Oryza (weeds)

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Oryza rufipogon (click on image to enlarge it)
Source: Florida Department of Agriculture and Consumer Services
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Oryza (weeds) - (weedy rice, red rice)

There are different weedy and wild forms of the genus Oryza which grow in rice fields and cause serious yield losses worldwide. In general, they are morphologically similar to rice plants, but are often taller (up to several metres high) with a red pericarp and fewer seeds. They grow faster than the planted rice and may hybridize with cultivated rice. Weedy rice is often introduced into the rice fields through the seeds and is particularly a problem if rice is sown rather than transplanted. The weeds persist in the fields because of the long dormancy of their seeds which may germinate after years. Management options include the use of certified red-rice-free seeds and/or a combination of preplant herbicide applications, extended flooding and crop rotation.

Vernacular names
• Deutsch: wilder roter Reis
• English: weedy rice
red rice
common wild rice
• Español: arroz rojo
• Français: riz rouge sauvage
• Português: arroz-vermelho

Because of the close relationship between weedy and cultivated rice there is substantial gene flow between both. There is concern that with the increasing use of herbicide resistant rice cultivars, herbicide resistant weedy rice will become a major problem (Craig et al., 2014). In 2011, around 60% of rice grown in southern states of the U.S.A. were herbicide resistant.

Weedy rice is often Oryza rufipogon Griff., but may also belong to various other species, subspecies and varieties, for example:
Oryza barthii
Oryza longistaminata
Oryza nivara
Oryza punctata
Oryza sativa f. spontanea
Oryza sativa var. indica
Oryza sativa var. japonica
Oryza sativa var. sylvatica