Source Year: 2002

Twenty-six progenies resulting from the crosses of 15 clones of Hevea brasiliensis, H. pauciflora and H. benthamaniana were studied in Bahia, Brazil to estimate general combining ability (GCA) and to evaluate the effect of the array of the parents on the estimates of GCA in unbalanced mating design. Additive and non-additive effects were involved in the control of dry rubber production, trunk girth, bark thickness and resistance to South American leaf blight (Microcyclus ulei). The clones Fx 3864, AVROS 1126, AVROS 255 and Fx 2261 showed the highest estimates of GCA for dry rubber production. AVROS 1126 and AVROS 255 also presented high GCA estimates for trunk girth and bark thichness whereas Fx 3864 and Fx 2261 had low estimates for severity of South American leaf blight. The GCA estimates are greatly affected by using either 1 or 3 cycles (10 tapping/cycle) of the modified Hamaker-Morris-Mann test.