal leaves, even in the late summer and autumn seasons. This species can grow and prosper in many harsh environments, making it an ideal candidate for improvement as it can grow in areas were farming is difficult. This species is a drought-resistant forage plant and can survive during the cool seasons. It is also a cross-pollinator and is self-sterile. This means that P. juncea cannot self-fertilize; it must find another plant of the same species with which to exchange gametes. Self-sterilization increases the genetic diversity of a species.
Dichanthium annulatum is a species of grass in the family Poaceae. It is commonly used as a forage for livestock.
Diploidization is the process of converting a polyploid genome back into a diploid one. Polyploidy is a product of whole genome duplication (WGD) and is followed by diploidization as a result of genome shock. The plant kingdom has undergone multiple events of polyploidization followed by diploidization in both ancient and recent lineages. It has also been hypothesized that vertebrate genomes have gone through two rounds of paleopolyploidy. The mechanisms of diploidization are poorly understood but patterns of chromosomal loss and evolution of novel genes are observed in the process.
