Molecular basis of resistance to bensulfuron-methyl and cross-resistance patterns to ALS-inhibiting herbicides in Ludwigia prostrata

Abstract

AbstractLudwigia prostrata is a problematic weed in rice fields in China, where acetolactate synthase (ALS)-inhibiting herbicides (e.g., bensulfuron-methyl) are widely used for the management of broadleaf weeds. Recently, an L. prostrata biotype (JS-R) that failed to be controlled with ALS-inhibiting herbicides was found in Jiangsu Province, China. This study aims to determine the level and molecular mechanism of resistance to bensulfuron-methyl in this JS-R biotype and to evaluate its spectrum of cross-resistance to other ALS-inhibiting herbicides. The dose–response assays indicated that the JS-R L. prostrata biotype had evolved 21.2-fold resistance to bensulfuron-methyl compared with the susceptible biotype (JS-S). ALS gene sequencing revealed that a nucleotide mutation (CCA to TCA) at codon 197, resulting in a Pro-197-Ser mutation, was detected in the resistant plants. Moreover, while the JS-R biotype contained the Pro-197-Ser resistance mutation and showed cross-resistance to pyrazosulfuron-ethyl (12.0-fold), it was sensitive to penoxsulam, bispyribac-sodium, and imazethapyr, which may serve as alternative herbicides to control the resistant L. prostrata biotype. This is the first confirmation of an L. prostrata biotype resistant to bensulfuron-methyl due to a Pro-197-Ser resistance mutation in the ALS gene.