Plant Regeneration via Somatic Embryogenesis in Larix principis-rupprechtii Mayr

Abstract

Prince Rupprecht’s larch (Larix principis-rupprechtii Mayr) is a native conifer in North China with great economic and ecological values. Somatic embryogenesis (SE) is a powerful tool for the mass clonal propagation in plants. In this study, we described a high-efficiency SE system via indirect pathways and investigated the effect of genotype, culture conditions and phytohormones on SE. Immature zygotic embryos (IZEs) of L. principis-rupprechtii Mayr were used as explant materials. In the induction stage, embryogenic tissues (ETs) were induced on mLV medium supplemented with 2.0 mg L−1 2,4-dichlorophenoxyacetic acid (2,4-D) and 1.0 mg L−1 6-benzylaminopurine (6-BA). The initiation frequencies showed significant differences (p < 0.05) among 20 genotypes of open-pollinated mother trees with the highest induction frequency reaching 30%. For tissue proliferation, proliferation in liquid medium was more efficient compared with proliferation in semi-solid medium, providing a multiplication rate of 3.12 in an 8-day subculture period. As a necessary exogenous plant growth regulator (PGR) for somatic embryo maturation in conifers, abscisic acid (ABA) was optimized at 16 mg L−1 in this system. Next, an orthogonal test on osmotic pressure factors showed 50 g L−1 sucrose, 7 g L−1 phytagel and 75 g L−1 polyethylene glycol (PEG) was the optimal combination for somatic embryo maturation in L. principis-rupprechtii Mayr. Moreover, the dispersion culture method provided a more efficient somatic embryo maturation, up to 545 per gram of fresh weight (FW). Finally, 2 g L−1 of active charcoal (AC) was found to increase the somatic embryo germination rate to 63.46%. The improved protocol of SE will serve as a foundation for establishing mass propagation and genetic transformation of L. principis-rupprechtii Mayr.

Pinus massoniana somatic embryo maturation, mycorrhization of regenerated plantlets and its resistance to Bursaphelenchus xylophilus

“…Interestingly, somatic embryo plantlets treated with low concentrations of PEG in the maturation medium exhibited better survival rates, whereas those treated with high concentrations of PEG rooted better. This phenomenon had not been reported previously, as earlier studies primarily focused on the impact of PEG on maturity (Jiang et al, 2021).…”

“…However, despite the progress made in P. massoniana SE, several challenges still remain, including low frequency of embryonal mass initiation, low number and poor quality of mature embryos, and low plantlet regeneration rates ( Xia et al., 2021 ). The maturation treatment has been found to affect somatic embryo germination ( Salaj et al., 2019 ), making it important to investigate the effects of different maturation treatments on somatic embryo germination and subsequent plant growth ( Jiang et al., 2021 ). Acclimatization stage is also considered a major obstacles to successful micropropagation of conifers ( Mohammed and Vidaver, 1988 ).…”

H2O2 Significantly Affects Larix kaempferi × Larix olgensis Somatic Embryogenesis

“…The ( Larix kaempferi × Larix olgensis ) hybrid parents show a significant interspecific genetic variation, resulting in a hybrid vigor through combining the excellent traits of both parents, such as rapid growth, stem form, timber quality, as well as cold, disease and rodent resistance [ 4 ]. However, due to differences in interspecific flowering times and long fruiting cycles, the efficiency of breeding trait improvement is unfortunately low, making it difficult to achieve trait improvement targets [ 5 ]. Moreover, the currently most broadly applied method of larch asexual reproduction is through cuttings, limiting the widespread application of this excellent tree species.…”

De Novo Sequencing and Transcriptome Analysis Reveal Genes’ Specific Expression in Chinese Fir (Cunninghamia lanceolata) Callus

“…The development of an efficient in vitro regeneration system such as SE for Chinese fir is not only useful for elite germplasm mass propagation but also represents an essential enabling technology for future genetic transformation efforts. SE is considered to be one of the most promising strategies for bulking up elite conifers' verities (e.g., Picea pungens, Larix principis-rupprechtii, and Pinus koraiensis [3][4][5]. SE is a complex process of embryo development.…”