Regeneration of Transgenic Ficus lyrata via Indirect Somatic Embryogenesis and Isolation of Variants for Development of New Cultivars

Abstract

Ficus lyrata is a popular ornamental foliage plant with unique violin- or guitar-shaped green leaves. In our previous study, a grapevine gene VvMybA1 was introduced into F. lyrata via Agrobacterium-mediated transformation, which resulted in the availability of purple-leaved plants. Since VvMybA1 is a transcription factor, the regeneration of transgenic purple-leaved plants might potentially produce variants with multicolored leaves. The objective of this study was to establish a method for regenerating purple-leaved F. lyrata and determine if variants with different coloration or variegation could be isolated from regenerated populations. Leaf explants derived from a completely purple-leaved transgenic plant were cultured on Murashige and Skoog (MS) basal medium supplemented with different concentrations of 6-benzyladenine (BA) and α-naphthalene acetic acid (NAA). Callogenesis occurred in leaf explants, and a subculture of callus-borne explants on the same medium resulted in callus proliferation and the occurrence of somatic embryos. Somatic embryos were more effectively induced from callus pieces cultured on MS medium supplemented with 8.88 μM of BA and 0.27 μM of NAA. More than 30 embryos were induced per callus piece, and the embryos matured and converted to plantlets. MS medium supplemented with 4.92 μM of indolyl-3-butanoic acid (IBA) greatly improved root development. Plantlets were transplanted into soilless substrate and grown in a shaded greenhouse for morphological evaluation. Nine variants with different degrees of coloration and variegation were isolated from the regenerated populations. Our results suggest that the regeneration of transgenic plants that harbor a transcription factor, such as VvMybA1, could be an additional way of isolating novel variants for the development of new cultivars of ornamental plants.