Improvement of in vitro gynogenesis induction in onion (Allium cepa L.) using polyamines

The effects of polyamines on gynogenetic embryogenesis and regeneration of plantlets in onion were studied. Whole flowers from two onion genotypes, 'V alcatorce INTA' cultivar and 'Torrentina' population, were used as initial explants. Embryo induction was greatest with a combined treatment of 2 mM p utrescine and 0.1 mM spermidine. Addition of putrescine alone, with a few e xceptions, did not have any significant effect on either embryo induction o r haploid plantlet production for both onion genotypes. 'Torrentina' showed a higher embryo generation capacity (9.5%) than 'Valcatorce INTA' (2.8%). Fast regeneration of embryos was achieved (from 60 to 90 days) as compared to a previously reported time of 46-152 days. The use of spermidine (0.1 mM ) after 15 days of culture promoted further embryo maturation and plantlet formation. 'Torrentina' produced more haploid plants (1.90%). This is the f irst report of successful use of polyamines for induction of gynogenic embr yos and regeneration of onion plantlets. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.