Abstract
Background and AimsThe impact of a fruit tree's architecture on its performance is still under debate, especially with regard to the definition of varietal ideotypes and the selection of architectural traits in breeding programmes. This study aimed at providing proof that a modelling approach can contribute to this debate, by using in silico exploration of different combinations of traits and their consequences on light interception, here considered as one of the key parameters to optimize fruit tree production.MethodsThe variability of organ geometrical traits, previously described in a bi-parental population, was used to simulate 1- to 5-year-old apple trees (Malus × domestica). Branching sequences along trunks observed during the first year of growth of the same hybrid trees were used to initiate the simulations, and hidden semi-Markov chains previously parameterized were used in subsequent years. Tree total leaf area (TLA) and silhouette to total area ratio (STAR) values were estimated, and a sensitivity analysis was performed, based on a metamodelling approach and a generalized additive model (GAM), to analyse the relative impact of organ geometry and lateral shoot types on STAR.Key ResultsA larger increase over years in TLA mean and variance was generated by varying branching along trunks than by varying organ geometry, whereas the inverse was observed for STAR, where mean values stabilized from year 3 to year 5. The internode length and leaf area had the highest impact on STAR, whereas long sylleptic shoots had a more significant effect than proleptic shoots. Although the GAM did not account for interactions, the additive effects of the geometrical factors explained >90% of STAR variation, but much less in the case of branching factors.ConclusionsThis study demonstrates that the proposed modelling approach could contribute to screening architectural traits and their relative impact on tree performance, here viewed through light interception. Even though trait combinations and antagonism will need further investigation, the approach opens up new perspectives for breeding and genetic selection to be assisted by varietal ideotype definition.
Highlights
Since the initial proposition by Donald (1968) to develop ideotypes, ‘i.e. biological models which perform or behave in a predictable manner within a defined environment’, a large number of studies have been devoted to their development with a remarkable evolution towards the research of an ‘ideal’ plant for a given context
This concept has been explored for apple trees, Malus × domestica, and several propositions have been formulated for promoting either dwarfed spur types (Dickman et al, 1994) or trees characterized by long and weeping branching (Type IV) which were considered prone to regular bearing (Lespinasse, 1992; Laurens et al, 2000)
We developed a strategy which made use of several models, methods and information already available from previous studies and combined them into three steps: (1) a number of geometrical and topological traits whose range of variation was previously observed within a segregating population of apple hybrids were considered as input parameters in an apple tree architectural model; (2) the 3-D representations resulting from this model were used by an environmental simulation tool to calculate light interception; and (3) a sensitivity analysis was performed on an output variable considered representative of light interception efficiency (LIE)
Summary
Since the initial proposition by Donald (1968) to develop ideotypes, ‘i.e. biological models which perform or behave in a predictable manner within a defined environment’, a large number of studies have been devoted to their development with a remarkable evolution towards the research of an ‘ideal’ plant for a given context. The concept of ideotype has been developed in crops (Peng et al, 2008; Cairns et al, 2012; Chardon et al, 2012) whereas it has remained scarce for trees In fruit trees, this concept has been explored for apple trees, Malus × domestica, and several propositions have been formulated for promoting either dwarfed spur types (Dickman et al, 1994) or trees characterized by long and weeping branching (Type IV) which were considered prone to regular bearing (Lespinasse, 1992; Laurens et al, 2000). This study aimed at providing proof that a modelling approach can contribute to this debate, by using in silico exploration of different combinations of traits and their consequences on light interception, here considered as one of the key parameters to optimize fruit tree production. Even though trait combinations and antagonism will need further investigation, the approach opens up new perspectives for breeding and genetic selection to be assisted by varietal ideotype definition
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