Abstract The aim of this study was to evaluate Eucalyptus badjensis concerning the genetic variation for growth traits and the potential of the species in supporting a breeding programme. The field trial was a provenance/progeny test established in Campina da Alegria, Santa Catarina, Brazil (latitude 26°52′05.1″ S, longitude 51°48′47.5″ W, altitude 1,015 m) in a soil classified as Latossolic Alumino-Ferric Brown Nitosol. The experiment comprised 60 open-pollinated progenies from the provenances Glenbog and Badja State Forest, New South Wales, Australia. Ten replicates and plots with six plants in row were used. At the age of 17 years, 279 trees were assessed for diameter of the bole at breast height (DBH), total tree height (H) and volume of wood with bark (Vol). After submitting the data to statistical genetic analysis, the overall means for DBH, H and Vol were 45.17 cm, 33.30 m and 2.84 m3, and the estimates of additive coefficient of variation [ C V a(%)] were 12.59%, 5.91% and 26.51%, respectively. Heritability coefficients of additive effects ( h a 2) were also estimated and the following values were found: 0.443, 0.312 and 0.358. Thirty-nine trees from 25 different progenies were selected. The expected means of the provenances after improvement were 50.02 cm, 34.35 m and 3.47 m3 for DBH, H and Vol, respectively.

O objetivo deste trabalho foi avaliar a eficiência de diferentes métodos de seleção quanto aos caracteres ligados ao crescimento do fuste e o potencial da seleção precoce de genitores. Em 48 progênies de meios-irmãos de Pinus taeda L., foi medido o diâmetro do fuste a 30 cm e a 1,30 m do solo, aos 16 e 84 meses de idade, além da altura total. As progênies foram cultivadas em espaçamento tradicional e reduzido. Os componentes de variância, parâmetros e valores genéticos aditivos foram obtidos a partir de um modelo de análise individual. A seleção indireta foi de eficiência similar à direta quanto ao diâmetro (93%) e menor quanto à altura (78%). A seleção seqüencial foi 16% (altura) e 28% (diâmetro) mais eficiente que a seleção única. A eficiência da seleção combinada foi maior em relação a direta para diâmetro. Vinte genitores selecionados por valores genéticos aditivos quanto ao diâmetro, aos 16 e 84 meses, aumentaram a média em 7,6% e 8,1%, respectivamente. A alta magnitude da correlação genética no que diz respeito ao diâmetro entre idades revelou que esse caráter, avaliado aos 16 meses de idade, prediz o crescimento aos 84 meses. Isso reduz custos de avaliação de progênies, antecipa o desbaste de genitores e a oferta de sementes melhoradas.

The objective of this work was to evaluate the efficiency of different methods of selection in growth traits and early selection. Individual total height and stem diameter at 30 cm above the ground in close-spaced early genetic evaluation at 16 months were assessed. In a 84 month sib cohort, as a comparison, height and diameter at breast height were evaluated. Phenotypic and genetic parameters for height and diameter were estimated for 48 open-pollinated families of loblolly pine (Pinus taeda L.) planted in Southern Brazil using an individual tree model. In this retrospective study, the indirect selection was of similar effectiveness as direct selection in stem diameter (93%) and less effective in height (78%). The two-stage successive culling process was 16% (height) and 28% (diameter) more efficient than the direct selection. The combined selection enhanced the accuracy of mature selection and increased expected genetic gain for diameter. Selecting 20 parents with the highest breeding values predicted by BLUP, at 16 and 84 months, attained a genetic gain of 7.6% and 8.1% in stem diameter. The strong age-age genetic correlation indicated that diameter was highly correlated to genetic level which implies that growth at 84 months could be improved by early selection of diameter at 16 months. This will provide quicker genetic gains by offering improved seeds earlier.