Abscisic acid induces somatic embryogenesis and enables the capture of high-value genotypes in Douglas fir (Pseudotsuga menziesii [MIRB.] Franco)

Abstract

Douglas fir (Pseudotsuga menziesii) is one of Europe’s most important non-native tree species due to its drought tolerance as well as timber quality and yield. To obtain superior seed from selected parental trees, breeding programs had been established in seed orchards. Douglas fir seed is used as source material for somatic embryogenesis with the aim to select elite genotypes invaluable for clonal mass propagation. To improve given protocols for somatic embryo initiation, we used immature Douglas fir zygotic embryos as explants and abscisic acid (ABA) as plant growth regulator in contrast to the application of auxins and cytokinins. With ABA supplementation, induction frequencies were slightly but in mean higher than with auxin/cytokinin, showing also a strong genotype effect. This offered the possibility to capture SE cultures from otherwise recalcitrant crosses. Furthermore, we observed remarkable differences between the two sets of plant growth regulators concerning the morphological development of the explants, including the absence of non-embryogenic callus by using ABA as inducer. This simplifies the detection of events and the handling of the obtained cultures. Nevertheless, a histological approach suggested, that the same competent cells are addressed by the different hormonal stimulation. Besides, we studied the influence of different points in time of cone harvest, two different basal media and different genetic backgrounds of the explants as well as the maturation ability of the induced embryogenic cultures. In sum, we were able to improve the first steps of somatic embryogenesis and to maintain a significantly higher number of high-value genotypes.

Comparative Transcriptome Analysis of High- and Low- Embryogenic Hevea brasiliensis Genotypes Reveals Involvement of Phytohormones in Somatic Embryogenesis

“…Studies have shown that it is associated with embryo development and maturation [71]. We also observed an increase in relative ABA levels from y to f stages of both genotypes (Fig.…”

Constitutive Overexpression of a Conifer WOX2 Homolog Affects Somatic Embryo Development in Pinus pinaster and Promotes Somatic Embryogenesis and Organogenesis in Arabidopsis Seedlings

“…However, as in most conifer species (see Bonga et al, 2010 ), initiation of somatic embryogenesis in P. pinaster materials older than immature zygotic embryos ( Trontin et al, 2016c ) or cotyledonary or young germinating SEs ( Klimaszewska et al, 2009 ) is still difficult to achieve and may require the additional use of PGRs such as auxin and/or cytokinins. Recently, it was shown that abscisic acid (ABA) supplementation can also lead to initiation of somatic embryogenesis in the Douglas fir ( Pseudotsuga menziesii ) ( Walther et al, 2021 ) and has to be taken into consideration as a signal for SE activation. Induction of secondary somatic embryogenesis from germinated SEs could be obtained but at low rate with a combination of 2,4-D (9.5 μM) and BA (4.5 μM) in P. pinaster ( Klimaszewska et al, 2009 ).…”

Effects of Amino Acids on Callus Proliferation and Somatic Embryogenesis in Litchi chinensis cv. ‘Feizixiao’

“…Each sample was sectioned serially at 8 µm on a microtome (Leica RM2016, Tokyo, Japan). Subsequently, sections were stained with Ehrlich hematoxylin using the method described in a previous report [22]. The prepared slides were observed and photographed using a light microscope (NI/E, Nikon, Tokyo, Japan).…”