Optimization of rhizogenesis for in vitro shoot culture of Pinus massoniana Lamb.
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ORIGINAL PAPER
Optimization of rhizogenesis for in vitro shoot culture of Pinus massoniana Lamb. Yin Wang1 · Ruiling Yao1
Received: 15 August 2019 / Accepted: 28 September 2019 © The Author(s) 2019
Abstract The rooting capacity of Pinus massoniana is poor, especially for mature trees, and has prevented the development of clonal forestry for P. massoniana. In this study, we varied explant types, subculture times and exogenous hormones for plantlet regeneration and assessed shoots for rooting rate and root number for P. massoniana. Following five repetitive grafts, new shoots from grafts used as explant sources were rejuvenated as observed from juvenile shoot morphology and anatomy, leading to greatly enhanced plant regeneration in comparison to that of mature materials from 26-year-old P. massoniana trees. The rooting capacity of subcultured shoots increased with successive subcultures, reaching a peak at 20 subcultures with 35–40 days per subculture. However, rooting performance was significantly reduced after 30 subcultures. The addition of naphthaleneacetic acid (NAA) plus indoleacetic acid in the medium improved the root number, but the combination of exogenous NAA with paclobutrazol (PBZ) increased rooting rate and root number. We thus greatly improved the rooting capacity Project funding: The work was supported by the Project of Scientific and Technological Plan from the Department of Science and Technology of Guangxi under Grants 2018GXNSFDA281020, AD17195078, 2017GXNSFAA198037 and AA17204087-1, the Natural Science Foundation of China under Grant 31960311 and 31360178, and the Key Program of Guangxi Forestry Bureau under Grant [2016]13 and GL2019KT06. The online version is available at http://www.springerlink.com Corresponding editor: Tao Xu. * Ruiling Yao [email protected] 1
Guangxi Forestry Research Institute, Nanning 530002, Guangxi, People’s Republic of China
of mature P. massoniana trees by optimizing explant types (rejuvenated), subculture times (20 subcultures, 35–40 days per subculture) and addition of NAA + PBZ to the rooting medium. The conditions can be used for efficient plantlet regeneration of P. massoniana. Keywords Exogenous hormones · Pine trees · Rejuvenation · Rhizogenesis · Subculture cycles
Introduction Pinus massoniana, cultivated for its timber and natural resin (Zhu et al. 2010), has an important role in afforestation in southern China. Currently, plantations have been started mainly from seeds, which leads to low-productivity forest stands, severely limiting the commercialization of this important tree (Wang and Yao 2019). For promoting the development of the P. massoniana industry, clonal forestry is very important, as shown by the rapid growth of Eucalyptus plantations and the forestry economy after commercialized application of selected genotypes (Yang et al. 1995). For achieving the desired properties of trees, however, clones can only be selected when the trees have reached maturity (Basheer-Salimia 2007). For most mature trees, plantlet regeneration is problematic w
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