Parâmetros genéticos para caracteres silviculturais em cedro australiano

Abstract

The objectives were to estimate genetic parameters and correlations for silvicultural traits such as diameter and height in Australian red cedar progeny test at different ages; aiming to obtain superior genotypes for wood yield in breeding programs. Sixty six progenies from 12 origins from Australia were used. The experiment was carried out in a randomized complete block design with three replications and 16 plants per plot. The progenies were evaluated for diameter at breast height and height at four ages (31, 54, 74 and 99 months). Genetic parameters and prediction of genotypic values were estimated by the REML / BLUP method using Selegen software. Phenotypic and genotypic correlations for all ages and among characters were also estimated. The likelihood ratio test showed highly significant differences at 1% probability (p <0.01) for diameter at breast height and height at different ages. Estimates of the components of additive genetic variance, individual phenotypic variance and residual variance tended to have higher values at older ages for both traits. The coefficient of determination due to the common environment of the plot ranged from 8.8 to 12% for height and 1.8 to 6% for diameter at breast height. The heritability range for height was smaller and more stable (0.38 to 0.30) over time than diameter at breast height character (0.36 to 0.15). The coefficients of individual genetic variation that quantifies the magnitude of the genetic variation among individuals showed higher estimates than coefficient of genotypic variation between families for both traits analyzed, thus selection within progenies is preferable to that between progenies. Correlations were high and positive for all characters and at different ages, showing selection efficiency from 31 months and indicating that the selection of one character should lead to consistent indirect response in the other. It was also found that the progenies evaluated showed variability, but because of not very expressive values of heritability, progeny selection should be made with caution.