Interaction between Growth Regulators Controls In Vitro Shoot Multiplication in Paulownia and Selection of NaCl-Tolerant Variants.

Jehan Salem,Deiaa A El-Wakil,Naglaa Loutfy,Ahmed Hassanein

doi:10.3390/plants11040498

Abstract

The interaction between cytokinin, auxin and GA controlled in vitro shoot multiplication in paulownia was influenced by a medium water potential (Ψ) modulation, where it was modulated using different textures or strengths of MS medium, media of different types (MS, WPM, SH and B5) or NaCl incorporation. The interaction between 2 mg/L BAP and 0.1 mg/L NAA expressed the highest shoot number on each media type, but it was better with media of lower water potential (MS and WPM), and MS medium was the best. Ψ of full-strength semisolid MS medium expressed the highest shoot multiplication. The opposite was detected when Ψ of MS medium was changed using half- or double-strength MS. Ψ of full-strength MS medium in semisolid form resulted in a valuable interaction between 2 mg/L BAP, 0.1 mg/L NAA and 0.1 mg/L GA, leading to efficient shoot formation, and it was associated with an increase in internode length and decrease in stem diameter, which facilitated obtaining synseeds with a high ability to convert. High genetic variation was recorded under long-term culture (14 subcultures). Polymorphism using the ISSR technique was higher than that of RAPD. A further increase in polymorphism was detected when NaCl was used, where five salt-tolerant lines were selected. Some salt-tolerant-selected lines showed one or more amplification products of a specific molecular weight that did not appear in the control. For example, with OPA-07 and OPG-02 RAPD primers, all the salt-tolerant-selected lines showed the appearance of amplification fragments (610 bp and 300 bp, respectively) that were not detected in control.

Highlights

Urban and farm areas are expanding all over the world, leading to the loss of natural forest systems resulting in global warming and changes in the rainfall patterns
The maximum shoot formation appeared on MS medium supplemented with 2 mg/L BAP for four weeks where 3.7 shoots/explant were formed
The interaction between 2 mg/L BAP and 0.1 mg/L NAA and Ψ generated by the MS medium in semisolid form was necessary for better shoot multiplication

Summary

Introduction

Urban and farm areas are expanding all over the world, leading to the loss of natural forest systems resulting in global warming and changes in the rainfall patterns. Paulownia belongs to the Scrophulariaceae family with 40 chromosomes (2n = 2x = 40) and provides an ideal solution to this problem It is a fast-growing tree that reaches the harvesting stage in ten years, has good quality timber, requires minimal management and little investment, and tolerates a range of temperate conditions (−10 ◦C–+45 ◦C) [1]. Indole-3-acetic acid (IAA), a-naphthalene acetic acid (NAA), indole-3-butyric acid (IBA) are commonly used auxins to promote root initiation. Cytokinins such as kinetin (6-furfurylaminopurine), BAP (benzylaminopurine), 2iP (2-isopentenyl-adenine and zeatin (4-hydroxy-3-methyl but-2-enylaminopurine) are used to promote cell division and differentiation. Auxins and cytokinins interact synergistically to control cell division and antagonistically to regulate adventitious bud and lateral root formation [6]. Auxin and gibberellin interact to control stem elongation [7]

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Conclusion