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Aegilops cylindrica
''Aegilops cylindrica'', also known as jointed goatgrass. is an annual grass seed that is part of the tribe Triticeae, along with wheat and some other cereals.〔(Biology and control of jointed goatgrass (Aegilops cylindrica), a review )〕 It is not native to the United States, however it has become a serious issue as a weed since it was introduced in the late 19th century.〔 Due to its relation to winter wheat, it is very difficult to control. Not only are the joints similar in shape and size to the seeds of winter wheat, making it difficult to remove through grain cleaning methods, the shared genetics mean that no registered herbicides are available to single out jointed goatgrass while leaving winter wheat unharmed.〔 This poses problems for farmers who have to suffer through reduced yields and poorer quality winter wheat.〔(Management effects on the incidence of jointed goatgrass inhibitory rhizobacteria )〕
== History and Distribution ==
Jointed goatgrass is a winter annual grass seed native to Southern Europe and Russia,〔(Factors affecting germination of jointed goatgrass (Aegilops cylindrica) seed )〕 however currently there are at least 23 species distributed worldwide.〔 It is considered a problem weed in United States, where it is now widely spread across western and central regions.〔〔 It entered the US at several different times and at different locations,〔 however the first was possibly in the late 19th century when Mennonite settlers from Russia brought Turkey winter wheat to Kansas.〔 The first sample of jointed goatgrass was collected in Centerville, DE in 1870 and later samples collected in 1910 showed that jointed goatgrass had escaped from experimental plots on South Dakota State University campus at Brookings, SD.〔
In 1999, it was reported that jointed goatgrass had infested an estimated 2 million hectares in the US alone, and that this was annually increasing at a rate of about 20 000 hectares.〔 In 1986, jointed goatgrass had been reported as having infected less than 1% of winter wheat fields in seven counties in Nebraska, yet it was rated one of the ten most troublesome weeds, concerning 13% of respondents to a 1984 farmer survey.〔
Human activities, wind, and machinery help to spread jointed goatgrass seeds once the joints disarticulate.〔 However, due to the size of joints, wind dispersal is not as effective at spreading jointed goatgrass.〔 Some of the human activities that helped spread jointed goatgrass include; planting contaminated wheat, allowing joints to blow from passing trucks hauling grain, transporting combines to different fields, or using straw spreaders on combines.〔 Steven Miller argued that some states did not have laws that prevented contaminated winter wheat from being certified, which helped lead to it still being planted.〔 Combines with straw spreaders are likely to spread jointed goatgrass joints farther than combines without these spreaders.〔 Also, because the joints can float, runoff from fields can take them into rivers where they can aggregate and create an infestation in moist depressions, draws in fields, or along drainageways.〔 It has been observed by growers and researchers that jointed goatgrass has a higher germination and emergence rate in compacted soils (such as in the wheel tracts of tractors) than in looser soils.〔
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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