QYR301, 1,3-Dimethyl-1H-pyrazole-4-carboxylic acid 4-[2-chloro-3-(3,5-dimethyl-pyrazol-1-ylmethyl)-4-methanesulfonyl-benzoyl]-2,5-dimethyl-2H-pyrazol-3-yl ester, is a novel HPPD-inhibiting herbicide and was evaluated to provide a reference for post-emergence (POST) application under greenhouse and field conditions. The crop safety (180 and 360 g active ingredient (a.i.) ha⁻¹ treatments) experiment revealed that wheat, paddy, garlic and corn were the only four crops without injury at both examined herbicide rates. The weed control efficacy (60 and 120 g a.i. ha⁻¹) experiment showed that QYR301 exhibited high efficacy against many weeds, especially weeds infesting paddy fields. Furthermore, it is interesting that both susceptible and multiple herbicide resistant Echinochloa crus-galli (L.) Beauv. and Echinochloa phyllopogon (Stapf) Koss, two notorious weed species in paddy field, remained susceptible to QYR301. Further crop tolerance results indicated that 20 tested paddy hybrids displayed different levels of tolerance to QYR301, with the japonica paddy hybrids having more tolerance than indica paddy hybrids under greenhouse conditions. Results obtained from field experiments showed that QYR301 POST at 135 to 180 g a.i. ha⁻¹ was recommended to provide satisfactory full-season control of E. crus-galli and Leptochloa chinensis (L.) Nees and to maximize rice yields. These findings indicate that QYR301 possesses great potential for the management of weeds in paddy fields.

Understanding the mechanism of herbicide resistance is fundamental for designing sustainable weed control strategies and exploiting herbicides rationally. Shortawn foxtail is a problem grass weed infesting several important crops in China. The repeated use of acetyl-CoA carboxylase (ACCase)-inhibiting herbicides has resulted in herbicide resistance in this weed. The ACCase gene of resistant individuals of a shortawn foxtail population (JSLS-1) has an Ile-2041-Thr mutation. F₂ generation seeds, originated from the same heterozygous plant, were harvested, and two homozygous mutant (JSLS-1RR) and wild (JSLS-1SS) populations for the Ile-2041-Thr mutation were obtained. In whole plants, the JSLS-1RR population conferred high resistance to fenoxaprop and clodinafop, moderate resistance to haloxyfop, low resistance to pinoxaden, and no obvious resistance to clethodim and sethoxydim, compared with JSLS-1SS and a proven susceptible population (HNXY-1). A derived cleaved amplified polymorphic sequence (dCAPS) marker was developed to rapidly detect the rare Ile-2041-Thr mutation in the shortawn foxtail population. This is the first report of the cross-resistance pattern of Ile-2041-Thr mutation, and the robust dCAPS marker could quickly detect this mutation in shortawn foxtail.