Maximization of genetic gain in rubber tree (Hevea) breeding with effective size restriction

The heritability coefficients and the genetic gains associated with individ ual, combined and among and within progeny selection, and with multi-effect index selection in long-term rubber tree [Hevea brasiliensis (Willd. ex Ad r. de Juss.) Muell.-Arg.] breeding were determined using effective populati on size (Ne) restriction. Twenty-two half sib progenies were planted at the Jau Experimental Station, Sao Paulo State, Brazil, in a complete randomize d block design, with five replications and 10 plants per plot. The followin g traits were assessed when the plants were three years old: number of lati ciferous vessel rings (NR), dry rubber production (RP), bark thickness (BT) and stem girth (SG). Significant variability was found among progeny with good chances of obtaining genetic gain for RP, BT and SG. Effective populat ion size restriction caused a greater reduction in genetic gain for RP with combined selection and with the multi-effect index than for individual or among and within progeny selection. The simultaneous use of accuracy values and genetic gain from the lower limits of the confidence intervals for gai n indicated that individual selection is to be preferred in Hevea breeding programs.