Effects of Auxin Combinations on Somatic Embyogenesis in Cucumis sativus L.

Abstract

Effects of 2, 4-dichlorophenoxyacetic acid (2, 4-D), a -naphthaleneacetic acid (NAA) and indole-3-acetic acid (IAA) either alone or in combinations of the two at various concentrations in callus induction media on somatic embryogenesis from cotyledon explants of Cucumis sativus L. cv. Fushinarimidori were studied. NAA and 2, 4-D were beneficial to somatic embryo formation. IAA induced adventitious shoot production but failed to stimulate somatic embryo formation. The most effective auxin for somatic embryogenesis was 2, 4-D, which induced the highest frequency somatic embryogenesis at the concentrations of 1.0 and 2.0 mg•liter-1. The number of somatic embryos formed was, however, significantly larger with 2.0 mg•liter-1 than at 1.0 mg•liter-1 2, 4-D.A combination of 0.5 mg•liter-1 2, 4-D and 10.0 mg•liter-1 NAA led to a high frequency of somatic embryo formation and as many somatic embryos as 2, 4-D alone at 2.0 mg•liter-1 Furthermore, either 1.0 mg•liter-1 2, 4-D plus 1.0 mg•liter-1 NAA or 2.0 mg•liter-1 2, 4-D plus 0.5 mg•liter-1 NAA resulted in a greater production of somatic embryos as compared with 2.0 mg•liter-1 2, 4-D. In contrast, when 2, 4-D was combined with IAA, only somatic embryos and no adventitious shoots were formed. Somatic embryogenic capacity, however, was significantly restricted by the addition of IAA, and both the frequency of somatic embryo formation and the yield of somatic embryos decreased quadratically with an increasing concentration of IAA.