Mechanism of resistance to tribenuron-methyl in a resistant biotype of Capsella bursa-pastoris from wheat fields

To ascertain the resistance mechanism of Capsella bursa-pastoris to tribenuron-methyl,the enzyme assays of ALS,GSTs,POD,SOD and CAT in both resistant (R) and susceptible (S) biotypes of C.bursa-pastoris were conducted.The results of in vitro test showed that the sensitivity of ALS to tribenuron-methyl was decreased in the R biotype,the tribenuron-methyl concentration causing 50% inhibition of ALS activity (I50) in R and S biotypes was 0.722 8 and 0.052 1 μmol/L,respectively,and the relative resistance index I50(R)/I50(S) was 13.87.The results of in vivo experiment indicated that ALS activities were inhibited in both R and S biotypes.The ALS activity of the R biotype could be recovered,while that of the S biotype could not; the GSTs activity of R biotype was obviously higher than that of S biotype; the activities of POD,SOD and CAT in R and S biotypes showed no obvious difference.The results suggested that reduced sensitivity of ALS was one of the resistance mechanisms to tribenuron-methyl in C.buusa-pastoris,and the metabolic ability of GSTs might be also related with the resistance.