Effects of Low Temperature on Somatic Embryos Growth, Maturation and Planlet Regeneration of Citrus Mandarin Var Batu 55 (Citrus Reticulata Blanco.)

This study was aimed to determine the effect of incubation at 4°C temperature during multiplication stage of somatic embryos on growth, maturation and plantlets regeneration of citrus Mandarin var Batu 55. Globular somatic embryos were cultured on MT (Murashige & Tucker) medium and incubated at 4°C temperature for 0, 2, 4, 6, 8 weeks. Maturation of somatic embryos was induced by transfering globular somatic embryos on maturation medium (MT + 50 mgl-1 malt extract + 73 mM sorbitol + 73 mM galactose). Cotyledonary embryo was regenerated on MT medium + 50 mgl-1 malt extract + 30 gL-1 sucrose + 2 ppm GA3. The research showed that maturation of somatic embyos at 4°C temperature inhibited growth and maturation of somatic embyos. Fresh weight of somatic embryo incubated at 4°C for 2 weeks lower than fresh weight of embryo cultured without incubation at 4°C, and continuous decline in longer incubation period. Maturation percentage of embryos without incubation at 4°C temperature was 15%, but embryos incubated at 4°C temperature were lower than 9%. There was no effect of incubation at 4°C temperature during somatic embryos multiplication stage on plantlet regeneration percentage