Genetic Variation in Drought-Tolerance Traits and Their Relationships to Growth in Pinus radiata D. Don Under Water Stress.

Ahmed Ismael,Emily Telfer,Jaroslav Klápště,Mireia Gomez-Gallego,Heidi Dungey,Ki-Taurangi Bradford,Jianming Xue,Pierre Bellè,Yongjun Li,Marta Gallart,Dean Francis Meason

doi:10.3389/fpls.2021.766803

Abstract

The selection of drought-tolerant genotypes is globally recognized as an effective strategy to maintain the growth and survival of commercial tree species exposed to future drought periods. New genomic selection tools that reduce the time of progeny trials are required to substitute traditional tree breeding programs. We investigated the genetic variation of water stress tolerance in New Zealand-grown Pinus radiata D. Don using 622 commercially-used genotypes from 63 families. We used quantitative pedigree-based (Genomic Best Linear Unbiased Prediction or ABLUP) and genomic-based (Genomic Best Linear Unbiased Prediction or GBLUP) approaches to examine the heritability estimates associated with water stress tolerance in P. radiata. Tree seedling growth traits, foliar carbon isotope composition (δ13C), and dark-adapted chlorophyll fluorescence (Y) were monitored before, during and after 10 months of water stress. Height growth showed a constant and moderate heritability level, while the heritability estimate for diameter growth and δ13C decreased with water stress. In contrast, chlorophyll fluorescence exhibited low heritability after 5 and 10 months of water stress. The GBLUP approach provided less breeding value accuracy than ABLUP, however, the relative selection efficiency of GBLUP was greater compared with ABLUP selection techniques. Although there was no significant relationship directly between δ13C and Y, the genetic correlations were significant and stronger for GBLUP. The positive genetic correlations between δ13C and tree biomass traits under water stress indicated that intraspecific variation in δ13C was likely driven by differences in the genotype’s photosynthetic capacity. The results show that foliar δ13C can predict P. radiata genotype tolerance to water stress using ABLUP and GBLUP approaches and that such approaches can provide a faster screening and selection of drought-tolerant genotypes for forestry breeding programs.

Highlights

Global climate change scenarios predict that large areas of planted forests will be at risk in the future due to warmer temperatures and changing precipitation patterns and drought (IPCC, 2013)
We investigated the use of genomic selection to study the genetic variation in droughttolerance traits of 622 commercially-used P. radiata genotypes from 63 P. radiata families
We’ve demonstrated large genetic variation of P. radiata drought tolerance assessed by plant growth and needle δ13C

Summary

Introduction

Global climate change scenarios predict that large areas of planted forests will be at risk in the future due to warmer temperatures and changing precipitation patterns and drought (IPCC, 2013). Previous modeling studies have estimated that drought-induced mortality in New Zealand forests could decrease the productivity of P. radiata plantations on average by m3 ha−1 Watt et al (2010) and cause an equivalent of $38 M yr−1 loss in Eastern New Zealand forests alone (Xue et al, 2012). Modeling of future climates showed that a 2◦C rise in global temperatures could reduce P. radiata productivity in New Zealand by at least 10% by 2080, due to low precipitation and pathogen outbreaks (Meason and Mason, 2014). The selection and breeding of drought-tolerant forest tree species is being investigated worldwide (e.g., Pita et al, 2005; Roussel et al, 2009; Gaspar et al, 2013; Marguerit et al, 2014; Chakhchar et al, 2017), the genetic basis of drought tolerance is not well understood

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