Effects of type of explant and age, plant growth regulators and medium strength on somatic embryogenesis and plant regeneration in Eucalyptus camaldulensis

Abstract

Plant regeneration was achieved through direct and indirect somatic embryogenesis in Eucalyptus camaldulensis. Callus was induced from mature zygotic embryos and from cotyledon explants collected from 10, 15, 25, and 30-day-old seedlings cultured on Murashige and Skoog (MS) basal medium supplemented with different concentrations of naphthaleneacetic acid (NAA). Maximum callus induction from mature zygotic embryos was obtained on MS basal medium containing 1 mg l -1 NAA. The frequency of callus development varied based on the age of the cotyledon explants 10-day-old explants giving highest percentage on MS basal medium supplemented with 1 mg l -1 NAA. Callus obtained from mature zygotic embryos gave highest frequency of somatic embryogenesis on MS basal medium containing 0.5 mg l -1 benzyladenine (BA) and 0.1 mg l -1 NAA. Separate age wise culture of the calli, obtained from cotyledons of different ages cultured separately, revealed high somatic embryogenic potential on callus from 10-day-old cotyledons. Direct somatic embryogenesis too was obtained from hypocotyl explants without an intervening callus phase on MS basal medium containing 0.5 mg l -1 BA. The effects of abscisic acid (ABA), sucrose, and different strengths of MS medium on somatic embryo maturation and germination were also investigated. Number of mature somatic embryos increased with lower concentrations (0-1 mg l -1 ) of ABA while no significant differences were observed at higher concentrations (2-5 mg l -1 ) of ABA. Compared to basal medium containing lower concentrations of sucrose (1%), the MS medium supplemented with higher levels of sucrose (4%) showed significantly lower frequency of mature somatic embryos. Basal medium without any dilution gave the highest number of immature embryos. However, the number of mature embryos was high at higher medium dilutions.

Plant regeneration from axillary bud derived callus in white yam (Dioscorea rotundata)

“…Several factors are critical for the induction of embryogenic calli including type and age of explants, culture medium, concentration and combination of plant growth regulators (Prakash and Gurumurthi 2010). In the present study, the size and age of the axillary bud explants were found to be critical for calli induction in D. rotundata.…”

Tissue Culture of Corymbia and Eucalyptus

“…NAA at concentrations between 10.8 and 81.0 µM has been used for somatic embryogenesis from C. citriodora, E. camaldulensis, E. dunnii, and E. globulus zygotic embryos, cotyledons, or germinating seedlings, sometimes with the addition of 100 mL L −1 coconut water or 0.5-1 g L −1 casein hydrolysate [73][74][75][76]81,[132][133][134]. NAA at 5.4 µM has been used in combination with 2.22 µM BA or 4.52 µM 2,4-D for inducing embryogenic callus from zygotic embryos, hypocotyls, or cotyledons of E. globulus and E. nitens [134,135], with coconut water at 100 mL L −1 incorporated into the callogenesis medium for E. nitens [135].…”

“…NAA at 5.4 µM has been used in combination with 2.22 µM BA or 4.52 µM 2,4-D for inducing embryogenic callus from zygotic embryos, hypocotyls, or cotyledons of E. globulus and E. nitens [134,135], with coconut water at 100 mL L −1 incorporated into the callogenesis medium for E. nitens [135]. Callogenesis has been induced using 100 µM indole-3-butyric acid (IBA) for E. globulus hypocotyls or cotyledons [136], while 2.22 µM BA has been used for callogenesis from E. camaldulensis hypocotyls [133]. Picloram at 20.7-50.0 µM induces somatic embryogenesis from E. grandis cotyledons, E. globulus hypocotyls and cotyledons, and E. globulus and E. saligna × E. maidenii F.Muell.…”

“…Embryogenic calli are typically transferred to standard shoot proliferation media for embryo development, including hormone-free media [81,86] and media containing 4.44-5 µM BA and 0.54-2.70 µM NAA [132,133,135,136]. Somatic embryos can then be germinated on hormone-free MS medium [73][74][75][76]132,134], MS medium with 0.89 µM BA, and 1.08 µM NAA [74], MS medium with 1.24 µM BA, 2.46 µM kinetin, and 2.48 µM NAA [74], or half-strength MS medium with 2.22 µM BA and 0.54 µM NAA [133].…”

“…Somatic embryos can then be germinated on hormone-free MS medium [73][74][75][76]132,134], MS medium with 0.89 µM BA, and 1.08 µM NAA [74], MS medium with 1.24 µM BA, 2.46 µM kinetin, and 2.48 µM NAA [74], or half-strength MS medium with 2.22 µM BA and 0.54 µM NAA [133]. Embryo germination has also been performed on filter paper suspended over liquid MS medium containing 0.44 µM BA [138].…”