Mixture Interactions of Quizalofop and Reduced Rates of Halosulfuron

A field study was conducted in 2017 and 2018 at the LSU Agricultural Center H. Rouse Caffey Rice Research Station (RRS) near Crowley, LA. to evaluate the impact of reduced rates of halosulfuron on quizalofop activity in Louisiana rice production. Halosulfuron and a prepackaged mixture of halosulfuron plus thifensulfuron were evaluated at 0, 17, 35, or 53 g ai ha−1 and 34 or 53 g ai ha−1, respectively, in a mixture with quizalofop at 120 g ai ha-1. Control of (%) of barnyardgrass and red rice as well as two non-ACCase resistant rice lines, CL-111 and CLXL-745, were recorded at 14 and 28 d after treatment (DAT). The red rice, CL-111, and CLXL-745 represented a weedy rice population. Across all species evaluated at 14 DAT, all halosulfuron and halosulfuron plus thifensulfuron containing mixtures resulted in antagonism with an observed control of 79 to 90%, compared to an expected control of 96 to 99%. At 28 DAT, all halosulfuron containing mixtures resulted in neutral interactions for barnyardgrass control. Quizalofop mixed with halosulfuron plus thifensulfuron at the lower rate of 34 g ha−1 was able to overcome the antagonism compared with the higher rate of 53 g ha−1 for barnyardgrass control at 28 DAT. Both the high and the low rate of halosulfuron plus thifensulfuron resulted in antagonistic interaction for red rice, CL-111, and CLXL-745 control at 28 DAT. This research suggests that mixing quizalofop with halosulfuron plus thifensulfuron should be avoided, especially at the higher rate of 53 g ha−1.

Mixture interactions at mammalian olfactory receptors are dependent on the cellular environment

Functional characterization of mammalian olfactory receptors (ORs) remains a major challenge to ultimately understanding the olfactory code. Here, we compare the responses of the mouse Olfr73 ectopically expressed in olfactory sensory neurons using AAV gene delivery in vivo and expressed in vitro in cell culture. The response dynamics and concentration-dependence of agonists for the ectopically expressed Olfr73 were similar to those reported for the endogenous Olfr73, however the antagonism previously reported between its cognate agonist and several antagonists was not replicated in vivo. Expressing the OR in vitro reproduced the antagonism reported for short odor pulses, but not for prolonged odor exposure. Our findings suggest that both the cellular environment and the stimulus dynamics shape the functionality of Olfr73 and argue that characterizing ORs in ‘native’ conditions, rather than in vitro, provides a more relevant understanding of ligand-OR interactions.

Mixture Interactions at Mammalian Olfactory Receptors are Dependent on the Cellular Environment

Functional characterization of mammalian olfactory receptors (ORs) remains a major challenge to ultimately understanding the olfactory code. Here, we compare the responses of the mouse Olfr73 ectopically expressed in olfactory sensory neurons using AAV gene delivery in vivo and expressed in vitro in cell culture. The response dynamics and concentration-dependence of agonists for the ectopically expressed Olfr73 were similar to those reported for the endogenous Olfr73, but the receptor failed to mediate the antagonism between its cognate agonist and several antagonists reported for the OR expressed in vitro. Expressing the OR in vitro under the same conditions of stimulation retained the reported antagonism, but it was dependent on the duration of stimulation. Our findings suggest that both the cellular environment and the stimulus dynamics shape the functionality of Olfr73 and argue that characterizing ORs in ‘native’ conditions provides the most complete understanding of ligand-OR interactions.

Herbicide Mixtures to Control Dayflowers and Drift Effect on Coffee Cultures

ABSTRACT: The dayflower species Commelina benghalensis and C. diffusa are among the main weeds in coffee crops. The purpose of this study was to evaluate the efficacy of herbicides/herbicide mixtures in controlling dayflower species and to evaluate the possible intoxication of coffee cultures, as well as the effect of mixture interactions. Two experiments were conducted, the first one in a 12 x 2 factorial arrangement with 12 herbicides/mixtures (glyphosate, glyphosate + metsulfuron-methyl, glyphosate + flumioxazin, glyphosate + 2.4-D, glyphosate + oxyfluorfen, glyphosate + carfentrazone-ethyl, metsulfuron-methyl, flumioxazin, 2.4-D, oxyfluorfen and carfentrazone-ethyl) and two dayflower species (C. benghalensis and C. diffusa) and the second one, in a 6 x 2 + 1 factorial arrangement, with six herbicides/mixtures (glyphosate, glyphosate + metsulfuron-methyl, glyphosate + flumioxazin, glyphosate + 2.4-D, glyphosate + oxyfluorfen and glyphosate + carfentrazone-ethyl) and two application forms on coffee plants (reaching 1/3 of the coffee canopy and with a protected canopy), plus a control treatment without herbicides. There was tolerance variation within the dayflower species to the tested herbicides. Commelina benghalensis was controlled by glyphosate, 2.4-D, glyphosate + 2.4-D and glyphosate + metsulfuron-methyl, while C. diffusa was controlled by 2.4-D and glyphosate mixtures by + metsulfuron-methyl, glyphosate + oxyfluorfen and glyphosate + flumioxazin. The mixture glyphosate + 2.4-D is effective in controlling dayflower, but it caused intoxication and growth reduction of the coffee. There was antagonism in the mixture glyphosate + carfentrazone-ethyl in controlling both species, as well as for glyphosate + oxyfluorfen and glyphosate + flumioxazin for C. benghalensis.