Corner's rules as a framework for plant morphology, architecture and functioning - issues and steps forward

International audienc

Adapting apple ideotypes to low-input fruit production agro-ecosystems

Current commercial apple growing is highly dependent on off-farm inputs and it is urgent to develop new strategies to remedy this situation. The challenge for the future is to achieve lower-input apple orchards, whether under Integrated Fruit Production (IFP) or Organic Fruit Production (OFP) systems. This paper analyses the different agronomic factors that play key roles both in the current and future ‘More Sustainable Orchard’, with particular attention on plant protection. Firstly, the concept of ‘ideotype’ is developed, emphasizing the most important characteristics of optimal ideotypes for apple. Secondly, current knowledge on the relationships between genotype, cultural practices and the environment is presented and discussed. This paper deals with properties that need to be combined at plant material and orchard levels to optimise the IFP and OFP low-input systems. The focus is on: (a) the main characteristics of apple ideotypes; (b) breeding strategies; and (c) adapted cultural practices and control measures in the orchards

Effects of shoot bending on lateral fate and hydraulics: invariant and changing traits across five apple genotypes

Correspondance:[email protected] aim of this work was to study the variability of physiological responses to bending and the relationship with hydraulic conductance of the sap pathway to the laterals for five apple genotypes. The study focuses on the fate of the laterals. The genetic variability of bending can have two sources: a genetic variability of stem geometry which can lead to differences in mechanical state; and a genetic variability of sensitivity to bending. Since the aim was to check if some genetic variability of sensitivity to bending exists, the genetic variability of shoot geometry was taken into account. To do so, bending was controlled by imposing different bending intensities using guides of different curvature conferring a similar level of deformation to the five genotypes. Bending was done either in the proximal zone or in the distal zone of shoots, in June and in the following winter, respectively. A Principal Component Analysis comparing upright and bent shoots revealed that bending in the proximal zone stimulated vegetative growth of buds which would otherwise stay latent. A second Principal Component Analysis restricted to bent shoots revealed that bending increased the abortion of laterals in the lower face of the shoots. The abortion phenomenon was to the detriment of sylleptic laterals or of inflorescence, depending on the genotype. There was a strong effect of position around the shoot on within-shoot hydraulics. Hydraulic conductance was significantly decreased in the lower face of the shoot bent in winter. This result suggested a causal relationship between this phenomenon and lateral abortion

Are the effects of winter temperatures on spring budburst mediated by the bud water status or related to a whole-shoot effect? Insights in the apple tree

UMR 1334 AGAP : Equipe AFEF ‘Architecture et Fonctionnement des Espèces fruitières’The effects of winter temperatures, i.e., during dormancy, on shoot architecture are well known with budburst preferentially in the distal or the proximal part of the parent shoot in cold and mild winter conditions, respectively. However, the link with the overwintering bud water status is still scarcely documented. Our study was developed on four apple (Malus domestica Borkh.) cultivars covering a range of chilling requirements from low (‘Condessa’) to medium (‘Granny Smith’) and high (‘Royal Gala’, ‘Starkrimson’), and maintained in either cold (1,428 h below 7.2 °C) or mild (99 h below 7.2 °C) fluctuating winter temperatures. Our aim was to analyze xylem conductance at the stem-to-bud junction, and relative water content and water potential of the bud itself, for buds situated in the distal third of one-year-old shoots. From dormancy to the pre-budburst stage, xylem conductance at the stem-to-bud junction increased or decreased or did not show consistent changes depending on the cultivar and the winter temperature treatment. Whatever the cultivar, there were no significant trends across dates for the effects of winter temperatures on bud water potential and relative water content. Water potential had negative values, between −4.35 and −2.24 MPa, across cultivars and winter temperature treatments without a consistent relationship with actual spring budburst frequency. These results suggested that lateral buds were hydraulically isolated from the parent stem during winter until a few days before budburst. We discussed that the temperature-related spring budburst was likely more related to a whole-shoot effect mediated by hormonal, hydraulics and/or sugar signaling, than to the individual bud water status during dormancy