The methanolic extracts of Verbascum speciosum Schrad were tested for genotoxic and inhibitor activity against cornZea mays L. seed The methanol extracts of leaf stem and root of Verbascum speciosum were diluted 10, 5, and 3.3% and applied to corn seed. The germination percentage, mitotic index and random amplified polymorphic DNA (RAPD) results were compared to control. The results showed that especially 10% diluted leaf, stem and root extracts had a strong inhibitory activity. Also, different concentration methanolic extract caused a decrease mitotic index and an increase chromosomal aberration, and changed RAPD profiles. The changes occurred in RAPD profiles of Verbascum extract treatment included variation in band intensity, loss of bands and appearance of new bands compared with control. The results suggested that RAPD analysis could be applied as a suitable biomarker assay for the detection of genotoxic effects of plant allelochemicals.