Plasticity in Vegetative Growth over Contrasted Growing Sites of an F1 Olive Tree Progeny during Its Juvenile Phase

RESEARCH ARTICLE Plasticity in Vegetative Growth over Contrasted Growing Sites of an F1 Olive Tree Progeny during Its Juvenile Phase Inès Ben Sadok1,2,3,4, Sebastien Martinez1, Nathalie Moutier1, Gilbert Garcia1, Lorenzo Leon5, Angelina Belaj5, Raúl De La Rosa5, Bouchaib Khadari1, Evelyne Costes1* 1 Institut National de la Recherche Agronomique, UMR Amélioration Génétique et Adaptation des Plantes méditerranéennes et tropicales, Campus Cirad, Montpellier, France, 2 Montpellier SupAgro, UMR Amélioration Génétique et Adaptation des Plantes méditerranéennes et tropicales, Campus Cirad, Montpellier, France, 3 Institut de l'olivier de Sfax, Sfax, Tunisie, 4 Université des sciences de Sfax, Sfax, Tunisie, 5 Instituto de Investigación y Formación Agraria y Pesquera, Centro Alameda del Obispo, Córdoba, Spain * Abstract OPEN ACCESS Citation: Ben Sadok I, Martinez S, Moutier N, Garcia G, Leon L, Belaj A, et al. (2015) Plasticity in Vegetative Growth over Contrasted Growing Sites of an F1 Olive Tree Progeny during Its Juvenile Phase. PLoS ONE 10(6): e0127539. doi:10.1371/journal. pone.0127539 Academic Editor: Mohamed Zain Zulfiqhar Jahufer, AgResearch Ltd., NEW ZEALAND Received: January 19, 2015 Accepted: April 15, 2015 Published: June 10, 2015 Copyright: © 2015 Ben Sadok et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability Statement: All relevant data are within the paper and its Supporting Information files. Funding: This work was partly supported by the Department of Genetics and Plant Breeding of INRA Montpellier and FranceAgriMer SIVAL n° 2010–1919 project ‘RegulOlive’. The work was carried out in the frame of a Collaboration Agreement between IFAPA (Spain) and INRA (France) for cooperation on olive breeding research. Inès Ben Sadok, PhD, was supported by fellowships from Erasmus-Averroes and French University Agency. The funders had no role in Climatic changes impact fruit tree growth and severely limit their production. Investigating the tree ability to cope with environmental variations is thus necessary to adapt breeding and management strategies in order to ensure sustainable production. In this study, we assessed the genetic parameters and genotype by environment interaction (GxE) during the early tree growth. One hundred and twenty olive seedlings derived from the cross ‘Olivière’ x ‘Arbequina’ were examined across two sites with contrasted environments, accounting for ontogenetic trends over three years. Models including the year of growth, branching order, environment, genotype effects, and their interactions were built with variance function and covariance structure of residuals when necessary. After selection of a model, broad sense heritabilities were estimated. Despite strong environmental effect on most traits, no GxE was found. Moreover, the internal structure of traits co-variation was similar in both sites. Ontogenetic growth variation, related to (i) the overall tree form and (ii) the growth and branching habit at growth unit scale, was not altered by the environment. Finally, a moderate to strong genetic control was identified for traits at the whole tree scale and at internode scale. Among all studied traits, the maximal internode length exhibited the highest heritability (H2 = 0.74). Considering the determinant role of this trait in tree architecture and its stability across environments, this study consolidates its relevance for breeding. Introduction Plant architecture is determined by both the genotype and the environment [1]. Considering the particular case of perennial species, plant structure is established by a succession of growth units which characteristics change during ontogeny [2]. Tree architecture is thus determined by genetic, environmental and ontogenetic factors and their interactions. PLOS ONE | DOI:10.1371/journal.pone.0127539 June 10, 2015 1 / 19 Plasticity in Vegetative Growth over Contrasted Sites of Olive Tree study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. The concepts of the architectural analysis [1] have been applied in several forest and fruit species, highlighting the foundation of tree form establishment [3,4,5]. However, accessing the genetic basis of such complex traits requires adapted phenotyping methodology that is manageable in large segregating populations [6]. Based on previous methodological advances [7, 8,9] proposed to decompose tree architectural complexity in a number of elementary variables related to tree constituent’s organization and to the dimension and spatial location of organs (i.e. tree topology and geometry, respectively). Variables associated with either vegetative or reproductive development were measured on different shoot types to account for tree axes polymorphism. This has led to a first screening of architectural traits having potential effect on bearing regularity and fruit quality as well as orchards management efficiency [10,11], and has shown that many of them were genetically controlled [8,9,12]. However, little attention has been paid so far to environmental sources of the phenotypic plasticity even though investigating the inheritance of traits related to the vegetative growth over contrasted environments could permit an early selection of stable architectural traits for fruit tree breeding [13]. The interaction between genotype and environment (GxE) has been largely studied in plant breeding as a mean of producing new cultivars with stable and superior phenotypes [14]. GxE of individual traits have been assessed in numerous experiments with annual crops such as wheat [15], rice [16], oat [17] and soybean [18]; fibres such as cotton [19]; forest trees: poplar [20], pine [21], spruce [22]. Comparatively, fewer studies have been performed on fruit trees, including apple [23, 15], wild cherry [24], and blueberry [25]. The traits studied were mainly related to fruit production and quality, whereas growth traits were poorly represented i.e. limited to stem diameter, height and volume. These latter traits appeared to be significantly impacted by GxE effect in forest trees [26, 27]. In addition to genotype and environment, ontogeny also affects the growth of a tree throughout its life. One of the most evident morphogenetic gradients is the decrease in height increment with tree age, also called age-related decline in growth in forest trees [28]. Genetic characterization of ontogenetic effects can be achieved through functional mapping, as previously performed in poplar [29, 30]. Thus, evaluating the genetic determinism of quantitative architectural traits across environments and over time is challenging for perennial species considering the long juv (...truncated)