Quantitative genetic parameters for growth and wood properties in Eucalyptus “urograndis” hybrid using near-infrared phenotyping and genome-wide SNP-based relationships

Abstract

A thorough understanding of the heritability, genetic correlations and additive and non-additive variance components of tree growth and wood properties is a requisite for effective tree breeding. This knowledge is essential to maximize genetic gain, that is, the amount of increase in trait performance achieved annually through directional selection. Understanding the genetic attributes of traits targeted by breeding is also important to sustain decade-long genetic progress, that is, the progress made by increasing the average genetic value of the offspring as compared to that of the parental generation. In this study, we report quantitative genetic parameters for fifteen growth, wood chemical and physical traits for the world-famous Eucalyptus urograndis hybrid ( E . grandis × E . urophylla ). These traits directly impact the optimal use of wood for cellulose pulp, paper, and energy production. A population of 1,000 trees sampled in a progeny trial was phenotyped directly or following the development and use of near-infrared spectroscopy calibration models. Trees were genotyped with 33,398 SNPs and 24,001 DArT-seq genome-wide markers and genomic realized relationship matrices (GRM) were used for parameter estimation with an individual-tree additive-dominant mixed model. Wood chemical properties and wood density showed stronger genetic control than growth, cellulose and fiber traits. Additive effects are the main drivers of genetic variation for all traits, but dominance plays an equally or more important role for growth, singularly in this hybrid. GRM´s with >10,000 markers provided stable relationships estimates and more accurate parameters than pedigrees by capturing the full genetic relationships among individuals and disentangling the non-additive from the additive genetic component. Low correlations between growth and wood properties indicate that simultaneous selection for wood traits can be applied with minor effects on genetic gain for growth. Conversely, moderate to strong correlations between wood density and chemical traits exist, likely due to their interdependency on cell wall structure such that responses to selection will be connected for these traits. Our results illustrate the advantage of using genome-wide marker data to inform tree breeding in general and have important consequences for operational breeding of eucalypt urograndis hybrids.

Wood and Pulping Properties Variation of Acacia crassicarpa A.Cunn. ex Benth. and Sampling Strategies for Accurate Phenotyping

“…Comparing AC with eucalypts, comparable values in lignin and cellulose contents were found for urograndis hybrids at similar age [38,40], and kraft pulp yield in the same ranges was reported for E. globulus [14,[38][39][40] at ages ranging from 10-16 years and higher wood density. Regarding the S/G ratio, the low mean with a narrow range (1.5-1.8) found for AC in our study is somewhat different from typical S/G ranges reported for eucalyptus species and hybrids [40][41][42].…”

“…The phenotypic correlations among wood quality traits found in this study are, in general, similar to results reported for other woody species [38,39,42,47]. Kraft pulp yield was correlated with alpha cellulose, glucose, and galactose, and negatively correlated with insoluble lignin.…”

“…Basic density was positively correlated with pulp yield, alpha cellulose, arabinose, galactose, rhamnose, and mannose, showing its interdependency with cellulose contents in the xylem cell wall. This significant, positive basic density correlation with pulp yield is not typically seen in eucalypts, with no correlation or lower values reported [38,39,42].…”

“…For other relevant species of the Acacia genus, a collection of studies dealing with different wood properties supports an ample understanding of the phenotypic variation found in the genus, as shown for A. mangium [23][24][25][26][27], A. auriculiformis [28,29], and their interspecific hybrid [30][31][32][33][34][35][36]. Moreover, there is abundant literature dealing with wood quality traits for other important tree species commercially planted worldwide, contextualizing wood quality traits variation in a wider range of tree species, as shown for eucalypts [37][38][39][40][41][42][43], pines [44][45][46][47][48], and poplars [49][50][51]. Generally, wood quality traits show intermediate to strong genetic control, with greater genetic stability across environments than growth traits, with the tree's phenotype providing a reliable indicator of its genetic merit, making wood quality traits amenable to genetic advancement through selection [52,53].…”

Genotype-by-environment interaction in coast redwood outside natural distribution - search for environmental cues

“…In this study, diameter at breast height (DBH) was the only attribute representing tree growth. Studies across other forest tree species found strong/moderate correlations between DBH and tree height or volume [36][37][38][39] which provides evidence of using DBH as an ideal proxy phenotype for other essential attributes. However, there is decent genetic variability found in DBH -tree height relationship due to differences in individual's response to environment and competition [40].…”