Acetolactate synthase proline (197) mutations confer tribenuron-methyl resistance in Capsella bursa-pastoris populations from China

The increasing use of AHAS-inhibiting herbicides has resulted in evolved resistance in key dicot weeds infesting cereal cropping systems worldwide. Shepherd’s purse (Capsellabursa-pastoris) is a common dicot weed species in wheat in China with populations that have evolved resistance to the AHAS herbicide tribenuron-methyl. The seeds of eight resistant populations were collected from wheat fields and one susceptible population from road side in Hebei province of China. All eight populations showed high level resistance to tribenuron-methyl with resistance indices of over 100 fold based on whole plant dose response assays in the greenhouse. Comparison of the AHAS gene sequences of the susceptible and resistant populations with Arabidopsis revealed that proline at position 197 of the AHAS gene was substituted by threonine in population CAPBU-HB-2, serine in populations CAPBU-HB-3, CAPBU-HB-4, CAPBU-HB-5, and CAPBU-HB-6, leucine in population CAPBU-HB-7 and CAPBU-HB-8, histidine in population CAPBU-HB-9. The study confirmed tribenuron-methyl resistance in shepherd’s purse in Hebei province of China due to target site mutations at AHAS codon position 197.

The resistance in shepherd’s purse (Capsella bursa-pastoris) to the AHAS herbicide tribenuron-methyl was determined by trials in the field and whole-plant experiments in the greenhouse, and the study confirmed tribenuron-methyl resistance in shepherd’s purse in Hebei province of China due to target site mutations at AHAS codon position 197. The resistant populations were marked in the map. The response and distribution of resistant populations to tribenuron in Hebei province.Figure optionsDownload as PowerPoint slideHighlights
► Shepherd’s purse is the predominant weed in wheat field in China.
► Eight populations showed high level resistance to tribenuron-methyl.
► The resistance in shepherd’s purse was confirmed due to specific point mutations.
► Proline at position 197 of the AHAS gene was substituted in the resistant populations compared with Arabidopsis.