Genomic Breeding for Diameter Growth and Tolerance to Leptocybe Gall Wasp and Botryosphaeria/Teratosphaeria Fungal Disease Complex in Eucalyptus grandis.

Makobatjatji M Mphahlele,Gary R Hodge,Fikret Isik,Alexander A Myburg

doi:10.3389/fpls.2021.638969

Makobatjatji M Mphahlele, Gary R Hodge + Show 2 more

Open Access

https://doi.org/10.3389/fpls.2021.638969

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Abstract

Eucalyptus grandis is one of the most important species for hardwood plantation forestry around the world. At present, its commercial deployment is in decline because of pests and pathogens such as Leptocybe invasa gall wasp (Lepto), and often co-occurring fungal stem diseases such as Botryosphaeria dothidea and Teratosphaeria zuluensis (BotryoTera). This study analyzed Lepto, BotryoTera, and stem diameter growth in an E. grandis multi-environmental, genetic trial. The study was established in three subtropical environments. Diameter growth and BotryoTera incidence scores were assessed on 3,334 trees, and Lepto incidence was assessed on 4,463 trees from 95 half-sib families. Using the Eucalyptus EUChip60K SNP chip, a subset of 964 trees from 93 half-sib families were genotyped with 14,347 informative SNP markers. We employed single-step genomic BLUP (ssGBLUP) to estimate genetic parameters in the genetic trial. Diameter and Lepto tolerance showed a positive genetic correlation (0.78), while BotryoTera tolerance had a negative genetic correlation with diameter growth (−0.38). The expected genetic gains for diameter growth and Lepto and BotryoTera tolerance were 12.4, 10, and −3.4%, respectively. We propose a genomic selection breeding strategy for E. grandis that addresses some of the present population structure problems.

Highlights

Fast-growing plantation forests are essential to the pulp, paper, and timber industries and the emerging biorefinery and biomaterials industries (Perlack et al, 2005; Cetinkol et al, 2012; Devappa et al, 2015; Stafford et al, 2020)
The heritability estimates for Leptocybe invasa gall wasp (Lepto) tolerance from the ABLUP and single-step genomic BLUP (ssGBLUP) models were the highest at 0.71 and second highest at 0.38, respectively, in Nyalazi, while the estimates for diameter growth and BotryoTera tolerance at the Nyalazi site were reasonably low, ranging from 0.07 to 0.11 for the ABLUP and ssGBLUP models, respectively (Table 1)
The overall heritability estimates across sites were higher for the ABLUP model with Lepto tolerance moderately high at 0.54, diameter growth at 0.33, and BotryoTera tolerance at 0.23 (Table 2)

Summary

Introduction

Fast-growing plantation forests are essential to the pulp, paper, and timber industries and the emerging biorefinery and biomaterials industries (Perlack et al, 2005; Cetinkol et al, 2012; Devappa et al, 2015; Stafford et al, 2020). Volume growth and wood density are essential measures for forest plantation productivity (Raymond, 2002). Pest and pathogen challenges have increased in severity in the past decades, posing a significant risk to Eucalyptus plantation forestry productivity and sustainability in subtropical regions (Wingfield et al, 2015). How to ensure continued genetic gains for volume growth in the presence of severe pest and pathogen challenges has become an essential question for plantation species such as Eucalyptus grandis

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