Genotype by environment interaction for growth and Dothistroma resistance and clonal connectivity between environments in radiata pine in New Zealand and Australia

Abstract

Twenty-eight clonal trials of radiata pine planted across Australia and New Zealand were used to investigate genetic variation and genotype by environment (G×E) interaction for diameter-at-breast-height (DBH), height and Dothistroma resistance (DO_R). The average narrow-sense heritabilities were 0.11, 0.21 and 0.30 while the average broad-sense heritabilities were 0.27, 0.34 and 0.40 for DBH, height and Dothistroma resistance, respectively. Dothistroma resistance was assessed as the percentage of needles that were not affected by Dothistroma needle blight. G×E interactions were analysed using an approximate reduced factor analytic model. Apparent G×E interactions were estimated for DBH, height and Dothistroma resistance. Estimates of G×E interactions and their standard errors were strongly influenced by the level of connectivity between trials, in terms of common clones and common parents. When there was sufficient connectivity between trials (more than 30% common clones between trials), a high level of G×E interaction was found for DBH and height but not for Dothistroma resistance. In two simulated clonal trials planted in two environments, low connectivity between environments resulted in a lower estimated genetic correlation between environments with an increased standard error. These results suggest that the number of clones in common between clonal trials is a key factor for inclusion in future experimental designs for estimating G×E interaction. When designing clonal trials for use in multiple environments for accurately estimating the level of G×E, if the resource for creating connectivity between environments is limited, at least 30% of the clones need to be in common between environments.

Effect of trait’s expression level on single-step genomic evaluation of resistance to Dothistroma needle blight

“…Similar results were found in a previous study that explored results over several field experiments, with average genetic correlations between different environments ranging from 0.72 to 0.76, depending on the genetic composition of the populations tested, and a slightly lower genetic correlation across different ages of 0.68 [11]. In contrast, Li et al [52] reported genotype by environment interaction (GxE) among environments across New Zealand using a factor analytic approach [53]. However, this statistical approach is confounded with connectivity so that lower genetic correlations may reflect low levels of genetic relatedness (low number of shared parents) among environments.…”

“…However, this statistical approach is confounded with connectivity so that lower genetic correlations may reflect low levels of genetic relatedness (low number of shared parents) among environments. Due to small data set, incompatible with a comprehensive approach, and previous studies of the same needle disease with extensive data, showing low GxE (when genetic connectivity between environments is sufficient) [52], our study did not explore genotype by environment interaction.…”

Quantitative Genetic Variation in Bark Stripping of Pinus radiata

“…The estimated narrow-sense heritability of bark stripping (0.06 to 0.14) was within the lower range of what has been reported for the damage of conifer bark from insect herbivores (0.02-0.40) [12,13,23,[65][66][67]. Similarly, it is in the lower range of the narrow-sense heritabilities reported for resistance to needle pathogens (h 2 = 0.05 to 0.69) in Australian P. radiata plantations [18]. Estimates were also markedly lower than what has been reported for mammalian browsing on the needles of Pseudotsuga menziesii Mirb.…”

“…Genetic gain can, for example, be constrained if the expression of resistance varies according to environmental conditions. Such genotype by environment interaction (G×E) can result in a change in variances or the relative resistance rankings of plant genotypes in different environments [15][16][17][18]. The nature of genetic correlations among traits is also important.…”

“…Tree breeding programs aimed at improving the growth, form, health, and wood traits of P. radiata have been ongoing in Australia and New Zealand since the 1950s [39,40]. The genetic improvement of health has focused on resistance to diseases, especially Dothistroma needle blight and insect pests such as Monterey pine aphid, Essigella californica [18,41,42]. Variation in resistance to insect pests and pathogens has been shown to have a strong additive genetic basis [23,41,43,44].…”