MINI-CUTTINGS TECHNIQUE FOR VEGETATIVE PROPAGATION OF Dalbergia nigra

ABSTRACT The usual propagation method for Dalbergia nigra is via seedings; however, the seasonal supply has a variable quantity of seeds which limits the continuous production of seedlings. Therefore, the objective of this study was to establish a vegetative propagation protocol via mini-cuttings technique for D. nigra from juvenile shoots obtained from seedlings. The experimental design was completely randomized in a 2 x 2 x 4 factorial scheme, with two geographical origins: two controlled release fertilizer doses (4.0 and 8.0 g.dm-³) and four indole-3-butyric acid (IBA) concentrations (0; 2,000; 4,000; and 6,000 mg.Kg-1), with four replications. The mini-cuttings were removed from the tubes after 60 days of propagation in the greenhouse, and the substrate was completely removed by washing in running water to observe the roots. The survival percentage, rooting, rooting speed and variables related to mini-cuttings vigor (largest root length (RL, cm.plant-1), number of roots (NR), surface area (SA, mm2), root volume (RV, mm³) and root dry mass (RDM, g.plant-1) were measured. The results indicated that D. nigra has an aptitude for vegetative propagation by mini-cuttings with survival values and rooting greater than 70%. Geographical origins present a different set of responses for survival, rooting and vigor of mini-cuttings. Stock plant nutrition influences mini-cuttings root growth. IBA concentrations did not promote an effect on the mini-cuttings rooting percentage; however, exogenous auxin at the dose of 6,000 mg.Kg-1 provided mini-cuttings with greater vigor in their radical system. Nonetheless, further research is suggested to define the feasibility of using this regulator in the vegetative propagation of this species.摘要：巴西黑黄檀（Dalbergia nigra）的常规繁殖方式多采用实生苗繁殖，但种子供应受季节影响，产量波动较大，限制了实生苗的连续规模化生产。为此，本研究旨在利用实生苗获取的幼嫩枝条，建立一套基于微型插穗（mini-cuttings）技术的无性繁殖方案。 本实验采用完全随机设计，设置2×2×4三因素析因试验方案：2个地理起源组、2个缓释肥料（controlled release fertilizer, CRF）施用量梯度（4.0 g·dm⁻³与8.0 g·dm⁻³）以及4个吲哚-3-丁酸（indole-3-butyric acid, IBA）浓度梯度（0、2000、4000、6000 mg·kg⁻¹），每组设置4次生物学重复。 在温室环境中繁殖60天后，从育苗管中取出微型插穗，以流水冲洗完全去除基质以观察根系发育情况。本研究测定的指标包括插穗成活率、生根率、生根速率，以及与插穗活力相关的多项指标：最大根长（RL, cm·plant⁻¹）、根系数量（NR）、根表面积（SA, mm²）、根体积（RV, mm³）与根干质量（RDM, g·plant⁻¹）。 结果表明，巴西黑黄檀具备通过微型插穗开展无性繁殖的潜力，其插穗成活率与生根率均高于70%。不同地理起源的插穗在成活率、生根率及活力指标上呈现出显著的响应差异。母株营养水平会显著影响微型插穗的根系生长。IBA浓度对微型插穗的生根率无显著促进作用，但当外源生长素施用浓度为6000 mg·kg⁻¹时，可显著提升插穗根系系统的整体活力。此外，后续仍需开展相关研究以明确该生长调节剂在该物种无性繁殖中的实际应用可行性。