Nucellar embryogenesis and plantlet regeneration in monoembryonic and polyembryonic mango (Mangifera indica L.) cultivars
Biotic and abiotic stress particularly fungal diseases and salinity are major challenges facing mango cultivations in Oman. Micropropagation technique for multiplying disease resistant and salinity tolerant elite cultivars could be utilized to replace dead and infected plants in mango orchards but standardize in-vitro regeneration protocol via somatic embryogenesis is prerequisite. Nucellar tissues from immature mango fruits of monoembryonic cultivars Alphonso, Amrapali, Dashehari and Zafran, and polyembryonic cultivars Carabao and Turpentine were used as explants to induce somatic embryogenesis plantlets. Gamborg’s B5 macronutrients, Murashige and Skoog micronutrients, iron source, vitamins and organics were used as standard basal media for all types of media used at each stage of somatic embryo development and regeneration. Induction medium 2 containing 2 mg/l 2,4-Dichlorophenoxyacetic acid and 0.5 mg/l 6-Benzylaminopurine were induced highest percentage of primary somatic embryos for Alphonso (22.08%) while induction medium 3 having 1 mg/l 2,4 Dichlorophenoxyacetic acid with sucrose 60 gm/l and induction medium 1 containing 1 mg/l 2,4- Dichlorophenoxyacetic acid and 0.25 mg/l 6-Benzylaminopurine induced highest percentage of primary somatic embryos in Carabao (29.17%) and Turpentine (42.71%) respectively. Maximum somatic embryo germination were achieved in germination medium 2 containing 0.1 mg/l Indole-3-acetic acid and 0.5 mg/l Gibberellic acid for Alphonso (7.34%) and Turpentine (3.34%) while for Carabao (18.59%) in germination medium 1 which does not contain any plant growth regulators. Germinated plantlets are surviving well in ex-vitro conditions after 4 months of transfer to greenhouse and survival rate of 66.66% for Alphonso, 26.68% for Carabao and 49.16% for Turpentine was obtained.
Keywords: Mango, nucellar embryogenesis, monoembryonic, polyembryonic, somatic embryo, germination, survival rate