The growth regulators used for bud regeneration and shoot rooting affect the competence for flowering and seed set in regenerated plants of protein peas

The production of whole plants from explants of protein pea (Pisum sativum L.) using an efficient, reliable and rapid strategy, while maintaining true ness to type, will be required before regeneration can be exploited for gen etic transformation, Seeds of the pea genotypes Terese, Solara, Frisson and P64 (a hypernodulating mutant line of Frisson) were surface-sterilized and imbibed overnight, whereafter embryo axes were dissected and germinated on hormone-free medium for 7-10 d. Hypocotyl sections lacking pre-existing me ristems were harvested and cultured on a range of media with various concen trations and combinations of growth regulators in order to induce either ca ulogenesis or somatic embryogenesis. Differences in responsiveness were app arent between genotypes, but regeneration via caulogenesis was consistently more reliable than via the induction of somatic embryos. Few explants unde rwent somatic embryo production and their conversion into plants has remain ed elusive so far, irrespective of the genotype studied. Conversely, large numbers of buds were produced within 10 d by organogenesis, and healthy, ro otable shoots were obtained. A clear relationship was observed between the growth regulators employed for bud regeneration and shoot routing phases an d the subsequent competence of the regenerated plants for flowering, pod fo rmation and viable seed production.