Genetic improvement of the rubber tree (Hevea brasiliensis) through conventional breeding approaches depends mainly on the availability of diverse germplasm and the amount of genetic variability present in the population. The present study was undertaken to evaluate the extent of genetic variability in the 1995 Rubber Research Institute of Malaysia (RRIM) Hevea germplasm core collection to determine the correlation and the direct and indirect effects of morphological and bark structural characters on latex yield. The analysis of variance showed highly significant differences among the genotypes for all the nine characters studied. The phenotypic coefficient of variations was higher than the genotypic coefficient of variations for all characters studied, suggesting that the apparent variation is not only genetic but also influenced by the growing environment in the expression of the traits. High heritability and high genetic advance were noted for latex yield, indicating the possibility of improvement for this character through phenotypic selection. Latex yield showed significant and positive correlations with plant girth, total number of latex vessel rings, total bark thickness, and total leaf area at both phenotypic and genotypic level. Path coefficient analysis revealed the highest direct effect of plant girth on latex yield, followed by total number of latex vessel rings and total bark thickness indicating the importance of these characters for yield improvement and their potential as reliable indicators for indirect selection in the established core collection.

通过常规育种方法对橡胶树（巴西橡胶树）的遗传改良主要取决于不同种质的可用性和种群中存在的遗传变异量。本研究旨在评估 1995 年马来西亚橡胶研究所 (RRIM)橡胶树的遗传变异程度。种质核心收集，以确定形态和树皮结构特征对乳胶产量的相关性和直接和间接影响。方差分析表明所研究的所有九个性状的基因型之间存在高度显着差异。所研究的所有性状的表型变异系数均高于基因型变异系数，表明表观变异不仅与遗传有关，而且在性状表达上还受生长环境的影响。乳胶产量的高遗传力和高遗传进步表明通过表型选择改进该特性的可能性。乳胶产量与植物周长、乳胶容器环总数、总树皮厚度、表型和基因型水平的总叶面积。路径系数分析显示植物周长对乳胶产量的直接影响最高，其次是乳胶容器环总数和总树皮厚度，表明这些特征对产量提高的重要性及其作为已建立的核心收集中间接选择的可靠指标的潜力.