Selection and genetic gain in rubber tree (Hevea) populations using a mixed mating system

The components of genetic variation and genetic gain obtained with three se lection methods - individual, combined and multi-effect index selection - w ere compared in rubber tree [Hevea brasiliensis (Willd. ex Adr. de Juss.) M uell. Arg.] progenies. The rubber tree is a cross pollinating species with a mixed reproductive system in which the self pollination rate is 22%. Twen ty-two half sib progenies were planted at experimental stations at Pindoram a, Votuporanga and Jau, in Sao Paulo State, using a randomized and complete block design, with five replications and ten plants per Plot. Dry rubber p roduction was assessed when the plants were three years old. Based on the g eneric variability of the populations, Pindorama was the best environment f or the expression of variability. At the individual level, heritability was seriously affected when random progenies from an open pollinating populati on were considered as half sib progenies. Considerable overestimation of ge netic gains occurred during individual, combined and multi-effect index sel ection when the rubber tree reproductive system was not considered as mixed . Selection based on the multi-effect index maximizes genetic progress and should be used more in rubber tree breeding programs.