02873naa a2200313 a 450000100080000000500110000800800410001902400380006010000140009824501500011226000090026250001220027152017420039365000100213565300140214565300200215965300270217965300250220665300260223165300310225765300390228865300090232770000180233670000190235470000160237370000150238970000230240477301320242710623112021-07-15       2021    bl uuuu     u00u1 u    #d7 a10.1016/j.pestbp.2021.1049182DOI1 aCUTTI, L.  aNegative cross-resistance to clomazone in imazethapyr-resistant Echinochloa crus-galli caused by increased metabolization.h[electronic resource]  c2021  aArticle history: Received 13 February 2021/ Revised 21 June 2021/Accepted 8 July 2021/ Available online 12 July 2021.  aAbstract: Herbicide resistance is frequently reported in E. crus-galli globally with target and non-target site resistance mechanism to acetolactate synthase (ALS)-inhibiting herbicides. However, resistance to certain herbicides can result in increased sensitivity to other herbicides, a phenomenon called negative cross-resistance. The objective of this study is to identify the occurrence of negative cross-resistance (NCR) to the pro-herbicide clomazone in populations of E. crus-galli resistant to ALS inhibitors due to increased metabolization. Clomazone dose-response curves, with and without malathion, were performed in imazethapyr-resistant and -susceptible E. crus-galli biotypes. CYPs genes expression and antioxidant enzymes activity were also evaluated. The effective dose to reduce 50% (ED50) of dry shoot weight obtained in the clomazone dose-response curves of the metabolic based imazethapyr-resistant and -susceptible biotypes groups were 22.712 and 58.745 g ha−1, respectively, resulting in a resistance factor (RF) of 0.37, indicating the occurrence of NCR. The application of malathion prior to clomazone increased the resistance factor from 0.60 to 1.05, which indicate the reversion of the NCR. Some CYP genes evaluated were expressed in a higher level, ranging from 2.6?9.1 times according to the biotype and the gene, in the imazethapyr-resistant than in -susceptible biotypes following clomazone application. Antioxidant enzyme activity was not associated with NCR. This study is the first report of NCR directly related to the mechanism of resistance increased metabolization in plants. The occurrence of NCR to clomazone in E. crus-galli can help delay the evolution of herbicide resistance.  aARROZ  aClomazone  aCytP450 enzymes  aEchinochloa crus-galli  aHerbicide activation  aIncreased sensitivity  aNon-target site resistance  aResistencia cruzada negativa (NCR)  aRICE1 aRIGON, C.A.G.1 aKASPARY, T. E.1 aTURRA, G.M.1 aMARKUS, C.1 aMEROTTO JUNIOR, A.  tPesticide Biochemistry and Physiology, July 2021, 104918. [Article in Press]. Doi: https://doi.org/10.1016/j.pestbp.2021.104918