Analysis of habituated embryogenic lines in Asparagus officinalis L.: growth characteristics, hormone content and ploidy level of calli and regenerated plants

Habituated asparagus embryogenic lines derived from eleven genotypes were m aintained on hormone-free medium and grew actively through secondary embryo genesis. Secondary embryos were of single cell origin and emerged from the transversal division of some epidermal or subepidermal cotyledonary cells o f primary embryos. The intensity of secondary embryogenesis was found to be variable between embryogenic lines. Plants regenerated from three of these lines have been previously demonstrated to carry a mutation whose phenotyp e was the direct appearance of somatic embryos on apices or nodes cultured on hormone-free medium. Habituated lines of embryogenic calli and various t issues of embryogenic mutant and wild type plants were analysed for their h ormonal content in ABA, IAA, iP, Z and their metabolites ABA-GE, iPA, iMP, ZR. No significant difference was found between different embryogenic lines , except the level of iPA, or between cladophyll or apex cultures of mutant and wild type plants. Flow cytometry analyses indicated only 34% of the em bryogenic lines were diploid, most of the others bring tetraploid, but 62% of regenerated plants from these lines were diploid. This indicated the pro cess of maturation and conversion selected diploid embryos ill the embryoge nic lines. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.