Early stage analysis on growth and wood properties of five provenances for Pterocarpus macrocarpus from Thailand.
Objective: Pterocarpus macrocarpus Kurz., commonly known as Myanmar Huali, belongs to the genus Pterocarpus of the Papilionoideae family. The genetic variability and genetic/phenotypic correlations, among the growth and wood traits, were studied for screening of the excellent genetic materials of P. macrocarpus. Screening excellent provenances which are suitable for planting in the western Guangdong Province with fast-growing and high-quality characteristics is great significance for improving economic benefits, reaching the needs of the timber industry, and improving the ecology of the environment. Method: The survival, diameter at breast height (DDBH), tree height (H), single-tree volume (V), under-branch height (Hb), branch angle (θb), moisture content (Cm), wet expansion (Rwe), wood density (ρw), wave velocity (Vtof) and modulus of elasticity (EMOE) were studied in a provenance testing trial on 10-year-old specimens in Baishengyuan, Yangjiang City, in the west Guangdong Province. The variations, genetic parameters, and correlations were estimated for each trait using a mixed linear model. Furthermore, we used exponential equations to select the advantageous provenances and individuals. Result: The survival of 10-year-old P. macrocarpus is high and it grows well. It is suitable for growth in the west of the Guangdong Province. The under-branch height of 10-year-old P. macrocarpus accounted for almost 1/3 of the total tree height. The furniture quality and yield of a single tree were high. The variation coefficients of diameter at breast height (DDBH) and tree height (21.08% and 16.56%, respectively) were relatively small. The variation coefficients of the other three phenotypic traits reached more than 30%, which indicates that the observed traits had a large variation and a good selection. The coefficient of variation of the modulus of elasticity (16.55%) is 2.5 times higher than that of the basic density (6.29%), which indicates that the modulus of elasticity may have more genetic variability than basic density. There were extremely significant differences among the traits. The growth and wood traits were genetically controlled, at a low and medium/strong intensity, at the levels of provenance and individual, respectively. There were significant differences of all traits among the provenances. The growth traits were hereditarily controlled at below a moderate intensity (0.258-0.637) at the provenance level, whilst the wood traits were moderately to intensively controlled (0.321-0.814). The differences in the basic density and wave velocity between provenances of P. macrocarpus is mainly caused by genetic effects. Additionally, the growth traits are more susceptible to environmental impacts. An appropriate growth environment or cultivation and management techniques can obtain certain growth gains. The single tree volume (V) had highly significant genetic correlations with the diameter at breast height (DDBH), tree height (H), under-branch height (Hb) and branch angle (θb). There were insignificant genetic correlations between the wood base density (ρw)/modulus of elasticity (EMOE) and growth traits. Five superior individuals were selected according to the trait weighted index equation, with increases in the DDBH, tree height, volume, base density, wave velocity and modulus of elasticity of 23.319%, 16.503%, 48.025%, 3.569%, 7.033% and 17.767%, respectively. This demonstrates a distinct selection effect. The selected superior individuals were unevenly distributed among the sources, of which P200502 was the most abundant, accounting for 60% of the total selected plants. Conclusion: There were abundant variations in the growth and wood properties among and within the provenances of the 10-year-old P. macrocarpus. The genetic control over the growth and wood properties at the provenance level was above moderate intensity, and good selection effects could be achieved by using the appropriate methods. Superior individuals could be selected for different breeding purposes, to fully benefit from their genetic potentials during the early selection of P. macrocarpus.