Simultaneous selection of rubber yield and girth growth in young rubber trees

The importance of the rubber yield from the rubber tree (Hevea brasiliensis) is already well known. Recently, the importance of girth growth and consequently wood rubber tree has been emphasized. Genotypes with greater girth growth produce greater volume of wood. Rubber tree timber can be used as raw material for a vast range of products, substituting wood from natural forests. Rubber tree genotypes that combine high yield and vigorous growth are of great interest for genetic improvement. Thus, the objective of the present study is the simultaneous selection in young rubber tree progenies for dual-purpose rubber yield and girth growth. Twenty-two progenies were used which were assessed at the field in two locations in a randomized experimental block design with three replicates and 3m×3m spacing. The classic selection index was used; this index is a tool that allows all the characters of interest to be used simultaneously. The progeny effect was significant for both variables and in both locations, indicating progeny genetic variability and the possibility of selection. The progeny mean heritability (hˆx¯2) was greater than the heritability based on single individual's level (hˆi2) and within plot heritability (hˆw2). The multicollinearity among the variables was low, so the variables could be used simultaneously to construct the selection index. Four progenies were selected with an 18% selection intensity, but the progenies were different in the two locations. The classic selection index was efficient in simultaneous selection of rubber yield and girth growth in progeny of young rubber trees. Simultaneous selection for rubber yield and vigor is important at the initial stages of genetic breeding and should be done per location. This selection contributes to identifying superior progeny for rubber yield and with potential for double purpose: wood and rubber production.