Agronomic performance in tetraploid Lilium leichtlinii : larger flowers and earlier flowering

Polyploidization confers many advantages over diploidy in crop production. Asiatic hybrid lilies contain several polyploid cultivars; however, the characteristics improved by polyploidization have not been sufficiently evaluated. Lilium leichtlinii is among the important parental species used for Asiatic hybrid lily establishment and is also used as an edible lily in Japan. In this study, tetraploid L. leichtlinii plants were induced in vitro in a colchicine-containing medium, and their ploidy levels were confirmed using flow cytometry. Subsequently, the characteristics of the tetraploid plants were evaluated in the field to determine those that were improved by polyploidization. Tetraploid L. leichtlinii plants exhibited significantly earlier flowering, wider leaves, and larger tepals than their diploid counterparts. The effects of tetraploidy on flowering time vary among lily species and hybrid groups because tetraploid L. longiflorum plants present with delayed flowering. Because early flowering and large flowers are desirable characteristics for cut flower production, polyploidization is an effective method for improving Asiatic hybrid lilies. Tetraploid plants showed a higher tolerance to Botrytis disease than diploid plants, which is advantageous for both cut flowers and edible lily production. Bulb fresh weight increased 25% in tetraploid plants compared with diploid plants with p value of 0.052 ( t -test), indicating that tetraploidization tend to increase the yield of lily bulbs. The bulb yield of polyploid lilies has not been evaluated before.