Characterization of triazine-resistant biotypes of common lambsquarters (Chenopodium album), hairy fleabane (Conyza bonaeriensis), and yellow foxtail (Setaria glauca) found in Spain.
Triazine-resistant (R) biotypes of C. album, S. glauca [S. pumila] and C. bonaeriensis were found in Córdoba, S. Spain. The former two R biotypes came from atrazine-treated maize fields, whereas the latter came from simazine-treated non-tilled olive orchards. The R biotypes of C. album and S. pumila and the R biotype of C. bonaeriensis survived exposure up to 5 kg/ha of soil-applied atrazine or simazine, resp. Photosynthetic electron transport in R biotype chloroplasts was unaffected by atrazine and simazine but was inhibited by diuron, as shown by fluorescence induction measurements and in whole leaves. In Hill reaction assays, the R biotype showed high resistance to atrazine and simazine (resistance factors in the range of 350-550), medium to high resistance to ametryn, terbumeton, metribuzin, and monolinuron (resistance factors in the range of 80-250), slight resistance to diuron and methabenzthiazuron (resistance factors in the range 1.1-15.7), and reverse resistance to swep, ioxynil and DNOC (resistance factors <1). It is concluded that the R biotypes have a chloroplast mode of resistance similar to that previously described for other triazine-resistant weed biotypes.