Somatic embryogenesis and plantlet regeneration from nucellar tissue of monoembryonic mango.
Thomas P.
Author Affiliation: Division of Biotechnology, Indian Institute of Horticultural Research, Hessaraghatta Lake, Bangalore-560 089, India.
Journal of Horticultural Science and Biotechnology 74 : 135-139
Abstract : High frequency somatic embryogenesis from nucellar explants was achieved in the monoembryonic mango cv. Arka Anmol. For culture initiation, immature fruits 2-3 cm long about 30-40 days post-pollination were ideal. Culturing half ovules with intact nucellus gave better percentage callusing and more embryonic cultures than using excised nucellus. Among the basal media, Rugini olive (RO) medium followed by Gamborg's B5 (B5) was superior to the Murashige and Skoog (MS) medium for culture establishment and embryo induction. However, B5 medium was better than the others for embryo conversion and further development. Embryonic calluses formed on establishment medium (RO, 6% sucrose, 2 g litre-1 activated charcoal [AC], 2 g litre-1 phytagel, 5 mg litre-1 each of 2,4-D and GA3) on transfer at 2-3 weeks to expression medium (RO with 6% sucrose, 2 g litre-1 AC, 2 g litre-1 phytagel, 400 mg litre-1 glutamine [G1], 1-3 mg litre-1 2,4-D and 10 mg litre-1 GA3) showed pro- and globular embryos in another 2-3 weeks. Further embryo development through heart and early cotyledonary stages occurred in a conversion medium (half strength B5 salts, full RO organics, 4% sucrose, 400 mg litre-1 Gl, 2 g litre-1 phytagel, 2 g litre-1 AC, 100 mg litre-1 casein hydrolysate, 20% [v/v] coconut water, 0.5 mg litre-1 2,4-D and 10 mg litre-1 GA3). Proliferating embryonic cultures could be maintained in this conversion medium giving a continuous supply of embryos. Embryo maturation was obtained in the presence of 1 mg litre-1 abscisic acid. Germination with shoot and root development was obtained in the presence of 0.01-0.1 mg litre-1 thidiazuron. Partly senescent fruits about to drop or having just fallen could also be used as the source of embryonic cultures. Preliminary studies using other monoembryonic cultivars revealed genotype dependent differential responses.