HERE

THE MICROVINE: AN ECOPHYSIOLOGICAL MODEL FOR GRAPEVINE
LA MICROVIGNE : UN MODELE ECOPHYSIOLOGIQUE POUR LA VIGNE
___________________________
Nathalie LUCHAIRE1,2, Mark RIENTH2,3, Laurent. TORREGROSA2, Charles ROMIEU4 A. PELLEGRINO1*
1
UMR LEPSE, 2 Place Viala, F-34060 Montpellier, France
2
UMR AGAP,2 Place Viala, F-34060 Montpellier, France
3
Fondation Jean Poupelain – Javrezac, France
*Corresponding author: A. Pellegrino, 33 (0)4 99 61 31 82, Fax: 33 (0)4 67 52 21 16, Email: [email protected]
Abstract
Microvine is a natural mutant of grapevine characterized by a dwarf, rapid cycling and continuous flowering phenotype.
Thanks to both its compacted architecture and to the continuous flowering, new insights into grapevine yield and quality
responses to climate changes are expected from this material. However, little is known regarding the main patterns of
microvine growth and development, and how they differ or not from grapevines. The present study was thus aimed at
quantifying key vegetative and reproductive characters of a reference microvine line (L1) together with the cv. Grenache N.,
and at comparing the spatial and temporal growth patterns in L1. Potted plants of L1 and Grenache N. were grown
respectively in greenhouse (2011, 2012) and outside (2009). Organs sizes were measured twice a week. Berry fresh weight
and total soluble solids were determined at harvest. Shorter internodes and smaller leaf area were observed in L1 compared
with Grenache N. Along the axis, L1 continuously held inflorescences instead of tendrils. Flowers and berries number per
inflorescence were lower in L1 than in Grenache N., and flower or berry abortion was nearly zero in L1. In spite of these
differences, phyllochrons and leaf expansion duration after leaf emergence were similar for both materials. Moreover,
maximal berry diameter and fresh weight were close for the two genotypes. A phenological model simulating leaf and berry
key developmental phases was parameterized for L1. The model was used to convert spatial leaf and berry growth dynamics
along the axis into temporal dynamics, which were compared to temporal dynamics at a given phytomer rank. The good
match between the two patterns indicated the temporal changes can be inferred from spatial patterns. These results open new
fields in grapevine studies. Short term experiment can now be designed under fully controlled environments using microvine
in order to quantify the impact of abiotic stresses on a variety of traits underlying yield or berry quality simultaneously.
Keywords: Microvine, growth, development, spacio-temporal gradient.
Résumé
La microvigne est un mutant naturel de la vigne, caractérisé par un phénotype nain, l’absence de phase juvénile et une
fructification continue. Ce nouveau matériel végétal laisse entrevoir des avancées en termes d’étude des réponses du
rendement et de la qualité de la vigne aux changements climatiques. Cependant, la croissance et le développement de la
microvigne n’ont pas encore été décrits, ni comparés à ceux de la vigne. Cette étude a pour but de phénotyper des caractères
clé du développement végétatif et reproducteur d’une lignée de référence de microvigne (L1) et du cultivar Grenache N.,
ainsi que de comparer les dynamiques de développements spatial et temporel chez L1. Des plants de L1 et de Grenache N.
en pot ont été cultivés respectivement en serre (2011, 2012) et en extérieur (2009). L’expansion des organes a été mesurée 2
fois par semaine. La masse fraiche des baies et leur taux de sucres solubles ont été déterminés à la récolte. La lignée L1
présente des entrenœuds plus courts et des feuilles plus petites que le Grenache N. Son axe principal ne porte pas de vrilles
mais uniquement des inflorescences ou des grappes. Le nombre de fleurs ou de baies est réduit chez L1 par rapport au
Grenache N., et le taux de coulure avoisine zéro. Malgré ces différences, le phyllochrone et la durée d’expansion des feuilles
après apparition de la feuille déployée sont similaires chez le Grenache N. et L1. De plus, les deux génotypes ont des
diamètre et masse de baies maximaux comparables. Un modèle simulant les stades clés de développement des feuilles et des
baies a été paramétré L1. Ce modèle a été utilisé pour convertir les dynamiques spatiales de croissance des feuilles et des
baies en dynamiques temporelles, qui ont été comparées dynamiques temporelles à un niveau de phytomère donné. La bonne
superposition entre les deux dynamiques montre que les gradients temporels peuvent être déduits des gradients spatiaux. Ces
résultats ouvrent la voie à de nouveaux types d’expérimentations sur vigne. L’impact des stress abiotiques sur l’ensemble des
composantes du rendement et de la qualité simultanément devrait pouvoir être quantifié sur microvigne via des
expérimentations de courte durée.
Mots-Clés: Microvigne, croissance, développement, gradient spatio-temporel.
