Target-site basis for resistance to flucarbazone- sodium in Japanese brome (Bromus japonicus Houtt.) in China

Abstract

Japanese brome (Bromus japonicus Houtt.) is a troublesome annual weed and widely distributed in winter wheat (Triticum aestivum L.) fields in the North China Plain. A B. japonicus population (TJ06) suspected of resistance to acetolactate synthase (ALS) inhibitors was found in Tianjin, China. In this study, the TJ06 population with an Asp-376-Glu mutation in ALS gene was identified. TJ06 population developed 66.7-fold resistance to flucarbazone-sodium and exhibited obvious cross-resistance to other two ALS-inhibiting herbicides. The 50% plant growth reduction (GR50) to herbicides of pyroxsulam and mesosulfuron-methyl were 28.72 and 39.44 g ai ha -1 , respectively. In in vitro ALS activity assays, the concentration of flucarbazone-sodium required to inhibit 50% ALS activity (I50) for TJ06 was 11.3-fold greater than that for a susceptible population (TJ01), which was highly correlated with that of whole-plant response experiments and indicated that the Asp-376-Glu mutation leading to resistance reduced sensitivity of the ALS enzyme to flucarbazonesodium. Besides, one derived cleaved amplified polymorphic sequence (dCAPS) marker was designed to quickly detect Asp376 mutation in ALS gene of B. japonicus.

Distribution and Mechanism of Japanese Brome (Bromus japonicus) Resistance to ALS-Inhibiting Herbicides in China

“…For example, Pro-197 and Asp-376 mutations of the ALS gene conferring resistance to ALS inhibitors were found in many weed species, including Raphanus raphanistrum [ 25 ], Galium aparine [ 14 ], Descurainia sophia [ 30 ], Cyperus difformis [ 31 ] and Monochoria vaginalis [ 32 ]. To date, four mutations (Pro-197-Ser, Pro-197-Thr, Pro-197-Arg and Asp-376-Glu) have been reported as being related to resistance to ALS inhibitor herbicides in B. japonicus [ 3 , 4 , 5 , 6 ]. In the present study, four amino acid substitutions in the ALS gene from 17 resistant populations, including Pro-197-Ser/Thr/Phe and Asp-376-Glu, were identified by molecular analysis.…”

“…Raphanus raphanistrum with the Asp-376-Glu mutation showed high resistance to TP and SU herbicides but no resistance to imazapyr (IMI) [ 25 ]. Li et al reported that the Asp-376-Glu mutation was characterized in B. japonicus as conferring high-level resistance to pyroxsulam (TP), mesosulfuron–methyl (SU) and flucarbazone–sodium (SCT) [ 4 ]. In this study, QM21-72, QM21-76 and QM21-79 with Asp-376-Glu mutation were resistant to pyroxsulam (TP), mesosulfuron–methyl (SU) and flucarbazone–sodium (SCT).…”

“…Acetolactate synthase (ALS)-inhibiting herbicides have been used for more than 15 years to control B. japonicus in wheat fields. Recently, there have been four reports of resistance to ALS inhibitors in B. japonicus [ 3 , 4 , 5 , 6 ].…”

“…Recently, ALS inhibitor-resistant B. japonicus populations has been found in Hebei Province, Shandong Province and Tianjin municipality, and the Pro-197 and Asp-376 mutations in the ALS gene are associated with resistance to ALS-inhibiting herbicides in B. japonicus [ 3 , 4 , 5 , 6 ]. In China, control failures of B. japonicus have recently been observed in wheat fields where ALS-inhibiting herbicides are constantly used.…”

The Pro-197-Thr mutation in the ALS gene confers novel resistance patterns to ALS-inhibiting herbicides in Bromus japonicus in China

“…However, B. japonicus has extremely extended to 62.3 million hm 2 in Shijiazhuang, with the highest distribution density > 1000 plants/m 2 after 2009 ( Jiang, 2010 ), leading to wheat yield reduction > 90% ( Wei et al., 2010 ). In 2022, flucarbazone-sodium-resistant B. japonicus populations were reported in Tianjin and Hebei ( Lan et al., 2022 ; Li et al., 2022 ).…”