A unique morphotype of grapevine somatic embryos exhibits accelerated germination and early plant development

A unique morphotype of normally dicotyledonous somatic embryos was observed among in vitro cultures of grapevine (Vitis vinifera L.) Chardonnay. This unique morphotype occurred commonly in a predictable frequency and was easily distinguished by its characteristic, enlarged hypocotyl and distinctive single cotyledon. Histological and scanning electron microscope observations confirmed the complete absence of one cotyledon with concomitant presence of a significantly larger shoot apical meristem. Germination studies showed that this unique morphotype produced shoots earlier; however, overall plant regeneration and establishment in vivo did not differ from those of normal somatic embryos. To date, there have been no distinct, phenotypic differences among the regenerated plants. We hypothesize that the larger shoot apical meristem region was responsible for early shoot development. Other than the loss of one cotyledon during embryo development, this off-type functions as a 'normal' somatic embryo.