Glyphosate‐resistant Italian ryegrass (Lolium multiflorum) on rice paddy levees in Japan |
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| Authors: | Yuki Niinomi Mutsuhiro Ikeda Masayuki Yamashita Yoshiki Ishida Motoaki Asai Yoshiko Shimono Tohru Tominaga Hitoshi Sawada |
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| Institution: | 1. Faculty of Agriculture, Shizuoka University, , Shizuoka, Japan;2. Shizuoka Prefectural Research Institute of Agriculture and Forestry, , Iwata, Japan;3. National Agricultural Research Organisation Agricultural Research Center, , Tsukuba, Japan;4. Graduate School of Agriculture, Kyoto University, , Kyoto, Japan |
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| Abstract: | The rapid range expansion of naturalized Italian ryegrass (Lolium multiflorum Lam.) in farmland is a serious problem in Fukuroi city in Shizuoka Prefecture, Japan. Glyphosate has been used to control Italian ryegrass in the levees of rice paddy fields and wheat fields for ～20 years, but this weed in Fukuroi city is poorly controlled by glyphosate. In order to elucidate the level of resistance to glyphosate in Italian ryegrass populations, seed bioassays and a foliar application experiment, using seeds collected from 16 wild populations in and around Fukuroi city and from three susceptible cultivars, were conducted. For the susceptible cultivars and one population from a site where glyphosate had not been applied for >10 years, the shoot length in the seed bioassays was greatly suppressed at a glyphosate concentration of 10 mg ai L?1 and no seedling survived after the foliar application of glyphosate at a rate of 2.3 kg ai ha?1. Nine wild populations from levees in the southern part of Fukuroi city showed vigorous shoot growth at a glyphosate concentration of 10 mg ai L?1 and had at least a 78% survival rate after the application of glyphosate at 2.3 kg ai ha?1. Four wild populations from levees in the northern part of Fukuroi city showed a slight suppression of the shoot growth as a result of the glyphosate treatment and their survival rates ranged from 20 to 64%. The results suggested that resistance to glyphosate has evolved in the wild populations of Italian ryegrass that are growing on the levees. This is the first report of a glyphosate‐resistant weed in Japan. |
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| Keywords: | glyphosate resistance Italian ryegrass seed bioassay shoot length whole plant bioassay |
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