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.
Highlights
Radiata pine (Pinus radiata) is a fast-growing pine species, native to the Central Coast of California and both Guadalupe Island and Cedros Island of Mexico [1]
Dothistroma resistance (DO_R) was calculated as the percentage of needles that were not affected by Dothistroma needle blight, which was equal to 100% minus the percentage of needles that were affected by the disease
Even more negative genetic correlations were observed when the percentage of common clones fell below 10%. These results indicate that the connectivity between trials played a big role in the estimation of genotype by environment (G×E) interactions, and that the estimated low genetic correlations between some trials might be due to low connectivity
Summary
Radiata pine (Pinus radiata) is a fast-growing pine species, native to the Central Coast of California and both Guadalupe Island and Cedros Island of Mexico [1]. Genetics Ltd. Scion and Forest Genetics Ltd provided support for the authors in terms of working hours to conduct the study. Agriculture Victoria provided support for author YL in terms of working hours to conduct the simulation but did not have any additional role in the study design, data collection and analysis, or preparation of the manuscript. Forest Genetics Ltd did not have any additional role in the study design, data collection and analysis, or preparation of the manuscript. Mike Carson and Sue Carson are affiliated to Carson Associates Ltd. Carson Associates Ltd provided support in the form of salaries for authors MS and SC but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. The specific roles of these authors are articulated in the ‘author contributions’ section
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