JWSS - Journal of Water and Soil Science

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In order to produce Tristeza virus-free plants from Satsuma mandarin (Citrus unshiu) cultivars (Ishikawa, Sugiyama and Myogawa), unfertilized ovules of plants suspected of CTV (Citrus Tristeza virus), from Mazandaran Mahdasht orchard were cultured on 4 media.

 Embryogenesis of nucellus tissue of ovules from Ishikawa and Sugiyama cultivars on MS medium were 31% and 25% and on MT medium from Ishikawa was 40.5%. Unfertilized ovules of Myogawa did not germinate on all media.

Nucellar embryos of Ishikawa and Sugiyama developed on MT+GA3+ME were 83% and 95%, respectively. Embryo differentiation, leaf and plantlet formation were observed on MT+GA3+ADE+ME medium. In the stage of two leaves, the plantlets’ growth under 1500 lux illumination was twice its growth under 800 lux illumination. Budding of in vitro plantlets from both cultivars on susceptible to Tristeza and virus-free seedlings of Key Lime did not show any infection by Tristeza.

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The effect of different media including the growth regulators on somatic embryogenesis from Mexican lime was studied. The average embryo formation after 60 days from unfertilized ovules in different media was evaluated at 0 to 33.75%. The most effective hormone to stimulate embryogenesis was GA₃ at 0.01 and 0.1 mg/l concentrations. Malt extract (ME) at 300 mg/l increased embryo formation, whereas at 1000 mg/l, it inhibited embryogenesis but produced embryogenic callus. Banzyl adenine (BA) at 0.1 and 0.01 mg/l concentrations had significant effects on embryogenesis, while embryo formation was inhibited at high concentrations. Embryo development in different media was also studied. The index of mean root length to mean stem length in the MT³ medium supplemented with 0.1 mg/l of GA₃ was observed to be 1.22±0.22, which was regarded a suitable medium for embryo formation, embryo development and plantlet regeneration.