Provenance variation of growth rhythm for Dalbergia odorifera seedlings

To investigate the genetic variation in growth rhythm of Dalbergia odorifera seedlings from different provenances, so as to provide a theoretical basis for superior provenance selection and efficient seedling cultivation.

One-year-old seedlings from nine provenances in Hainan were regularly measured for height and ground diameter. The annual growth process was fitted using the Logistic growth curve, and key growth parameters including maximum growth rate (MGR), rapid growth rate (RGR), growth increment during the rapid growth period (RIG), and the proportion of rapid growth period (PRT) were calculated. Correlation and cluster analyses were conducted in combination with geographical and climatic factors. The genetic parameters such as heritability were estimated by the ASReml-R 3.0.

The Logistic model showed a good fit for both height and ground diameter growth (R²>0.98), with seedling growth following a typical “S”-shaped curve, which could be divided into initial, rapid, and late growth phases. Significant differences were observed among provenances in both phenological and growth parameters. The rapid growth period of ground diameter occurred earlier than that of height, with average starting times of day 47 and day 117, respectively. MGR, RGR, and RIG were significantly positively correlated with annual precipitation of the provenances, indicating that moisture is an important environmental factor affecting growth rate. Cluster analysis grouped the nine provenances into two categories based on geographical structure. With the exception of PRT, significant differences in growth rhythm parameters were observed between groups. Genetic analysis revealed that heritability was generally higher for ground diameter than for height, and growth rhythm traits exhibited moderate heritability with low coefficients of genetic variation, indicating that these traits are mainly under genetic control and have high potential for genetic improvement.

The growth rhythm of D. odorifera seedlings exhibits clear differences among provenances and geographic variations. Annual precipitation is an important environmental factor influencing growth rate. The Logistic model can accurately predict growth processes, providing a reliable basis for scientific seedling cultivation, provenance selection and genetic improvement, the results of this study offer important theoretical and technical support for superior breeding and efficient cultivation of D. odorifera.