BROAD SENSE HERITABILITY VALUES AND POSSIBLE GENETIC GAINS IN CLONAL SELECTIONS OF HEVEA

Estimates of heritability of nine biometrical characters were computed using data from a replicated mature clonal trial involving 11 clones of rubber tree [Hevea brasiliensis (Wildd. ex Adr, de Juss.) Muell. Ar g.] grown in Tabapua, State of Sao Paulo, Brazil. The characters were: average yield over four years (MY), girth at opening (GO), girth afte r four years of tapping (GC), girth increment over four years of tappi ng (GI), virgin bark thickness (BT), total number of latex vessel ring s (LV), overall density of latex vessels per ring per five millimeters of bark (DV), average diameter of latex vessels (DL) and average dist ance between consecutive latex vessel rings (AD). Total genetic varian ce (Vg), environmental variance (Ve), estimates of heritability (h(2)) on a single and replicated plot basis, and the expected gain (Gs) fro m selection, assuming the top 27.3% of the population, were computed. Broad sense heritability estimates (h(2)) were obtained for all charac ters and there was considerable genetic variation among clones for MY and GI, as indicated by large values of h(2) obtained for these traits . Heritability estimates for GO, GC and BT were moderately high. The e xpected gain in percent of the mean for MY was 29.3%, whereas estimate s for GI, BT and LV were 30.55%, 13.73% and 11.00%, respectively.