Kumar Sonika, El-Hawaz Rabia, Li Zhigang, Lawson John, Parris Stephen, Kangben Foster, Carneal Lauren, Hopkins Jeff, Naylor-Adelberg Jacqueline, Adelberg Jeffrey, Reighard Gregory, Gasic Ksenija, Carr Chalmers, Saski Christopher A
Department of Plant and Environmental Sciences, Clemson University, Clemson, SC 29634, USA.
Titan Farms, Ridge Spring, SC 29129, USA.
Int J Mol Sci. 2025 Sep 6;26(17):8698. doi: 10.3390/ijms26178698.
Fruit tree rootstock breeding is prolonged by extended juvenile phases, high heterozygosity, limited germplasm diversity, and hybrid incompatibilities, often requiring four decades to release new cultivars. Direct somatic embryogenesis (DSE) in established peach rootstocks presents a promising avenue for rapid genetic transformation and breeding. However, peach is highly recalcitrant to in vitro regeneration, posing major challenges for organogenesis and somatic embryogenesis (SE). This study evaluated the effects of 2,4-dichlorophenoxyacetic acid (2,4-D) and Kinetin (KIN) on SE %, SE productivity, and callus % rate in the widely used Guardian peach rootstock. A 5 × 3 full factorial completely randomized design was used to test 15 different combinations of 2,4-D and KIN on immature cotyledons, classified as upper or lower based on their position on the preculture medium. Media formulation containing a higher concentration (3.2 µM) of 2,4-D and KIN induced SE in ~50% of lower and ~85% of upper cotyledons. Optimal SE productivity occurred with higher KIN (3.2 µM) and reduced 2,4-D (2.6 µM). Callus formation peaked with 1.8 µM 2,4-D and 3.2 µM KIN. This highly reproducible research establishes a robust whole plant regeneration system via DSE in Guardian peach rootstock using immature cotyledons, providing a foundation for expedited trait manipulation through biotechnological approaches.
果树砧木育种因幼年期延长、高度杂合性、有限的种质多样性和杂交不亲和性而进展缓慢，通常需要四十年才能推出新的品种。在已有的桃砧木中直接体细胞胚胎发生（DSE）为快速遗传转化和育种提供了一条有前景的途径。然而，桃对离体再生高度顽拗，这给器官发生和体细胞胚胎发生（SE）带来了重大挑战。本研究评估了2,4-二氯苯氧乙酸（2,4-D）和激动素（KIN）对广泛使用的“守护者”桃砧木的体细胞胚胎发生率、体细胞胚胎生产率和愈伤组织发生率的影响。采用5×3全因子完全随机设计，测试2,4-D和KIN的15种不同组合对未成熟子叶的影响，根据其在预培养基上的位置分为上部或下部。含有较高浓度（3.2 µM）的2,4-D和KIN的培养基在约50%的下部子叶和约85%的上部子叶中诱导了体细胞胚胎发生。最佳体细胞胚胎生产率出现在较高的KIN（3.2 µM）和较低的2,4-D（2.6 µM）条件下。愈伤组织形成在2,4-D浓度为1.8 µM和KIN浓度为3.2 µM时达到峰值。这项具有高度可重复性的研究通过使用未成熟子叶在“守护者”桃砧木中建立了通过DSE的强大全植株再生系统，为通过生物技术方法加速性状操作奠定了基础。
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