Direct somatic embryogenesis from leaf and petiole explants of Spathiphyllum ‘Supreme’ and analysis of regenerants using flow cytometry

This study established a method of regenerating Spathiphyllum ‘Supreme’ through direct somatic embryogenesis. Somatic embryos occurred in leaf and petiole explants cultured in the dark on a Murashige and Skoog basal medium supplemented with 2.27, 4.54, or 9.08 μM N-phenyl-N′-1,2,3-thiadiazol-5-ylurea (TDZ) in combination with 1.08 μM α-naphthalene acetic acid or 2.26 μM 2,4-dichlorophenoxyacetic acid (2,4-D). Explants with somatic embryos were transferred to fresh medium containing the same concentrations of growth regulators under lighted conditions for embryo conversion. The highest frequencies of leaf explants with somatic embryos and embryo conversion were both 84.4 %, which were induced by 9.08 μM TDZ with 2.26 μM 2,4-D. The frequencies for somatic embryo induction and embryo conversion were both 100 % when petiole explants were induced by 4.54 μM TDZ with 2.26 μM 2,4-D. The number of plantlets produced per leaf explant and petiole explant were as high as 67.4 and 74.4, respectively. Plantlets after transplanting to a soilless substrate grew vigorously in a shaded greenhouse. Liners were stable without phenotypic variation. Flow cytometry analysis of randomly selected plants showed that they all had a single identical peak. The mean nuclear DNA index for ‘Supreme’ was 1.568, and the nuclear DNA content was 14.222 pg 2C−1. The estimated genome size for ‘Supreme’ was 6,954.5 Mbp 1C−1 with a CV at 4.008 %. The results suggest that the regenerated plants have a stable ploidy level and this established regeneration method can be used for highly effective propagation of uniform Spathiphyllum ‘Supreme’.