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.

Information on seed germination and emergence ecology of Aegilops tauschii is scant, despite it being a widespread invasive weed in China. We conducted this study to determine the effects of various factors on seed germination and seedling emergence in three A. tauschii populations. Seeds germinated across a wide range of temperatures (5–35°C), with germination of over 90% at 15–20°C. Germination was completely inhibited when dry seeds were exposed to a temperature of 160°C for 5 min; a similar response was observed for pre‐soaked seeds at 100°C. Light was neither required for nor inhibited germination. Germination was not significantly affected by pH. Aegilops tauschii was relatively tolerant to low osmotic potential and high salt stress: over 80% of seeds germinated at −0.3 MPa, and all three populations germinated in the presence of 400 mM salt (NaCl) although salt tolerance varied among the populations. Seeds buried at depths of 1–3 cm emerged well, but emergence was completely inhibited at depths greater than 8 cm. The addition of maize straw caused a linear reduction in seedling emergence, although the rate of reduction varied among the populations. The results of this study have contributed to understanding the requirements of A. tauschii germination and emergence and optimising an integrated management system for this weed in Huang–Huai–Hai Plain of China. In addition, our study provides data for development of models to predict the geographical distribution of this weed.

311Redroot pigweed (Amaranthus retroflexus L.) is a troublesome weed infesting soybean (Glycine max [L.] Merr.) productions in China. One redroot pigweed population, collected from Heilongjiang (HLJ) Province, China, was suspected to be resistant to thifensulfuronmethyl and fomesafen. The other one redroot pigweed population, collected from Shandong (SD) Province, was susceptible. The study aimed to characterize the level of thifensulfuron-methyl and fomesafen resistance using HLJ population and identify the potential resistance mechanisms to thifensulfuron-methyl. The sensitivity to other herbicides with and without the same target site was also evaluated. Acetolactate synthase (ALS) gene sequencing revealed that Trp 574 Leu or Ala 205 Val amino acid substitution were present in the HLJ population. Whole-plant herbicide bioassays showed that, compared with SD population, HLJ population displayed high level of resistance to thifensulfuron-methyl and moderate resistance to fomesafen. The 50% growth reduction (GR 50 ) value of thifensulfuron-methyl with malathion pretreatment was reduced by 23%, suggesting that both target-site resistance and non-target-site resistance mechanisms were present in thifensulfuron-methyl resistance of redroot pigweed. Cross-resistant patterns showed that the HLJ population evolved resistance to pyrithiobac-sodium, pyroxsulam, imazethapyr and fluoroglycofen, but susceptible to bentazone.Key words: Acetolactate synthase, gene mutation, protoporphyrinogen oxidase, multiple resistance. ABSTRACTMultiple resistance to thifensulfuronmethyl and fomesafen in redroot pigweed (Amaranthus retroflexus L.) from China

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