Screening, dose-response, and management of Echinochloa crus-galli biotypes to bispyribac- sodium: Implications for histophysiological characteristics, agronomic attributes, and amylose in irrigated rice

The presence of barnyardgrass negatively affects productivity in irrigated rice. Although farmers predominantly used the bispyribac-sodium herbicide, prolonged application has inadvertently led to resistance, making it necessary to assess resistance levels for guided control strategies that combine herbicides with different modes of action (MoA). Therefore, this study aimed to (1) determine the resistance index of barnyardgrass to bispyribac-sodium herbicide, (2) identify active ingredients (a.i.) in mixed herbicides for controlling resistant barnyardgrass biotype and to evaluate the effects on histophysiological, agronomic attributes, and amylose content in irrigated rice. The experiment started by collecting barnyardgrass seeds from five accessions in irrigated rice fields, and then sprayed with the bispyribac-sodium at the recommended dose (103 g a.i.ha ^− 1 ) from April to July 2023. The seeds in the resistant category were continued in dose-response testing at 0, 1/16, 1/8, 1/4, 1/2, 1, 2, 4, 8, and 16-fold the recommended dose from August to November 2023. Biotype progenies from low, labeled, and high-doses were further evaluated for resistance management using cyhalofop-butyl+penoxsulam, florpyrauxifen-benzyl+cyhalofop-butyl, fenoxaprop-P-ethyl+ethoxysulfuron, and bentazone+MCPA at the recommended dose from July to December 2024. Parameters were observed and analyzed by ANOVA and DMRT. The results showed that the SB3-accession was 9.82-fold more resistant to the bispyribac-sodium herbicide compared to the susceptible. The fenoxaprop-P-ethyl+ethoxysulfuron demonstrated 100% effectiveness in controlling barnyardgrass of resistant biotype progenies, thereby increasing irrigated rice productivity and amylose content were 27.01 and 31.50%. In conclusion, this study achieved effective management of resistant-biotype by combination of herbicides with different MoA.