CHARACTERIZATION OF WILD OAT (AVENA-FATUA L) POPULATIONS AND AN INBRED LINE WITH MULTIPLE HERBICIDE RESISTANCE

Repeated use of the pre-emergence herbicide triallate has selected for wild oat populations that are resistant (R)(3) to field use rates. Fi eld collections and an inbred R line were shown in greenhouse and petr i dish dose response experiments to be 6- to 20-fold more tolerant to triallate than susceptible (S)(3) lines, R populations and the inbred line were also resistant (8-fold) to the related thiocarbamate herbici de diallate, as well as to the chemically unrelated postemergence herb icide difenzoquat (60-fold), C-14-triallate uptake and translocation p atterns were similar between R and S lines for the first 24 h after ap plication. However, translocation of radioactivity was more rapid in S lines than R lines from 24 through 60 h after application. C-14-difen zoquat uptake was the same in R and S lines 12 h after application, bu t was 10 to 20% higher in R lines than S lines by 24 through 96 h afte r application. Similarly, translocation of radioactivity after C-14-di fenzoquat application was 7 to 14% greater in R than S lines after 12 h, although translocated radioactivity amounts were not significantly different between R and S lines. The relatively minor differences in t riallate and difenzoquat uptake and translocation patterns between R a nd S lines are most likely not of sufficient magnitude to explain the observed resistance levels.