''Oryza'' is a
genus
Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...
of plants in the
grass family. It includes the major food crop
rice
Rice is a cereal grain and in its Domestication, domesticated form is the staple food of over half of the world's population, particularly in Asia and Africa. Rice is the seed of the grass species ''Oryza sativa'' (Asian rice)—or, much l ...
(species ''
Oryza sativa'' and ''
Oryza glaberrima''). Members of the genus grow as tall,
wetland
A wetland is a distinct semi-aquatic ecosystem whose groundcovers are flooded or saturated in water, either permanently, for years or decades, or only seasonally. Flooding results in oxygen-poor ( anoxic) processes taking place, especially ...
grasses, growing to tall; the genus includes both
annual and
perennial
In horticulture, the term perennial ('' per-'' + '' -ennial'', "through the year") is used to differentiate a plant from shorter-lived annuals and biennials. It has thus been defined as a plant that lives more than 2 years. The term is also ...
species.
''Oryza'' is situated in tribe
Oryzeae
Oryzeae is a Tribe (biology), tribe of flowering plants in the true grass family, Poaceae. It contains 11 genera, including both cultivated rice (''Oryza'') and wild rice (''Zizania'').
Genera
There are 11 genera classified in two subtribes:
...
, which is characterized morphologically by its single-flowered spikelets whose
glumes are almost completely suppressed. In ''Oryza'', two sterile
lemma simulate glumes. The tribe Oryzeae is in subfamily Ehrhartoideae,
a group of Poaceae tribes with certain features of internal leaf anatomy in common. The most distinctive leaf characteristics of this subfamily are the arm cells and fusoid cells found in their leaves.
[Heywood, V.H. Flowering Plants of the World 1993 Oxford University Press]
One species, Asian rice (
''O. sativa''), provides 20% of global grain and is a food crop of major global importance. The species are divided into two subgroups within the genus.
Species
Inside the genus ''Oryza'', species can be divided by their genomes types (listed after each species name below). They include the
diploid
Ploidy () is the number of complete sets of chromosomes in a cell, and hence the number of possible alleles for autosomal and pseudoautosomal genes. Here ''sets of chromosomes'' refers to the number of maternal and paternal chromosome copies, ...
(2n = 24) of cultivated rice and
their relatives, , , , and as well as the
tetraploid (4n = 48) , , , and . Species of the same genome type cross easily, while hybridizing different types requires techniques like
embryo rescue.
Over 300 names have been proposed for species, subspecies, and other infraspecific taxa within the genus. Published sources disagree as to how many of these should be recognized as distinct species. The following follows the World Checklist maintained by Kew Garden in London.
# ''
Oryza australiensis'' (EE) – Australia
# ''
Oryza barthii'' (AA) – tropical Africa
# ''
Oryza brachyantha'' (FF) – tropical Africa
# ''
Oryza coarctata'' (KKLL) – India, Pakistan, Bangladesh, Myanmar
# ''
Oryza eichingeri'' (CC) – tropical Africa, Sri Lanka
# ''
Oryza glaberrima'' (AA) – African rice – tropical Africa
# ''
Oryza grandiglumis'' (CCDD) – Brazil, Venezuela, Fr Guiana, Colombia, Peru, Bolivia
# ''
Oryza latifolia'' (CCDD) – Latin America + West Indies from Sinaloa + Cuba to Argentina
# ''
Oryza longiglumis'' (HHJJ) – New Guinea
# ''
Oryza longistaminata'' (AA) – Madagascar, tropical + southern Africa
# ''
Oryza meyeriana'' (GG) – China, Indian Subcontinent, Southeast Asia
# ''
Oryza minuta'' (BBCC) – Himalayas, Southeast Asia, New Guinea, Northern Territory of Australia
# ''
Oryza neocaledonica'' (GG) – New Caledonia
# ''
Oryza officinalis'' (CC) – China, Indian Subcontinent, Southeast Asia, New Guinea, Australia
# ''
Oryza punctata'' (BB) – Madagascar, tropical + southern Africa
# ''
Oryza ridleyi'' (HHJJ) – Southeast Asia, New Guinea
# ''
Oryza rufipogon'' (AA) – brownbeard or red rice – China, Indian Subcontinent, Southeast Asia, New Guinea, Australia
# ''
Oryza sativa'' (AA) – Asian rice – China, Indian Subcontinent, Japan, Southeast Asia; naturalized many places
# ''
Oryza schlechteri'' (HHKK) – New Guinea
Formerly included
Many species are now regarded as better suited to other genera:
[
*'' Echinochloa''
*'' Leersia''
*'' Maltebrunia''
*'']Potamophila
''Potamophila'' is a genus of Australian plants in the Poaceae, grass family.
The only known species is ''Potamophila parviflora''.Ge, S., et al. (2002)A phylogeny of the rice tribe Oryzeae (Poaceae) based on matK sequence data.''American Journ ...
''
*'' Prosphytochloa''
*'' Rhynchoryza''
See also
* Specialized metabolism in ''Oryza''
References
{{Authority control
Poaceae genera
Taxa named by Carl Linnaeus