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Abstract :

The pulse of the tree (diurnal cycle of stem radius fluctuations) has been widely studied as a way of analyzing tree responses to the environment, including the phenotypic plasticity of tree‐water relationships in particular. However, the genetic basis of this daily phenotype and its interplay with the environment remain largely unexplored. We characterized the genetic and environmental determinants of this response, by monitoring daily stem radius fluctuation (dSRF) on 210 trees from a Eucalyptus urophylla x E. grandis full‐sib family over two years. The dSRF signal was broken down into hydraulic capacitance, assessed as the daily amplitude of shrinkage (DA), and net growth, estimated as the change in maximum radius between two consecutive days (ΔR). The environmental determinants of these two traits were clearly different: DA was positively correlated with atmospheric variables relating to water demand, while ΔR was associated with soil water content. The heritability for these two traits ranged from low to moderate over time, revealing a time‐ or environment‐dependent complex genetic determinism. We identified 686 and 384 daily quantitative trait loci (QTL) representing 32 and 31 QTL regions for DA and ΔR, respectively. The identification of gene networks underlying the 27 major genomics regions for both traits generated additional hypotheses concerning the biological mechanisms involved in response to water demand and supply. This study highlights that environmentally induced changes in daily stem radius fluctuation are genetically controlled in trees and suggests that these daily responses integrated over time shape the genetic architecture of mature traits.

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L'article Bartholomé et al. 2020 publié dans The Plant Journal associe plusieurs collègues de l'UMR BIOGECO qui ont travaillé dans le cadre du projet FEDER "ABIOGEN" sur les eucalyptus au Congo et le pin maritime en Nouvelle Aquitaine.

Cet article est l'aboutissement du travail de thèse de Jérome Bartholomé sur eucalyptus, aujourd'hui en poste au CIRAD comme généticien sur le riz à l'IRRI aux Philippines.

C'est la première publication rapportant que les micro-fluctuations du tronc de l'arbre sont sous contrôle génétique.