Somatic Embryogenesis of Immature Cunninghamia lanceolata (Lamb.) Hook Zygotic Embryos

Abstract

Two efficient somatic embryogenesis systems were developed in Chinese fir, the most important conifer for industrial wood production in China. Three development stages (cleavage polyembryony, dominant embryo, and precotyledon) of immature embryos derived from 25 genotypes of open-pollinated mother trees were used as initial explants. Cleavage polyembryony-stage embryos with a 12.44% induction rate was the most embryogenic response stage. The highest frequency of embryogenic callus (13.86%) induction was obtained from DCR medium supplemented with 1.5 mg L−1 2,4-dichlorophenoxyacetic acid (2,4-D) and 0.3 mg L−1 kinetin (KN). An average of 53.33 early somatic embryos were produced from approximately 0.2 g (fresh weight) embryogenic callus after 2 weeks of incubation on medium supplemented with 50 μmol L−1 abscisic acid (ABA) and 100 g L−1 polyethylene glycol (PEG) 6000. About 53% dominant embryos have an embryogenic response after a 6-week cultivation on medium supplemented with 1.0–2.0 mg L−1 benzyladenine (BA), 0.2 mg L−1 naphthylacetic acid (NAA) or 2,4-D, and 0.004 mg L−1 thidiazuron (TDZ). After three successive transfer cultures on medium supplemented with 1.5 mg L−1 BA, 0.2 mg L−1 NAA, and 0.004 mg L−1 TDZ, 4.49–16.51% of the embryos developed into somatic embryos.

Desiccation Treatment and Endogenous IAA Levels Are Key Factors Influencing High Frequency Somatic Embryogenesis in Cunninghamia lanceolata (Lamb.) Hook

“…Three method improvements have recently been published for Chinese fir SE. (1) Explants of cotyledon, hypocotyl and mature embryos ( Xi and Shi, 2005 , 2006 ) were used to directly induced somatic embryos, but with a low propagation rate of <10%, which is not suitable for mass propagation; (2) Hu et al (2017) induced embryos indirectly from calluses initiated from immature dominant zygotic embryos by successive culturing on a low auxin/cytokinin concentration medium. This methodology can produce embryos at much higher rate, but somatic embryos may be contaminated with adventitious buds via indirect organogenesis that are not readily distinguished.…”

“…This methodology can produce embryos at much higher rate, but somatic embryos may be contaminated with adventitious buds via indirect organogenesis that are not readily distinguished. (3) Hu et al (2017) also used ABA and PEG to induce somatic embryos starting with embryogenic calluses from immature cleavage polyembryony-staged embryos. Although they obtained mature embryos, these embryos were recalcitrant to obtain normal cotyledon embryos and regenerate plantlets.…”

“…Xi and Shi (2005 , 2006 ) used explants of cotyledon, hypocotyl and mature zygotic embryos for direct SE induction, which is not perspective for mass propagation and further genetic improvements due to low multiplication rates. Hu et al (2017) recently established SE via embryogenic callus using immature zygotic embryos. The system employed ABA and PEG to successfully produce early somatic embryos, but normally developed, late stage somatic embryos were not obtained, and there were no reports about the conversion from somatic embryos to plantlets.…”

Genes, proteins and other networks regulating somatic embryogenesis in plants

“…The process of SE has various phases like initiation, proliferation, maturation, and conversion [ 58 ]. Phase 0 is suggested to have competent single cells giving rise to embryogenic clusters under the influence of PGRs especially auxin [ 33 , 150 ].…”

Establishment of a somatic embryo regeneration system and expression analysis of somatic embryogenesis-related genes in Chinese chestnut (Castanea mollissima Blume)

“…Due to the advantages of high totipotency and genetic stability (Verdeil et al 2007;Ikeuchi et al 2015), somatic embryogenesis is considered as a vital biotechnological tool that can be reliably used for a variety of plants (Sezgin and Dumanoğlu 2014;Hu et al 2017). To date, it has been broadly utilized for early embryo rescue to solve the problem of distant hybridization incompatibility, for shortening the breeding period and speeding up the reproduction process (Giri et al 2004), and for providing a platform for genetically modified breeding (Rugh et al 1998;Vidal et al 2010).…”