Isoxadifen-Ethyl Derivatives Protect Rice from Fenoxaprop-P-Ethyl–associated Injury during the Control of Weedy Rice

Abstract

Fenoxaprop-P-ethyl, a phenoxy herbicide of the aryloxy–phenoxy–propionic acid group, had a strong control effect when applied POST to weedy rice in this study, with the effective concentrations of 294 μM and 218 μM of herbicide causing 50% inhibition (IC50) in plant height and fresh weight values, respectively. However, fenoxaprop-P-ethyl caused phytotoxicity in cultivated rice. Isoxadifen-ethyl, a widely used herbicide safener in rice, can decrease the phytotoxicity caused by fenoxaprop-P-ethyl. Owing to the extremely similar morphological features and physiological properties of weedy and cultivated rice, it is not practical to spray isoxadifen-ethyl directly on cultivated rice plants to safen them. Applying the safener directly to cultivated rice seeds may be a practical alternative method. To improve the biological activity of isoxadifen-ethyl seed treatments, novel compounds were designed by splicing other groups, including amines, amino acids, and 2- methoxy-5-nitrophenol sodium salt, to the parental structure of isoxadifen-ethyl. Through hydrolysis, acyl chlorination, acyl amination, and esterification, a series of isoxadifen-ethyl derivatives were synthesized and their structures were determined by mass spectrometry and 1H nuclear magnetic resonance spectroscopy. The biological activities of five of the isoxadifen-ethyl derivatives, which possessed recovery effects similar to isoxadifen-ethyl, were able to relieve herbicide phytotoxicity. In pot experiments, isoxadifen-ethyl showed almost no activity as a seed treatment, while three derivative compounds, when used independently as seed treatments, were able to prevent the damage caused by fenoxaprop-P-ethyl. The results will help to develop a new control method for weedy rice, thereby decreasing production costs and increasing farmers’ incomes.

Fragmenlt Recombination Design, Synthesis, and Safener Activity of Novel Ester-Substituted Pyrazole Derivatives

“…It is a highly selective stem and leaf treatment agent. , However, due to the long-term and widespread use of FE, crops suffer varying degrees of phytotoxicity. − The application of FE results in crop yellowing, crop growth inhibition, and even crop death in serious cases. To reduce damage to crops, many methods have been reported that incorporate the scientific management of crop rotation and cultivation and the research and development of new herbicides. , In addition, the use of herbicide safeners is also considered to be an efficient solution. − …”

The safener isoxadifen‐ethyl confers fenoxaprop‐p‐ethyl resistance on a biotype of Echinochloa crus‐galli

“…22,[42][43][44] The safener isoxadifen-ethyl allows the selective use of fenoxaprop-p-ethyl in rice. 15,45 The effect of this safener occurs for multiple crops for multiple herbicide modes of action, such as rice to fenoxapropp-ethyl, 45 corn to foramsulfuron 46 and tembotrione. 47 Another safener, fenclorim, can protect rice from injury when sprayed with the herbicide pretilachlor, but it does not protect E. crus-galli.…”

“…Safener pathways of induction are not well understood, but studies suggest that they are related to cytP450, GST, glycosyl‐transferase (GT) and ABC transporter enzymes 22,42–44 . The safener isoxadifen‐ethyl allows the selective use of fenoxaprop‐ p ‐ethyl in rice 15,45 . The effect of this safener occurs for multiple crops for multiple herbicide modes of action, such as rice to fenoxaprop‐ p ‐ethyl, 45 corn to foramsulfuron 46 and tembotrione 47 .…”

Protective efficacy of phenoxyacetyl oxazolidine derivatives as safeners against nicosulfuron toxicity in maize

“…Each experiment was repeated in triplicate and a completely randomized design was used. The injury recovery rate (IRR) was calculated as follows 39 …”