This paper is a study of genetic variation among half-sib progenies of phenotipically selected rubber tree clones [Hevea brasiliensis (Willd. ex. Adr. de Juss) Muell. Arg.] considered as the best in growth and yield performance in a mature clonal population of the Instituto Agronômico in Campinas, State of São Paulo, Brazil. The trial was established in field conditions at the Pindorama Experimental Station, under randomized complete block design with 17 progenies. Growth characters (height, stem diameter and number of whorls of leaves) were studied at 12, 18 and 24 months. Components of variance were estimated from the analysis in an attempt to quantify heritabilities and genetic gains. Data of stem diameters at the age of 12, 18 and 24 months with average of 2.01, 3.16 and 4.68 cm confirm the growth potential of the listed genetic material. The genetic variance among progenies estimated for height, stem diameter and number of whorls of leaves showed good precision. The narrow sense heritabilities at plant level were lower than those obtained for to the mean progeny level. Estimates of the different types of heritabilities were greater for height, followed by stem diameter. These evidences showed favorable to the perspectives for selection response of these characters. Genetic gain estimates for selection among and within progenies showed considerable genetic advances for all characters, revealing the possibility of successful selection within the trial. These results concerning heritabilities, as well as genetic gains, for height and stem diameter indicate that mass selection practiced on these characters is the best alternative for improving this population.
rubber tree; Hevea brasiliensis; heritability; selection; genetic gain; genetic and phenotipic variances