Estimating nuclear DNA content within 50 species of the genus Phalaenopsis Blume (Orchidaceae)

• Estimating DNA content of Phalaenopsis by using flow cytometry was established.
• The 2C values of these species ranged from 2.77 pg to 17.47 pg.
• Intraspecific variations in 2C values at aneuploid or euploid levels were observed.
• Various degrees of homogeneity of genome size within taxa give further insight.
• The database of 2C values provided in this research is helpful to orchid breeders.

Estimation of the genome size of Phalaenopsis species is important because this orchid is employed in various research areas including variety improvement and studies of molecular genetics. In this research, the ovary tissue of the orchid flower before pollination was used to estimate the nuclear DNA content (2C value) by flow cytometry for 50 species of four subgenera with eight sections of the genus Phalaenopsis (2n = 2x = 38). Measurements were taken by repeated sampling of the fresh flowers collected from several germplasm banks in Taiwan. The 2C values of 50 species ranged from 2.77 pg in P. philippinensis to 17.47 pg in P. lobbii and varied at different degrees within each subgenus/section. The nuclear DNA contents of species in sections Phalaenopsis and Fuscatae were homogenous without significant difference while those in sections Zebrinae and Amboinenses were highly variable. Subgenera Parishianae and Aphyllae and two sections (Esmeralda and Deliciosae) of subgenus Phalaenopsis showed higher mean 2C values than those of other sections. Intraspecific variations in 2C values were observed in some species. The information provided by the present research on genome size of Phalaenopsis species together with their geographic distribution and studies on molecular phylogeny would give further insight to plant systematics of this genus. At the same time, it would be helpful to orchid breeders to increase the efficiency of their improvement programs.