Abstract
The objetive of this work was to evaluate the influence of intergenotypic competition in open-pollinated families of Eucalyptus and its effects on early selection efficiency. Two experiments were carried out, in which the timber volume was evaluated at three ages, in a randomized complete block design. Data from the three years of evaluation (experiment 1, at 2, 4, and 7 years; and experiment 2, at 2, 5, and 7 years) were analyzed using mixed models. The following were estimated: variance components, genetic parameters, selection gains, effective number, early selection efficiency, selection gain per unit time, and coincidence of selection with and without the use of competition covariates. Competition effect was nonsignificant for ages under three years, and adjustment using competition covariates was unnecessary. Early selection for families is effective; families that have a late growth spurt are more vulnerable to competition, which markedly impairs ranking at the end of the cycle. Early selection is efficient according to all adopted criteria, and the age of around three years is the most recommended, given the high efficiency and accuracy rate in the indication of trees and families. The addition of competition covariates at the end of the cycle improves early selection efficiency for almost all studied criteria.
Highlights
In forestry species, the best age to apply genetic selection is at the end of the commercial cycle, when the tree is ready for logging
Since volume is derived from two other traits – height and circumference at breast height, a higher coefficient of variation of 30% is expected in clonal tests with seven‐year‐old Eucalyptus
This response can be explained by the continued growth of trees in the field, where they are affected by several uncontrollable environmental variations
Summary
In forestry species, the best age to apply genetic selection is at the end of the commercial cycle, when the tree is ready for logging At this age, it is possible to make an efficient choice regarding the most productive and best‐adapted genotypes for the planting site. It is possible to make an efficient choice regarding the most productive and best‐adapted genotypes for the planting site This species cycle is long, involving high maintenance and evaluation costs, besides low gains per unit time in comparison with other crops. In this sense, the application of early selection is of great interest, since it maximizes the production. Paludzyszyn Filho et al (2002) evaluated three ways of testing early selection in Pinus taeda and concluded that the sequential method provided the best genetic gain per unit time, but indirect selection was characterized by ease of calculation, with efficiency of 93% in terms of diameter at breast height. Osorio et al (2003), Zas et al (2004), Dean & Stonecypher (2006), Leksono et al (2006), Weng et al (2007), and Beltrame et al (2012) used the same method to analyze the efficiency of early selection in different tree species
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