Indirect somatic embryogenesis and regeneration of Fraxinus mandshurica plants via callus tissue

Yang Liu,Hailong Shen,Cheng Wei,Hao Wang,Xiao Ma,Ling Yang

doi:10.1007/s11676-020-01199-3

Abstract

Somatic embryogenesis of Fraxinus mandshurica has the problems of low somatic embryo (SE) yield, unsynchronized SE development, and a high percentage of deformed SEs. We aimed to improve F. mandshurica SE production by synchronizing SE development, improving SE quality, and inducing root formation to obtain complete regenerated plants. Cotyledons of immature zygotic embryos of F. mandshurica were induced to form callus and then SEs. The SE induction percentage from explants differed among 32 mother trees, and the one with the highest SE induction percentage (29.8%) was used for further experiments. The highest callus induction percentage was 94.2% on ½-strength Murashige and Skoog medium (MS½) supplemented with 0.15 mg·L−1 naphthalene acetic acid. The highest callus proliferation coefficient (240.5) was obtained on McCown’s Woody Plant Medium containing 0.1 mg·L−1 6-benzyl adenine and 0.15 mg·L−1 2, 4-dichlorophenoxyacetic acid. The highest number of SEs (1020.5 g−1 fresh weight) was obtained on MS½ medium supplemented with 1 mg·L−1 6-benzyladenine. The highest number of cotyledon embryos (397/g fresh weight) was obtained by incubating materials on medium containing 1 mg·L−1 abscisic acid and then applying a drying treatment. The cotyledon embryos were milky white, uniformly sized (average length 4.7 mm), and 80% of them were normal. The SE rooting percentage on ½MS medium containing 0.01 mg·L−1 NAA was 37.5%. Overall, the germination percentage of SEs was 26.4%, and complete regenerated plants were obtained after transplanting and acclimation. These results provide more possibilities for the preservation and breeding of F. mandshurica.

Highlights

Somatic embryogenesis is a valuable model for embryo cell biology and molecular biology research (LeluWalter et al 2013; Us-Camas et al 2014), and an effective system for plant germplasm innovation and large-scale propagation of excellent germplasm resources (Park 2014)
After 60-day pre-cultivation, we calculated the frequency of somatic embryo (SE) formed from explants from 32 different F. mandshurica mother trees from two forest farms (Table 1)
SEs formed from explants from 7 out of 15 mother trees growing at the University Forest, Northeast Forestry University, China

Summary

Introduction

Somatic embryogenesis is a valuable model for embryo cell biology and molecular biology research (LeluWalter et al 2013; Us-Camas et al 2014), and an effective system for plant germplasm innovation and large-scale propagation of excellent germplasm resources (Park 2014). As long as there are appropriate explants, culture conditions, and culture environment, most plant species can be induced to form callus and SEs. An indirect somatic embryogenesis system has been established for Castanea mollissima, Carica papaya, and Medicago truncatula, among others (Lu et al 2017; Solórzano-Cascante et al 2018; Orłowska and Kępczyńska 2020). An indirect somatic embryogenesis system has been established for Castanea mollissima, Carica papaya, and Medicago truncatula, among others (Lu et al 2017; Solórzano-Cascante et al 2018; Orłowska and Kępczyńska 2020) For other plants, such as Liriodendron hybrida and Catalpa fargesii, direct and indirect somatic embryogenesis systems produce SEs that can grow into complete plants (Chen et al 2012; Jiang et al 2014)

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Conclusion