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) with sulfometuron and diuron; Dvir (D) with diuron, and Givat Brenner (G) and 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 triazine-resistant. The D population was the most resistant to diuron, G was the most sensitive, whereas B and N populations were intermediate. The N population was the only one that exhibited resistance to ALS inhibitors both at the whole plant and enzyme level. These data demonstrate the polymorphic nature of P. lagopus showing that resistance to different herbicides has evolved according to the selection pressure imposed by repeated herbicide applications.