Mutations of acetolactate synthase gene and response of sulfonylurea-resistant biotypes of Sagittaria trifolia L. to several herbicides in Yamagata, Japan

Abstract

Acetolactate synthase (ALS) gene was analyzed, and the response to sulfonylurea (SU) herbicides was investigated by pot experiments with Sagittaria trifolia L. collected in Yamagata Prefecture, Northeast Japan. The results revealed that SU-resistant biotypes of S. trifolia were widely distributed in the area studied. Both target-site resistance (TSR: resistance caused by mutation of the target gene) and non-target-site resistance (NTSR: resistance not caused by mutation) were detected in the examined biotypes. The geographical distribution of TSR was different from that of NTSR. Variations were also found between the distribution of TSR with the Pro₁₉₇ mutation and that with the Trp₅₇₄ mutation, indicating that Trp₅₇₄ mutants were not ubiquitous in the area studied. In addition, pot experiments with alternative herbicides showed that pyraclonil, pyrazolate, and tefuryltrione were highly effective against both TSR and NTSR biotypes. Pyrimisulfan, which is not a SU herbicide but an ALS inhibitor, was effective against TSR with the Pro₁₉₇ mutation. However, this herbicide did not suppress the growth of TSR with the Trp₅₇₄ mutation. In conclusion, it is important that effective herbicides are adopted depending on the above different biotypes in the sequential application of different herbicides to reduce the prevalence of resistant S. trifolia weeds.