Genotypic differences in architectural and physiological responses to water restriction in rose bush

Abstract

The shape and, therefore, the architecture of the plant are dependent on genetic and environmental factors such as water supply. The architecture determines the visual quality, a key criterion underlying the decision to purchase an ornamental potted plant. The aim of this study was to analyze genotypic responses of eight rose bush cultivars to alternation of water restriction and re-watering periods, with soil water potential of -20 and -10 kPa respectively. Responses were evaluated at the architectural level through 3D digitalization using six architectural variables and at the physiological level by measuring stomatal conductance, water content, hormones [abscisic acid (ABA), auxin, cytokinins, jasmonic acid, and salicylic acid (SA)], sugars (sucrose, fructose, and glucose), and proline. Highly significant genotype and watering effects were revealed for all the architectural variables measured, as well as genotype × watering interaction, with three distinct genotypic architectural responses to water restriction - weak, moderate and strong - represented by Hw336, 'Baipome' and 'The Fairy,' respectively. The physiological analysis explained, at least in part, the more moderate architectural response of 'Baipome' compared to 'The Fairy,' but not that of Hw336 which is an interspecific hybrid. Such physiological responses in 'Baipome' could be related to: (i) the maintenance of the stimulation of budbreak and photosynthetic activity during water restriction periods due to a higher concentration in conjugated cytokinins (cCK) and to a lower concentration in SA; (ii) a better resumption of budbreak during the re-watering periods due to a lower concentration in ABA during this period. When associated with the six architectural descriptors, cCK, SA and ABA, which explained the genotypic differences in this study, could be used as selection criteria for breeding programs aimed at improving plant shape and tolerance to water restriction.

Keywords: Rosa; architectural analysis; genotype × environment interaction; hormones; water restriction tolerance.

FIGURE 1

Plant photography before phenotyping by 3D digitalization (A); plant architecture with two components (metamer and axis; B); simplified representation with three branching orders: Order 1 (O1), Order 2 (O2), and Order 3 (O3; C).

FIGURE 2

Application of the water restriction (WR) treatment based on developmental stage of the primary axis [bud burst of the rooted cutting, visible flower bud of the order 1 axis (VFB1), visible flower bud of the order 2 axes (VFB2) and elementary architectural structure (EAS) stage]. 14-days (14d) periods of water restriction (WRP1 and WRP2) are indicated by dotted lines and periods of re-watering (WWP1 and WWP2) by continuous lines.

FIGURE 3

Mean of six architectural variables measured on control plants and plants subjected to a water restriction (WR) treatment of eight rose genotypes. Mean and standard error (SE) of 10 plants per genotype and treatment are shown.

FIGURE 4

Intensity of the architectural response per genotype.

FIGURE 5

Stomatal conductance (g_s) during water restriction (WRP) and re-watering (WWP) periods. All measurements were carried out on the two youngest leaves completely developed of control plants and plants subjected to a WR treatment for the three genotypes ‘Baipome’ (A). ‘The Fairy’ (B), and Hw336 (C). Hatched bars indicate WRP1 and WRP2 periods and closed bars indicate WWP1 and WWP2 periods. A double line (||) delimits the 15-days period after each re-watering. Mean and SE of five plants per genotype and treatment are shown.

FIGURE 6

Circles of correlations of the principal components 1 (PC1) and 2 (PC2) of the principal component analysis (PCA) built using 12 physiological variables. The variables were measured during WRP1 and WRP2 periods (A) and during WWP1 and WWP2 periods (B).