Toxicity and selective mechanism of imazamox by weedy rice and imidazolinone‐resistant rice in China

Abstract

Weedy rice (Oryza spp.) is a notorious weed in direct‐seeding paddy fields. Because it has anatomical and physiological traits similar to those of cultivated rice, no selective herbicide is effective in controlling weedy rice growing among conventional rice cultivars. Imidazolinone (IMI)‐resistant rice lines JD372 and JJ818 have been planted with imazamox to control weedy rice in Jiangsu and Shanghai, China. Whole‐plant dose–response analysis showed that imazamox exhibited high efficacy against three populations of weedy rice. The ED90 of weedy rice populations FN‐5, GY‐8, and HY‐3 were 46.87, 61.43, and 52.17 g a.i. ha−1, respectively, close to the recommended field dose (50 g a.i. ha−1) of imazamox. Conversely, the ED10 values of JD372 and JJ818 were slightly lower than 50 g a.i. ha−1. These findings indicate that imazamox can control weedy rice production in JD372 and JJ818 fields. The acetolactate synthase (ALS) sensitivity of JD372 in vitro was 1714.89‐fold lower to imazamox than was that of FN‐5. ALS gene sequencing revealed a Ser653Asn point mutation—a common mutation that confers resistance to IMI herbicides in JD372. In addition, higher ALS expression levels in JD372 were found at 24 and 72 h after imazamox treatment. ALS overexpression might partially compensate for the ALS activity of JD372 that was suppressed by imazamox.

Increases in Genetic Diversity of Weedy Rice Associated with Ambient Temperatures and Limited Gene Flow

“…China has a long history of rice cultivation, and weedy rice infestation of rice fields is a continued problem for rice production [27][28][29]. In the typical tropic rice cultivation regions, such as the Guangdong, Guangxi, and Hainan Provinces, rice is cultivated for two seasons, namely the early-and late rice-cultivation seasons.…”

“…As an efficient molecular tool to estimate genetic diversity in plant populations, SSR fingerprinting has been extensively used in estimating genetic diversity, differentiation, and structures of weedy rice populations effectively [14,24,[31][32][33][34]. China has a long history of rice cultivation, and weedy rice infestation of rice fields is a continued problem for rice production [27][28][29]. In the typical tropic rice cultivation regions, such as the Guangdong, Guangxi, and Hainan Provinces, rice is cultivated for two seasons, namely the early-and late rice-cultivation seasons.…”

Review of the Occurrence of Herbicides in Environmental Waters of Taihu Lake Basin and Its Potential Impact on Submerged Plants

“…However, they are ineffective against Poaceae weeds. Quinclorac has a special effect in killing barnyard grasses in rice fields [58,59]. Usually, herbicides are only applied once per crop of rice.…”