Polymorphism in the resistance of Plantago lagopus to herbicides

Seeds from populations of Plantago lagopus were collected from six sites in Israel with different histories of previous herbicide use. Tlamim (T) and Bilu (B) had been previously treated with simazine and bromacil; Naan (N) w ith sulfometuron and diuron; Dvir (D) with diuron, and Givat Brenner (G) an d Rehovot (F) were populations collected in non-cultivated fields that had no history of previous herbicide use. Based on whole-plant response to post -emergence herbicide sprays, isolated chloroplasts and fluorescence studies with excised leaves, it was evident that the T and B populations were tria zine-resistant. The D population was the most resistant to diuron, G was th e most sensitive, whereas B and N populations were intermediate. The N popu lation was the only one that exhibited resistance to ALS inhibitors both at the whole plant and enzyme level. These data demonstrate the polymorphic n ature of P. lagopus showing that resistance to different herbicides has evo lved according to the selection pressure imposed by repeated herbicide appl ications.