Leaf morphology, genetic analysis and low temperature requirement for flowering of Verbascum blattaria

Verbascum blattaria L., commonly known as moth mullein, naturalized in the USA that produces white or yellow flowers could be considered as a potential ornamental plant. However, genetic characterization using molecular markers and leaf morphology, colourimetric analysis and flowering of V. blattaria influenced by low temperature treatments was not investigated to evaluate as a potential horticultural and landscape plant use. The basal leaves developed during the rosette-growth stage were oblanceolate with an obtuse leaf apex and incisions at the margin. Leaves produced on the stem during the reproductive development were ovate or lanceolate with an obtuse or acute leaf apex. Regardless of the colour of the petiole and leaf blade during the rosette-growth stage, there were no differences in the sequences of nuclear ribosomal ITS and chloroplast interspacer. All plants produced creamy white flowers with a purplish base corolla. All leaves formed during the vegetative and reproductive development were glabrous. Numerous stalked glandular trichomes were observed in the sepal, pedicel and bracts. Seeds started to germinate in 10 days at 25°C and reached the plateau in 30 days after sowing. The earliest flowering occurred in 131 days when the plants received 20 days of low temperature treatment (CD) (20 CD), producing 76 flowers, the highest number compared to the number of flowers produced by plants that received 0, 40 and 60 CD. Plants that received 20 CD exhibited early flowering, probably because of the early transition from vegetative growth to reproductive development, as judged by the short stem to the first flower.