Determination of resistant biotypes of Amaranthus retroflexus L. on triazines.

Considering the fact that since 1966 in our country the mostly produced have been triazine herbicides on the bases of ametryn, simazine, atrazine and prometryn, we have studied resistance of Amaranthus retroflexus from different sites in regard to the above mentioned herbicides. Seed of weed species for which exist-possibility of resistance have been collected from different localities in Vojvodina, such as Backa Palanka, Backi Maglic and Becej. Studies were performed during 1999 and 2000 by whole plant studies (Thurnwachter, 1998) and by petri dish assays (Clay, Underwood, 1989). Plants were treated by range of atrazine rates (Atrazin S-50) including also susceptible, referent population. Results indicate atrazine resistance of Amaranthus retroflexus at Backa Palanka and Backi Maglic sites, which have been treated by triazine herbicides in many years lasting period.