triticale

Triticale (; × ''Triticosecale'') is a hybrid of wheat (''Triticum'') and rye (''Secale'') first bred in laboratories during the late 19th century in Scotland and Germany. Commercially available triticale is almost always a second-generation hybrid, i.e., a cross between two kinds of primary (first-cross) triticales. As a rule, triticale combines the yield potential and grain quality of wheat with the disease and environmental tolerance (including soil conditions) of rye. Only recently has it been developed into a commercially viable crop. Depending on the cultivar, triticale can more or less resemble either of its parents. It is grown mostly for forage or fodder, although some triticale-based foods can be purchased at health food stores and can be found in some breakfast cereals.

When crossing wheat and rye, wheat is used as the female parent and rye as the male parent (pollen donor). The resulting hybrid is sterile and must be treated with colchicine to induce polyploidy and thus the ability to reproduce itself.

The primary producers of triticale are Poland, Germany, Belarus, France and Russia. In 2014, according to the Food and Agriculture Organization (FAO), 17.1 million tons were harvested in 37 countries across the world.

The triticale hybrids are all amphidiploid, which means the plant is diploid for two genomes derived from different species. In other words, triticale is an allotetraploid. In earlier years, most work was done on octoploid triticale. Different ploidy levels have been created and evaluated over time. The tetraploids showed little promise, but hexaploid triticale was successful enough to find commercial application.

The International Maize and Wheat Improvement Center (CIMMYT) triticale improvement program was intended to improve food production and nutrition in developing countries. Triticale was thought to have potential in the production of bread and other food products, such as cookies, pasta, pizza dough and breakfast cereals. The protein content is higher than that of wheat, although the glutenin fraction is less. The grain has also been stated to have higher levels of lysine than wheat. Acceptance would require the milling industry to adapt to triticale, as the milling techniques employed for wheat are unsuited to triticale.Sell, J.L.; Hodgson, G.C.; Shebeski, L.H. (1962
''Triticale'' as a potential component of chick rations
Canadian Journal of Animal Science, Volume 42, Number 2 Past research indicated that triticale could be used as a feed grain and, particularly, later research found that its starch is readily digested.Bird, S. H; Rowe, J. B.; Choct, M.; Stachiw, S.; Tyler, P.; Thompson, R. D. (1999
In vitro fermentation of grain and enzymatic digestion of cereal starch
Recent Advances in Animal Nutrition, Vol 12, pp. 53–61 As a feed grain, triticale is already well established and of high economic importance. It has received attention as a potential energy crop, and research is currently being conducted on the use of the crop's biomass in bioethanol production.

History

In the 19th century, crossing cultivars or species became better understood, allowing the controlled hybridization of more plants and animals. Semen could be taken from a male of one animal species to fertilize a female from another species that wouldn't mate with the male directly, and crops plants such as wheat or rye could more systematically be hybridized with each other.

In 1873, Alexander Wilson first managed to manually fertilize the female organs of wheat flowers with rye pollen (male gametes), but found that the resulting plants were sterile, much the way the offspring of a horse and donkey is an infertile mule. Fifteen years later in 1888, a partially-fertile hybrid was produced by , "Tritosecale Rimpaui Wittmack". Such hybrids only germinate when the chromosomes spontaneously double.

Unfortunately, "partially fertile" was all that was produced until 1937, when it was discovered that the chemical colchicine, which is used both for general plant germination and on humans with gout, would force chromosome doubling by keeping them from pulling apart during cell division.

Triticale then was viable, though at that point the cost of producing the seeds was disproportionate to the yield.

By the 1960s, triticale was being produced that was far more nutritious than normal wheat. However, it was a poorly-producing crop, sometimes yielding shriveled kernels, germinating poorly or prematurely, and did not bake well.

Modern triticale has overcome most of these problems, after decades of additional breeding and gene transfer with wheat and rye. Millions of acres of the crop are grown around the world, slowly increasing toward becoming a significant source of food-calories.

Species

Triticale hybrids are currently classified by ploidy into three nothospecies:
* × ''Triticosecale semisecale'' (Mackey) K.Hammer & Filat. – tetraploid triticale. Unstable, but used in breeding bridging. Includes the following crosses:
** ''Triticum monococcum'' × ''Secale cereale'', genome AARR;
** Alternative crosses, genome ABRR (mixogenome A/B).
* × ''Triticosecale neoblaringhemii'' A.Camus – hexaploid triticale. Stable, currently very successful in argiculture. May be produced by ''Secale cereale'' × '' Triticum turgidum'', genome AABBRR.
* × ''Triticosecale rimpaui'' Wittm. – octaploid triticale. Not completely stable, mainly historical importance. May be produced by ''Secale cereale'' × '' Triticum aestivum'', genome AABBDDRR.

The current treatment follows the Mac Key 2005 treatment of ''Triticum'' using a broad species concept based on genome composition. Traditional classifications used a narrow species concept based on the treatment of wheats b Dorofeev et al. 1979, and hence produced many more species names. The genome notation follows , with the rye genome notated as R.

Biology and genetics

Earlier work with wheat-rye crosses was difficult due to low survival of the resulting hybrid embryo and spontaneous chromosome doubling. These two factors were difficult to predict and control. To improve the viability of the embryo and thus avoid its abortion, ''in vitro'' culture techniques were developed (Laibach, 1925). Colchicine was used as a chemical agent to double the chromosomes. After these developments, a new era of triticale breeding was introduced. Earlier triticale hybrids had four reproductive disorders, namely meiotic instability, high aneuploid frequency, low fertility and shriveled seed (Muntzing 1939; Krolow 1966). Cytogenetical studies were encouraged and well funded to overcome these problems.

It is especially difficult to see the expression of rye genes in the background of wheat cytoplasm and the predominant wheat nuclear genome. This makes it difficult to realise the potential of rye in disease resistance and ecological adaptation. One of the ways to relieve this problem was to produce secalotricum, in which rye cytoplasm was used instead of that from wheat.

Triticale is essentially a self-fertilizing, or naturally inbred, crop. This mode of reproduction results in a more homozygous genome. The crop is, however, adapted to this form of reproduction from an evolutionary point of view. Cross-fertilization is also possible, but it is not the primary form of reproduction.

''Sr27'' is a stem rust resistance gene which is commonly found in triticale. Originally from rye ( Imperial Rye), now () widely found in triticale. Located on the 3A chromosome arm, originally from 3R. Virulence has been observed in field by ''Puccinia graminis'' f. sp. ''secalis'' (''Pgs'') and in an artificial cross ''Pgs'' ''Puccinia graminis'' f. sp. ''tritici'' (''Pgt''). When successful, ''Sr27'' is among the few ''Sr''s that does not even allow the underdeveloped uredinia

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