Latin name: Hordeum vulgare
Source material: Pollen
Family: Poaceae (Gramineae)
Sub family: Pooideae
Common names: Barley, Common Barley, Barleycorn, Malt, Naked Barley, Pearl Barley, Pot Barley, Scotch Barley
Barley pollen g201 should be differentiated from Barley, the food f6.
A grass species producing pollen, which often induces hay fever, asthma and conjunctivitis in sensitised individuals.
Barley is probably native to the Middle East, from Afghanistan to northern India. It first came under cultivation 12 000 or more years ago. It is widely cultivated in temperate areas of the world for its edible seed. Because of its wide geographical distribution, Barley has accumulated a vast array of genetic variability.
Barley is the fourth most important cereal crop in the world after wheat, maize and rice. Russia is the largest producer of Barley, followed by Great Britain, France, the United States, then Canada and other countries.
Barley is an erect annual grass. Its stout, simple stem is hollow and jointed, and can grow more than a meter high. The narrow, tapering leaves ascend the stem in two ranks, with some overlapping; and their bases form loose sheaths around the stem. The flowers are hermaphrodite (have both male and female organs) and are pollinated by wind. The flowers grow in bristly-bearded terminal spikes, eventually producing the elliptic, furrowed Barley grains. The time of flowering depends on the cultivar, and cultivars include winter-hardy varieties. The period from planting to harvest varies from 60 days to four months.
Barley can be categorised into three basic types: two-rowed, with kernels in two lines; four-rowed, with kernels in four lines; and six-rowed, with kernels in six lines. Barley may also be categorised into three types based on the nature of the hulls, which may vary from tight to loose to non-existent.
Barley is not known in the wild. It may be found as a remnant of cultivation but does not persist.
Barley is a staple food in the developing world, and is used in industrialised countries for animal feed and for speciality food products. Malt is a nutritious sweetener in various foods. It is also grown for distilling malt liquors and spirits, and is one of the primary components of beer. About half of the total US Barley production is used for malting. Barley has many folk medicinal uses.
Scotch or Pot Barley is Barley with the outer husk removed. Pearl Barley is Barley rounded and polished after the husk is removed and used in cooking, to enrich soups, etc.
Barley straw is used as bedding and packing material, for making hats and for the manufacture of cellulose pulp. It is a source of fibres for making paper, and of biomass for fuel, and it may be shredded and used as mulch.
Allergens characterised to date:
Hor v 1, a 14.5 kDa protein, a Group 1 grass allergen, an expansin (1, 2).
Hor v 2, a Group 2 grass allergen (2, 3).
Hor v 4, a Group 4 grass allergen, a pectate lyase (berberine bridge enzyme) (1, 4-6).
Hor v 5, a Group 5 grass allergen, a ribonuclease, and previously known as Hor v 9 (1, 2, 7-11).
Hor v 12, a profiling (7, 12).
Hor v 13, a Group 13 grass allergen, a polygalacturonase (13, 14).
Southern blots suggest that Hor v 5 (Hor v 9) allergens exist as multiple isoforms in Barley (10).
The pantemperate tribe Triticeae is notable for its cereal genera: Wheat, Barley and Rye. Their close relation makes cross-reactivity likely between Wild Rye grass g70, Cultivated Wheat g15, Cultivated Rye grass g12, Barley g201, and Couch grass (Agropyron repens) as well as Lymegrass (Elymus arenarius). Extensive cross-reactivity among the different individual species of the genus may be expected. There should be cross-reactivity with other members of the family Poaceae, particularly in the subfamily Pooideae (Rye grass (g5), Canary grass (g71), Meadow grass (g8), Timothy (g6), Cocksfoot (g3), Meadow Fescue (g4), Velvet (g13), Redtop (g9), Meadow Foxtail (g16), Wild Rye grass (g70)) (15, 16).
The Group 4 allergens are well known as important major allergens of grasses, and may account for a degree of cross-reactivity between grass pollens containing this allergen (5).
Sequence comparisons showed that the Hor v 5 (Hor v 9) cDNA clones were also homologous to Group 5 allergens of Timothy grass (Phleum pratense) pollen and canary grass (Phalaris aquatica) pollen, and the Group 9 allergen of ryegrass (Lolium perenne) pollen(10).
The Barley pollen cDNA, and three other cloned allergens: Phl p 5, Phl p 5a (from Timothy) and Lol p 1b (from Rye grass) were demonstrated to have extensive nucleotide and amino acid sequence similarity to Poa p 9 isoallergens of Meadow grass (1).
Anecdotal evidence suggests that Barley pollen may induce asthma, allergic rhinitis and allergic conjunctivitis in sensitised individuals; however, few studies have been reported to date.
In a French study, using specific IgE tests, Barley pollen and Rye pollen were demonstrated to be the cereals that were the most prevalent sensitising allergens in children with grass pollinosis (17).
Aerobiological surveys have detected Barley pollen in the atmosphere of Madrid, Spain (18) and in the Sarajevo region (19).
Flour made from the seed of Barley may result in symptoms of food allergy, occupational allergy, or allergy reactions to beer (20-22).
Compiled by Dr Harris Steinman, developer of Allergy Advisor, http://allergyadvisor.com
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