Model-assisted analysis of the root traits underlying RSA genotypic diversity in Vitis: a promising approach for rootstock selection?

Abstract

By dissecting the root system architecture (RSA) into its underpinning components (e.g. root emission, axial growth, radial growth, branching, root direction or tropism) and identifying the relationships between them, functional-structural 3D root models are promising tools for analyzing the diversity and complexity of root system phenotypes with Genotype × Environment interactions. The model parameters are assumed to be synthetic traits, less influenced by the environment, and consequently with less polygenic architectures than the integrative RSA traits they drive. Root models can serve as a basis for in silico development of root system ideotypes by highlighting the developmental processes and parameters that most likely influence RSA fitness. Based on this principle, we provide here an overview of our original work on RSA phenotyping and model-assisted trait dissection in grapevine. First, we set up 2D imaging-based phenotyping tools and analysis pipelines for high-resolution quantification of root morphological and architectural characteristics in juvenile grapevines grown in different controlled conditions (hydroponics, rhizotrons and pots). Specific root descriptors (e.g. number of first-order roots, apical diameter, branching density, length of the unbranched apical zone, insertion angle…) were then measured to calibrate the Archisimple 3D RSA model [1] on a set of Vitis rootstock cuttings. We also investigated whether the model parameters were well conserved over time and under different environments. Finally, we characterized the genetic architecture of few parameters among the 138 individus of a mapping progeny derived from an interspecific cross between Vitis vinifera cv. Cabernet-Sauvignon × V. riparia cv. Gloire de Montpellier grown in the field for 2 years. Broad-sense heritability and QTLs analyses were carried out for model parameters and variables outputs with a consensus map, and compared with other QTLs obtained on classical used RSA descriptors. Results give new insights into the genetic control of RSA in grapevine rootstocks.

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