02960naa a2200217 a 450000100080000000500110000800800410001910000220006024501630008226000090024552021920025465300220244665300250246865300270249370000180252070000220253870000160256070000140257670000220259077301300261211253012016-08-17       2016    bl uuuu     u00u1 u    #d1 aMARTINS, B. A. B.  aQuinclorac Absorption and Translocation in Cross and Multiple Resistant Barnyardgrass (Echinochloa crus-galli) Populations from Brazil.h[electronic resource]  c2016  aIn rice fields from South Brazil, Echinochloa crus-galli has become a difficult-to-control species since the first population was reported as multiple resistant to ALS inhibitors and synthetic auxins. E. crus-galli populations (ECH77 and ECH141) cross-resistant to imazethapyr and bispiribac-sodium and resistant to quinclorac were used to study mechanisms of quinclorac resistance. Population ECH141 is resistant to the ACCase inhibitor cyhalofop-butyl. Absorption and translocation of [14C]quinclorac in ECH77, ECH141 and in a susceptible (SUS) biotype were determined. Maximum absorption was estimated to occur at 48 HAT for SUS, compared to 54 and 57 HAT for ECH77 and ECH141, respectively. Time required for 90% of maximum absorption (t90) was estimated in 29 and 34 HAT for ECH77 and ECH141, respectively, while for SUS, t90 was 10 HAT. At 72 HAT, more [14C] remained in the treated leaf of SUS (47% of total absorbed) compared to ECH77 and ECH141 (27% and 23% of total absorbed, respectively). Translocation was predominantly below the treated leaf in SUS throughout the experiment, with less than 1% and 0.5% of [14C] detected above the treated leaf and in the root, respectively. At 48 HAT, 6%, 13% and 10% of absorbed [14C] had been translocated below the treated leaf in SUS, ECH77 and ECH141, respectively. At the same evaluation time, 1%, 9% and 14% of absorbed [14C] had been translocated above the treated leaf in SUS, ECH77 and ECH141, respectively. At 48 and 72 HAT, less than 0.5% of [14C] was detected in the roots of the resistant biotypes. Levels of [14C] increased not only below but also above the treated leaf of ECH141 throughout the experiment. At 72 HAT, 15% and 17% of [14C] was detected below and above the treated leaf of ECH141, respectively. The greater total translocation in ECH77 and ECH141 compared to SUS, the [14C] distribution pattern across plant parts, as well as cross and multiple resistance present in ECH77 and ECH141, lead to the hypotheses: 1) the greater [14C] translocation in the resistant biotypes might be [14C]quinclorac metabolites, and 2) resistance is, therefore, primarily metabolism-based. Metabolism studies are being conducted.  aauxinic herbicide  ametabolic resistance  aradiolabeled herbicide1 aNOLDIN, J. A.1 aTORNISIELO, V. L.1 aREIS, F. C.1 aKARAM, D.1 aMALLORY-SMITH, C.  tIn: INTERNATIONAL WEED SCIENCE CONGRESS, 7., 2016, Prague, Czech Republic. Proceedings... Prague, Czech Republic: IWSS, 2016.