Characteristics of the tetraploid plant derived as a somaclonal variation in lilium longiflorum

Abstract

Somaclonal variation that possibly occurs during the process of plant tissue culture is considered to provide a source of new germplasm. Polyploidy is one of the most frequent incidents among the somaclonal variations. In the present study, we performed cytological and morphological characterization of tetraploid plants that were obtained from long-term subcultured callus culture of Lilium longiflorum. Friable green calli of L. longiflorum were induced from in vitro leaves on solidified MS medium supplemented with 30 g L-1 sucrose and 1 mg L-1 picloram and maintained for 3 years by subculturing routinely on the same medium at 30-day intervals. High regeneration ability was observed after transferring the calli to half-strength MS medium without plant growth regulator, and approximately 6.7% of the regenerated plantlets tested were tetraploid (2n=4x=48). Karyotypic analysis of the control plant (a bulblet-derived plant) showed diploid chromosome number (2n=2x=24) with 4-large submetacentric, 12-medium acrocentric, 4-medium telocentric, 2-small acrocentric and 2-small telocentric chromosomes (L4sm+ M12a+ M4t+ S2a + S2t). Whereas karyotypic pattern of a tetraploid (code no. V18) revealed the completely duplicated set of chromosomes with 8-large submetacentric, 24-medium acrocentric, 8-medium telocentric, 4-small acrocentric and 4-small telocentric chromosomes (L8sm+ M24a+ M8 t + S4a+ S4t). The average number of stomata in leaves of somaclonal tetraploids was less than in control plants, but thicker leaves with greenish color and the alteration of the shape of guard cells were detected in these tetraploids.