Genetic variability and predicted genetic gains for yield and laticifer system traits of rubber tree families

The present study aimed to estimate genetic parameters in order to assess heritability, predict genetic gains, and establish genetic and phenotypic correlations among yield-related traits of 22 families of Hevea brasiliensis (Willd. ex. Adr. de Juss.) Muell-Arg, selected phenotypically for yield. Three early measurements were carried out for the traits dry rubber yield (DRY), annual girth growth (GGR), number of vassel latex rings (NVR) and bark thickness (BKT). Statistical analyses were carried out using the REML/BLUP (restricted maximum likelihood/best linear unbiased prediction) method. The additive genetic variance showed higher values than the residual variance, indicating high genetic variability in the studied population. The high values of heritability obtained indicated that the studied traits are little influenced by the environment and high gains can be obtained by selection in this population. High genetic correlation was found between GGR and BKT in the three years of evaluations suggesting that selection of families on one of these traits would lead to gains for the other trait as well. The magnitude of genetic correlation indicated greater contribution from genetic factors than environmental factors in these correlations. Gains among and within families, by selecting in the first year of assessment for rubber yield, did not vary significantly in relation to the other two years. Thus, selection could be made in the first year of assessment, thereby reducing the cost and time for the selection work with subsequent cloning.