Natural Rhizogenesis Boosters for the Vegetative Propagation and Conservation of Dalbergia baronii and Dalbergia normandii Species

Abstract

The Dalbergia genus belongs to the Fabaceae family. Four species of Madagascar’s Dalbergia are called rosewood, including D. baronii Baker, D. louvelii R. Vig., D. maritima R. Vig., D. normandii. Their woods are classified in the first category of natural forest wood in Madagascar. Rosewoods are becoming endangered due to overexploitation and the destruction of their habitat. For this reason, a vegetative propagation technique has been developed through this work in order to optimize the vegetative propagation and to ensure the perpetuation of the two species in their natural habitat. This method consists of macerating Dalbergia cuttings in two biostimulants, of Aloe macroclada gel or Curcuma longa powder, for 30 minutes before planting. To verify the effectiveness of the technique, control cuttings were grown at the same time as the macerated cuttings. The two-way ANOVA results revealed significant effects on treatment, and their interaction for both root and shoot development (p < 0.001). Among the treatments, Curcuma longa powder notably enhanced root and growth development, particularly in D. baronii, while Aloe macroclada gel was most effective in D. normandii. Principal Component Analysis (PCA) supported these findings, with the first principal component (PC1) explaining 91.5% of the total variance, followed by PC2 at 8.5%. The biplot clearly distinguished the treated groups, highlighting the superior performance of Curcuma longa in both root and growth development. This study demonstrated the significant influence of two natural rhizogenesis boosters, Curcuma longa powder and Aloe macroclada gel, on the vegetative propagation of Dalbergia baronii and Dalbergia normandii. Therefore, obtaining a new Dalbergia plant is possible even if we do not have seeds, and subsequently ensuring their conservation. These preliminary results promising for the case of Dalbergia normandii, which is currently endangered.