Plant Cell, Tissue and Organ Culture 64: 19–25, 2001. © 2001 Kluwer Academic Publishers. Printed in the Netherlands. 19 The effectiveness of nitrogen sources in Feijoa somatic embryogenesis Lirio L. Dal Vesco & Miguel P. Guerra ∗ Departamento de Fitotecnia, CCA, Universidade Federal de Santa Catarina, Cx. Postal 476 – CEP 88034-001, Florian´ opolis, SC, Brazil ( ∗ requests for offprints; E-mail: mpguerra@cca.ufsc.br) Received 18 April 2000; accepted in revised form 11 December 2000 Key words: amino acids, Feijoa, Feijoa sellowiana Berg, nitrogen, somatic embryogenesis Abstract Immature and mature zygotic embryos excised from Feijoa fruits were employed as explants and the effects of NH 4 + and NO 3 − ionic concentration in basal LPm culture medium supplemented with 2,4-D (10 μM) were evaluated. Moreover, the addition of 4 mM of Asn, Gln, and Arg, and levels of Gln (0 to 8 mM) were tested. The original NH 4 + and NO 3 − concentration present in the LPm culture medium supplemented with Gln (4 mM) resulted in the highest somatic embryo number from immature zygotic embryos. For mature zygotic embryos, the addition of Asn, Gln or Arg to the basal LPm culture medium resulted in improved somatic embryogenesis induction. Ten weeks in culture allowed the highest somatic embryo number when mature zygotic embryos were used as explant. Half-strength MS culture medium supplemented with BAP (0.5 μM) enhanced the conversion of somatic embryos to plantlets. Abbreviations: Arg – arginine; Asn – L-asparagine; BAP – 6-benzylaminopurine; 2,4-D – 2,4-dichloro- phenoxyacetic acid; GA 3 – gibberellic acid; Gln – L-glutamine; LPm – von Arnold and Eriksson (1981) modified medium; Kin – kinetin; 1/2 MS – half strength Murashige and Skoog’s; NAA – napthaleneacetic acid; PGRs – plant growth regulators; SE – somatic embryos, somatic embryogenesis; ZE – zygotic embryos Introduction Somatic embryogenesis (SE) recapitulates the mor- phologic and developmental processes that occur in zygotic embryogenesis. An important factor in SE in- duction and development is the nutrient composition of the culture medium. Nitrogen is a major element for in vitro morphogenesis (Halperin, 1995) and dif- ferent nitrogen balances and sources in the culture medium can promote SE induction and development in carrot alfalfa (Lai et al., 1992), rice (Ozawa et al., 1996), white spruce (Barrett et al., 1997), and cotton (González-Benito et al., 1997). Amino acids serve as primary sources of organic nitrogen for the growth of many eucaryotic cells. They additionally promote communication between cells and tissues within multicellular organisms (Young et al., 1999). In Santa Catarina State, in the South of Brazil, Feijoa sellowiana (Mirtaceae) is a native fruit tree at altitudes higher than 1000 m. Although this plant species has been cultivated in commercial orchards in New Zealand, Australia, USA and some European countries, it has only recently been commercially cul- tivated in Brazil. In the natural populations of Santa Catarina, there is great genetic variability (Nodari et al., 1997). Because of the restricted genetic basis of Feijoa in European countries like France, Italy, Spain and Portugal, these countries are interested in obtain- ing new material to broaden the genetic base (Canhoto and Cruz, 1996a). In this species, conventional propagation tech- niques like grafting and cutting are difficult because of the negative effects of phenolic compounds. Micro- propagation techniques based on organogenesis also present serious limitations (Bhojwani et al., 1987; Canhoto and Cruz, 1996a). On the other hand, the induction of SE has shown good results (Canhoto and Cruz, 1996b; Guerra et al., 1997) and is efficient for the large scale propagation of selected genotypes. The