Resistance mechanisms to fenoxaprop-p-ethyl in a late watergrass (Echinochk phyllopogori) biotype from California

摘要

The mechanism(s) of resistance to fenoxaprop-p-ethyl (FE) in R biotypes of Echinochloa phyllopogon, absorption, translocation and metabolism were studied. There were no differences in absorption rates between biotypes; about 50% of applied 14C-FE wasabsorbed by both biotypes 120 rnurs after treatment (HAT). Biotypes did not differ either in the amounts or rates of FE translocated, 98% of applied 14C-FE remaining in the treated leaf. However, there was a good correlation between the rate of herbicidemetabolism and plant resistance. The R biotype produced 2.5-fold more non-toxic (polar) metabolites from the resulting fenoxaprop-acid (FA) than the S biotype 24 HAT. Moreover, the much higher rate of GSH conjugation in the resistant biotype compared tothat in the susceptible one, indicates that GSH and cysteine conjugation is the major mechanism of resistance of the R biotype against FE toxicity, together with a decrease in the rate of de-esterification of FE.