Minimizing inter-genotypic competition effects to predict genetic values and selection in forestry genetic tests

Abstract

The effect of competition is an important source of variation in breeding experiments. This study aimed to compare the selection of plants of open-pollinated families of Eucalyptus with and without the use of competition covariables. Genetic values were determined for each family and tree and for the traits height, diameter at breast height and timber volume in a randomized block design, resulting in the variance components, genetic parameters, selection gains, effective size and selection coincidence, with and without the use of covariables. Intergenotypic competition is an important factor of environmental variation. The use of competition covariables generally reduces the estimates of variance components and influences genetic gains in the studied traits. Intergenotypic competition biases the selection of open-pollinated eucalypt progenies, and can result in an erroneous choice of superior genotypes; the inclusion of covariables in the model reduces this influence.

Genetic control of silvicultural traits in Balfourodendron riedelianum (ENGL.) ENGL.

“…By assuming that the progenies originated from random mating and relatedness within progeny was half-sibs (HS), both coefficients of individual narrow sense ( 2 i h ) and within progeny ( 2 w h ) heritability were overestimated (9.4 and 12.6 %, respectively), in relation to estimates based on the coancestry coefficient ( = 0.138), which were calculated from mating system analysis and using microsatellite markers. Progenies are mainly composed of half-sibs (89-93 %), but some self-sibs, self-half-sibs, and full-sibs also occur (Aguiar 2018). As open-pollinated progenies are always composed of mixtures of different levels of relatedness (Degen and Sebbenn, 2014), it is important to consider the mating system in genetic parameter estimates in studies on the genetic control of traits (Tambarussi et al, 2018).…”

“…The mean heritability among progeny ( h was moderate for DBH at 32 years of age. In provenance and progeny tests, the mortality results in inter-tree competition, affecting the growth of traits as DBH (Magnuseen and Yeatman, 1987;Leonardecz-Neto et al, 2003;Pavan et al, 2011) and decreasing the estimates of genetic parameters as heritability (Leonardecz-Neto et al, 2003;Pavan et al, 2011). As the DBH is a sensitive trait for competition (Magnuseen and Yeatman, 1987;Leonardecz-Neto et al, 2003;Pavan et al, 2011), the individual variation for competition resulted from mortality (16.8 %) can explain the estimated low heritability values.…”

“…In provenance and progeny tests, the mortality results in inter-tree competition, affecting the growth of traits as DBH (Magnuseen and Yeatman, 1987;Leonardecz-Neto et al, 2003;Pavan et al, 2011) and decreasing the estimates of genetic parameters as heritability (Leonardecz-Neto et al, 2003;Pavan et al, 2011). As the DBH is a sensitive trait for competition (Magnuseen and Yeatman, 1987;Leonardecz-Neto et al, 2003;Pavan et al, 2011), the individual variation for competition resulted from mortality (16.8 %) can explain the estimated low heritability values. Under this condition is hard to be efficient in the genetic selection because DBH will reflect a large environmental effect due to competition, which affects also the selection of genotypes, favoring grow of trees of the best progenies for grow traits (Pavan et al, 2011).…”

“…As the DBH is a sensitive trait for competition (Magnuseen and Yeatman, 1987;Leonardecz-Neto et al, 2003;Pavan et al, 2011), the individual variation for competition resulted from mortality (16.8 %) can explain the estimated low heritability values. Under this condition is hard to be efficient in the genetic selection because DBH will reflect a large environmental effect due to competition, which affects also the selection of genotypes, favoring grow of trees of the best progenies for grow traits (Pavan et al, 2011). The coefficient of environmental variation (CV e ) was generally high for the studied traits (> 20 %).…”

Early selection in open-pollinated Eucalyptus families based on competition covariates

“…These covariates were chosen in accordance with Pavan et al (2012) and tested for selection of Eucalyptus progenies by Pavan et al (2011), considerably improving the selection of trees at the end of the cycle. Before analysis of covariance, the linear regression coefficient was tested, since it was significant in both experiments and families x covariate interaction was nonsignificant, showing that it is possible to use these covariates for analysis.…”