The emergence of a atrazine resistant black nightshade (Solanum nigrum L.) biotype and molecular basis of the resistance

Seeds from atrazine resistant plants of black nightshade (<I>Solanum nigrum </I>L.)<I> </I>were collected at the railway station Prague-Vršovice, seeds from susceptible plants in Vyšehořovice (Prague East district). Tests on emergence showed that in both resistant and susceptible biotypes it was highest at a seeding depth of 1 mm, and that at the same seeding depth there were statistically significant differences in emergence between the resistant and susceptible biotypes. The resistance or susceptibility to atrazine was tested by both a chlorophyll fluorescence assay and spraying with atrazine. A region of the gene encoding D1 protein of photosystem II was sequenced and compared between the resistant and susceptible biotypes. Resistance to atrazine in the <I>S. nigrum</I> biotype from Vršovice was conferred by a glycine for serine substitution at residue 264 of the D1 protein. In the plants of the biotypes there was excellent correspondence between the presence of the mutation and herbicide resistance. The assay based on restriction analysis of PCR products can be used for rapid detection of the mutation in populations of black nightshade.