Somatic embryogenesis by liquid culture of epidermal layers in sunflower: from genetic control to cell development

Embryos were obtained using liquid medium culture of sunflower hypocotyl epidermis layers according to the Pelissier et al. (1990) method. In the present work we identified genetic factors controlling somatic embryogenesis and we evidenced the role of ionic channels in embryogenic tissues. Two traits, the number of embryogenic explants (EE) and the number of embryos (EM) were scored in 74 recombinant inbred lines (RILs) from a cross between lines PAC-2 and RHA-266. Analysis of variance indicated the existence of highly significant differences among the parental genotypes and their RILs. Heritability for the somatic embryogenesis traits studied were high (0.64 for EE and 0.77 for EM). Four quantitative trait loci (QTLs) for EE and seven for EM were detected using composite interval mapping. The QTLs for EE explained 48% of the phenotypic variation while the QTLs for EM explained about 89% of the variation, thus revealing several genomic regions related to somatic embryogenesis control in sunflower. In order to study the distribution of ion channels in somatic embryos as compared to zygotic ones, we used a fluorescent-labelled phenylalkylamine, DM-Bodipy PAA, as a probe. Fluorescence labelling was determined by confocal microscopy. The probe intensively labelled the protoderm and epidermis cells in both zygotic and somatic embryos. Callus exhibited labelling on sites where somatic embryos developed. Considering that the location of phenylalkylamine (PAA) binding sites is related to the distribution of ion channels, the high intensity in the protoderm and epidermis of embryos, point to similar properties and functions and their key role in embryo development.