Effects of tissue culture conditions and explant characteristics on direct somatic embryogenesis in Oncidium `Gower Ramsey'

Abstract

The effects of tissue culture conditions and explant characteristics on direct somatic embryogenesis were studied on Oncidium `Gower Ramsey'. Embryo formation was significantly affected by explant position. Leaf tip segments had a significantly higher embryogenic response than other segments of leaves. Adaxial-side-up orientation significantly promoted embryogenesis in comparison with abaxial-side-up orientation. There was no significant effect of sucrose in a range of concentrations (10–60 g l⁻¹). Modified 1/2-MS medium (containing 85 mg l⁻¹ KH₂PO₄) supplemented with 170 mg l⁻¹ NaH₂PO₄ significantly promoted direct somatic embryogenesis. Peptone at 0.5 mg l⁻¹ gave significantly higher emrbyogenic response (80%) on leaf tips than control treatment (50%). The best response on direct embryo formation was obtained on the modified 1/2-MS medium supplemented with 10–20 g l⁻¹ sucrose, 170 mg l⁻¹ NaH₂PO₄ and 0.5 g l⁻¹ peptone.