Abstract
Summary Tree architecture shows large genotypic variability, but how this affects water‐deficit responses is poorly understood. To assess the possibility of reaching ideotypes with adequate combinations of architectural and functional traits in the face of climate change, we combined high‐throughput field phenotyping and genome‐wide association studies (GWAS) on an apple tree (Malus domestica) core‐collection.We used terrestrial light detection and ranging (T‐LiDAR) scanning and airborne multispectral and thermal imagery to monitor tree architecture, canopy shape, light interception, vegetation indices and transpiration on 241 apple cultivars submitted to progressive field soil drying. GWAS was performed with single nucleotide polymorphism (SNP)‐by‐SNP and multi‐SNP methods.Large phenotypic and genetic variability was observed for all traits examined within the collection, especially canopy surface temperature in both well‐watered and water deficit conditions, suggesting control of water loss was largely genotype‐dependent. Robust genomic associations revealed independent genetic control for the architectural and functional traits. Screening associated genomic regions revealed candidate genes involved in relevant pathways for each trait.We show that multiple allelic combinations exist for all studied traits within this collection. This opens promising avenues to jointly optimize tree architecture, light interception and water use in breeding strategies. Genotypes carrying favourable alleles depending on environmental scenarios and production objectives could thus be targeted.
Highlights
Trees have evolved a diversity of architectures enabling their survival, reproduction, and species coexistence under a variety of environmental and ecological conditions (Lines et al, 2012; Fournier et al, 2013)
Plant architecture is key for resources-use efficiencies, as it is at the heart of a fundamental trade-off between carbon gain and water use by impacting leaf area distribution and light interception, water transport and loss, as well as carbon assimilation and allocation
Over the last two decades, many studies identified contrasting behaviours in the plant’s capacity to maintain their water status upon soil drying (often referred to as isohydric or conservative, i.e., that efficiently maintain high leaf water potential, vs anisohydric or optimistic, i.e., that cannot prevent their leaf water potential from dropping as soil drying develops (Klein, 2014)) whose adaptive value depends on the duration and intensity of the water deficit (Sade et al, 2012)
Summary
Trees have evolved a diversity of architectures enabling their survival, reproduction, and species coexistence under a variety of environmental and ecological conditions (Lines et al, 2012; Fournier et al, 2013). In fruit trees, contrasting behaviours in water status maintenance were shown to vary with the season (Franks et al, 2007; Lauri et al, 2016) and crop load (Naor et al, 2008). Stomatal control of transpiration in response to soil water deficit can interact with canopy microclimate variations (temperature, vapour pressure deficit, radiation) (Willaume et al, 2004; Massonnet et al, 2008) which induce acclimation of leaves through modifications of carbon or nitrogen related traits (Ngao et al, 2020). Tree architecture can play a role in leaf water status maintenance through modifications of organ topological connections and xylem water flow (Schultz, 2003; Lauri et al, 2011).
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