Effect of Plant Growth Regulators on Somatic Embryogenesis and Plantlet Development of Turkey Berry (Solanum torvum SW)

In the present study it was reported on direct somatic embryogenesis and plant regeneration from cotyledon and leaf explants of Turkey berry/pea egg plant (Solanum torvum SW), a medicinally important plant. Somatic embryogenesis has several advantages over other routes of in vitro plant regeneration. Somatic embryogenesis was induced directly from cotyledon and leaf explants on MS medium fortified with BAP (0.5 mg/L)+NAA (0.5-6.0 mg/L). High percentage of somatic embryogenesis (90%), maximum number of somatic embryos formation (62±0.18) along with high percentage (76%) conversion of somatic embryos into bipolar embryos was observed on cotyledon explants in 0.5 mg/L BAP+2.5 mg/L NAA. At the same concentration of BAP (0.5 mg/L)+NAA (2.5 mg/L) also resulted on the maximum percentage of somatic embryogenesis (92%), the highest number of somatic embryos formation (88±0.15) and the highest percentage (76%) of somatic embryos conversion into bipolar embryos in leaf explants. A mixture of globular, heart and torpedo-shaped embryos were germinated on MS medium supplemented with 0.5 mg/L IAA+1.0-4.0 mg/L BAP. Maximum germination frequency (75±0.14) of somatic embryos and plantlet formation was found in 0.5 mg/L IAA+2.0 mg/L BAP, but they didn’t germinate on ½ MSO and MSO media. The survival rate of regenerated plants after field transfer was recorded to be 75%. These regenerated plants were found morphologically similar to donor plants. The present protocol can be used for conservation of the species and also for genetic transformation experiments in S. torvum.

Comparative Study of the Genetic and Biochemical Variability of Polyscias filicifolia (Araliaceae) Regenerants Obtained by Indirect and Direct Somatic Embryogenesis as a Source of Triterpenes

Polyscias filicifolia (Araliaceae) is broadly used in traditional medicine in Southeast Asia due to its antimicrobial, immunomodulating and cytotoxic activities. The main groups of compounds responsible for pharmacological effects are believed to be oleanolic triterpene saponins. However, Polyscias plants demonstrate relatively slow growth in natural conditions, which led to applying a developing sustainable source of plant material via primary (PSE), secondary (DSE) and direct somatic embryogenesis from DSE (TSE). The AFLP and metAFLP genotyping resulted in 1277 markers, amplified by a total of 24 pairs of selective primers. Only 3.13% of the markers were polymorphic. The analysis of variance showed that the PSE and TSE regenerants differed only in terms of root number, while the DSE plantlets differed for all studied morphological characteristics. Further, the chemical analysis revealed that oleanolic acid (439.72 µg/g DW), ursolic acid (111.85 µg/g DW) and hederagenin (19.07 µg/g DW) were determined in TSE regenerants. Our results indicate that direct somatic embryogenesis ensures the production of homogeneous plant material, which can serve as a potential source of triterpene compounds. Plants obtained via somatic embryogenesis could also be reintroduced into the natural environment to protect and preserve its biodiversity.

Comparative transcriptome analysis during developmental stages of direct somatic embryogenesis in Tilia amurensis Rupr

Tilia species are valuable woody species due to their beautiful shape and role as honey trees. Somatic embryogenesis can be an alternative method for mass propagation of T. amurensis. However, the molecular mechanisms of T. amurensis somatic embryogenesis are yet to be known. Here, we conducted comparative transcriptional analysis during somatic embryogenesis of T. amurensis. RNA-Seq identified 1505 differentially expressed genes, including developmental regulatory genes. Auxin related genes such as YUC, AUX/IAA and ARF and signal transduction pathway related genes including LEA and SERK were differentially regulated during somatic embryogenesis. Also, B3 domain family (LEC2, FUS3), VAL and PKL, the regulatory transcription factors, were differentially expressed by somatic embryo developmental stages. Our results could provide plausible pathway of signaling somatic embryogenesis of T. amurensis, and serve an important resource for further studies in direct somatic embryogenesis in woody plants.

High-frequency direct somatic embryogenesis and plantlet regeneration from date palm immature inflorescences using picloram

Background Date palm (Phoenix dactylifera L.) is a traditional crop in arid and semi-arid areas. Its vegetative propagation can be achieved by offshoots, but possible number of offshoots in mother palm trees is limited. Micropropagation is a highly recommended strategy for obtaining date palm elite cultivars using shoot tip and immature inflorescences. In this study, micropropagation procedure using inflorescence explants of Medjool cv. is described. For culture initiation, explants from different spathe lengths were cultivated on Murashige and Skoog medium (MS) supplemented with picloram at 1.0 and 2.0 mg/l combined with 2iP at 0.5 mg/l alone and with both 2iP and BA at 0.25 mg/l for 24 weeks. The obtained direct globular embryos were transferred to maturation media with 0.1 mg/l picloram alone or combined with both 2iP and ABA separately and together for further development. Additionally, multiplication and rooting media were optimized by different cytokinins and auxins for high frequency of plantlet production. Acclimatization of in vitro plantlets was also investigated. Results The highest percentage of globular embryo formation was noticed with explants isolated from spathe lengths ranging from 10 to 15 cm. Addition of BA to initiation media with picloram encouraged a significant effect on embryonic culture formation percentage. Incorporation of ABA and 2iP to maturation medium was an effective factor for individual or multiple embryo emergence. Acclimatization of in vitro plantlets having 3–4 roots was successfully accomplished. Irrigation with the full strength solution (MS) encouraged the highest growth vigor degree, leaf number/plant, leaf width, root number, and root thickness degree of ex vitro plants. Conclusion This research provides an advanced regeneration system for large-scale production of date palm from immature inflorescences of Medjool cv. It opens up the prospects of using picloram with different growth regulators for rapid micropropagation of date palm.