Tolerance of Southern US Rice Cultivars to Benzobicyclon

Abstract

Benzobicyclon is the first 4-hydroxyphenylpyruvate dioxygenase-inhibiting herbicide pursued for commercial registration in U.S. rice production. A study was conducted in 2015 and 2016 to evaluate the response of eight rice cultivars to post-flood application timings of benzobicyclon at 494 g ai ha-1(proposed 2X rate). ‘Caffey’, ‘CL151’, ‘CLXL745’, ‘Jupiter’, ‘LaKast’, ‘Mermentau’, ‘Roy J’, and ‘XL753’ were evaluated in response to applications of benzobicyclon. The highest level of visible injury was observed in LaKast at 7% in 2015. No visible injury was detected among other cultivars either year at 2 weeks after treatment. In 2015 and 2016, no more than a four-day delay to reach 50% heading occurred across all cultivars. Rough rice yield was not affected by any of the post-flood application timings of benzobicyclon. A second study was conducted in 2016 at three locations throughout Arkansas to investigate the tolerance of 19tropical japonica(inbred and hybrid) and twoindicainbred cultivars to a premix containing benzobicyclon at 494 g ai ha-1and halosulfuron at 72 g ai ha-1 applied 1 week after flooding. Thetropical japonicacultivars have excellent crop safety to benzobicyclon while application to theindicacultivars, Rondo and Purple Marker, expressed severe phytotoxicity. Benzobicyclon caused less than a 2 d delay in heading to thejaponicacultivars. Rough rice yield of thetropical japonicacultivars was not affected by benzobicyclon while yields of bothindicacultivars were negatively affected. Benzobicyclon can safely be applied to drill-seededtropical japonicainbred and hybrid cultivars in a post-flood application without concerns for crop injury. Benzobicyclon should not be used onindicacultivars as it will cause severe injury, delayed heading, and yield loss.

Benzobicyclon efficacy is affected by plant growth stage, HPPD Inhibitor Sensitive 1 (HIS1) expression and zygosity in weedy rice (Oryza sativa)

“…As predicted, his1/his1 accessions/cultivars were highly sensitive to benzobicyclon at 371 g ha −1 regardless of growth stage, and predominantly HIS1 accessions or HIS1/HIS1 cultivars (e.g., LaKast) at the ≥5-leaf growth stage were tolerant. These statements are supported by evidence in the literature (Akasaka et al 2011;Kwon et al 2012;Lv et al 2021;Maeda et al 2019;Young et al 2017). For HIS1/his1 accessions/cultivars, the model predicted severe suppression to complete control at ≤2-leaf growth stage, which was observed at the Pine Tree location, but the model would indicate greater control at the 5-leaf growth stage.…”

Benzobicyclon Activity on Common Louisiana Rice Weeds

“…Ducksalad control was 79% to 93% when treated with benzobicyclon at 246 to 1,232 g ha –1 (Table 2). Young et al (2016) observed 99% control of ducksalad, California arrowhead ( Sagittaria montevidensis Cham. & Schltdl.…”

Rice tolerance to multiple applications of florpyrauxifen‐benzyl alone and followed by benzobicyclon

“…Applications of benzobicyclon alone never resulted in more than 4% visible injury to rice, whereas visible injury following florpyrauxifen-benzyl alone ranged from 4 to 27% (Table 5). All lines tested for sensitivity in this study were not in possession of the HPPD inhibitor sensitive 1 gene; therefore, minimal injury was expected from a stand-alone application of benzobicyclon (Kwon et al, 2012;Young et al, 2017).…”

“…Tolerance to benzobicyclon is known to differ between rice cultivars of japonica and indica origin (Kwon et al., 2012). Cultivars of japonica origin show little to no injury after application, whereas those of indica descent show as much as 98% injury 6 wk after application, with eventual death in some instances (Kwon et al., 2012; Young et al., 2017). Cultivar tolerance to benzobicyclon has been attributed to the presence of the HPPD inhibitor sensitive 1 gene, which is commonly found in cultivars of indica descent (Maeda et al., 2019).…”