Associations among rubber yield and secondary traits in juvenile rubber trees progeny

The reduction in the selection cycle for new rubber tree clones (Hevea brasiliensis) and the increase of rubber yield are sought continuously for crop breeding programs. Thus, the relation of rubber yield was assessed by morphological traits of the plant and structural laticiferous system of rubber trees in open pollinated progeny for indirect selection effect. The progeny was obtained from seeds of 22 selected clones according to yield and vigor of a population base established at the Agronomic Institute in Campinas. Progeny trials were installed in Jau, Pindorama and Votuporanga, in a randomized block design, five replications and ten plants per plot, spaced 2.0 × 2.0 m. The traits assessed at three years after planted were: rubber yield; girth; bark thickness; number of latex vessel rings; average distance between consecutive latex vessel rings; petiole length, petiole diameter and petiole index; leaflet length, leaflet width, leaf width, leaf area and leaf index and leaf storey. Coefficients were estimated by genotypic and phenotypic correlations between these traits. Overall the genotypic correlation coefficients had higher magnitudes compared to the phenotypic, indicating that genetic factors presented more influence on the association among traits. Rubber yield was correlated with traits related to vigor and laticiferous system, but did not correlate with morphological traits. The vigor and system laticiferous traits can be used for indirect selection in rubber tree breeding programs and possibility the shortening the breeding cycle. Girth showed highly significant correlation with bark thickness and leaf storey in Jau, Pindorama and Votuporanga, indicating that these traits can contribute to the secondary traits selection. Future studies with these progeny into adulthood will be important to verify whether the correlations persist, proving indirect selection at the age of three years old as effective.