Modeling the genetic response of diameter growth in poplar hybrids growing in the center of Chile in the presence of Septoria canker

A clonal trial, including 124 hybrid poplars, was planted in the center of Chile in 2014 and Septoria canker was detected in 2016. We propose a new approach to analyzing the relationship between fungi attack and growth. As an example, we report the analysis of the diameter of trees growing in the presence of Septoria canker for three consecutive years. We modeled two linear models. The original ( reduced ) model of the trial and an alternative ( full ) model added the level of attack effect. We compared variances of additive random effects and their interaction with the level of fungi attack, genetic parameters (heritability and environmental variances), and BLUPs of the clonal values. The focus was on modeling the intra-clonal covariation that depends on the interaction between the genetic and micro-environmental effects. Our results show that the most severe fungi attack occurred in trees with the largest growth in diameter. Including the level of attack effect into the full model produced significant changes in the estimation of genetic parameters at age 5. We observed a genotype-by-micro-environment interaction at ages 3 and 4. We conclude that including the level of Septoria attack in the modeling of genetic parameters for diameter growth of poplar hybrids is a way to correct the prediction of the clonal value of each hybrid planted in a trial. Using a full model that included the pathogen effect allowed a better prediction (BLUP) of the clonal worth.