1. Introduction
The adaptation of vineyard cropping systems and varieties will be a major economic issue to adapt to climate change in the
future. Assessment of grapevine yield and berry quality component responses to climatic factors require long-term
experiments, due to a stretched reproductive development over two consecutive years, succeeding an initial juvenile phase
(Ebadi et al., 1996; Yamane et al., 2006; Carmona et al., 2008). Studies under controlled environment are also made difficult
in grapevine because of large plant size. Field experiments are prone to fluctuations of all climatic factors simultaneously,
interacting with crop management, and resulting in high season to season reproductive development variability. Repeated
experiments over contrasted vintages are thus necessary (Hardie and Aggenbach, 1996; Sadras et al., 2012). But even so,
plant responses to individual climatic factors are difficult to interpret (Jones et al., 2005; Greer and Weedon, 2012).
To overcome these limitations, a natural mutant of grapevine, called microvine, was proposed by Chaïb et al. (2010). The
mutation confers to the plants a semi-dwarf stature, a rapid cycling (no juvenile phase) and a continuous flowering along the
axes. This innovative material is suitable to decipher under fully controlled environment the effect of climate at all stages of
reproductive development simultaneously (Boss et al., 2003). The present study aimed to describe microvine (Pinot Meunier
L1 line) phenology relatively to cv. Grenache N. A phenology model was parameterized for microvine in order to evaluate
the possibility to infer leaf or berry temporal developments patterns from their spatial patterns along the axis.
2. Material and methods
Plant material and growing conditions
Experiments were conducted at Montpellier SupAgro-INRA campus (southern France; 43°38N, 3°53E). Eight 3-years old
Grenache N. grafted onto 110 Richter and six 2-years old own-rooted microvines were grown outside (Grenache N; 2009) or
under greenhouse conditions (microvine; 2011-2012). Pots were filled with a mixture of sand, clay and loam (1:1:1) for
Grenache N. (5L pots), and with loam for microvines (3L pots). Plants were thinned to one main axis with no laterals. They
were drip irrigated to fit maximal evapotranspiration. Air and apex temperature was collected on each site.
Plant measurements - Budburst, flowering and veraison (onset of ripening) stages, as defined by Coombe (1995), were
recorded twice a week. Unfolded leaf number, leaf main vein and internodes lengths were measured at the same frequency.
Additional berry diameter measurements were performed on L1 with a digital caliper. Plants were harvested at cumulated
degrees days after budburst (CDD) of 1600°C d for Grenache N. and 1900° C d for L1. A base temperature of 10°C was used
for CDD calculation (Winkler and Williams, 1939). Cluster and berry number were determined at harvest, together with
berry fresh weight. Berry juice total soluble solids concentration (°Brix) was measured with a digital refractometer (Atago,
Tokyo, Japan). Individual leaf area (LA; cm²) was calculated from leaf main vein length (LL; mm) using allometric
relationships: Grenache: LA= 0.0116 LL2 - 0.0485LL; microvine: LA= 0.0096 LL2 +0.1343 LL.
Statistical analysis - Shapiro-Wilk normal distribution tests, with subsequent standard two-sided student-t or Wilcoxon
signed-rank tests, were performed for means and ajustments comparison, using R (R2.13.2, Foundation for Statistical
Computing, Vienna, Austria). Linear or non linear models were fitted from conventional least squares method. Organs sizes
and berry total soluble solids as a function of plastochron index (PI) or CDD were fitted using the model: y=M/[1+exp(-a(xxi))], where M is the maximum value of the logistic curve, a the slope at the inflexion point and xi the x value at the inflexion
point.
3. Results and discussion
Despite their semi-dwarf phenotype, microvines show similar leaf and berry growth patterns to Grenache N
Maximal internode length and leaf area in microvine ranged respectively 23 mm and 82 cm², which were half and one-third
of maximal values for Grenache N. (Fig. 1A & 1B). Decrease in internode length and leaf area after PI-20 in Grenache N.
was due to an accidental 2-days water deficit at PI-40 emergence. In accordance with previous observations on Grenache N.
(Lebon et al., 2004), the microvine displayed a ternary rhythmicity in internode length, with phytomers bearing
inflorescences (P1, P2) being longer than phytomers with no inflorescence (P0) (Fig. 1A). As described by Chaib et al.
(2010), the semi-dwarf phenotype in Pinot meunier L1 plants was associated to a continuous flowering along the main axis
(Fig. 1C). By contrast, Grenache N. held on average 2 inflorescences, which were located in the 8 pre-formed phytomers of
the axis. An average of 40 flowers or berries per cluster was observed in the microvine. Berries number was 4-fold higher in
Grenache N., with about 150 berries per cluster. Flower and berry abortions reached an average rate of 1% for microvine and
51% for Grenache N. (data not shown). These berries number or abortion rate for Grenache N. were in the range of
observations for other cv. (Shavrukov et al., 2003; Lebon et al., 2005). Similarly to grapevine, microvine berry development
could be described from 2 sigmoidal berry growth phases (I, III), which were separated by a lag phase (II) ending with
beginning of veraison and the accumulation of sugar in berries (Fig. 1D, 1E & 1F) (Coombe, 1995; Ojeda et al., 1999).
Maximum berry diameter, berry fresh weight and soluble sugars at harvest were not significantly different between
microvine and Grenache N. (P<5%), reaching about 11.6 mm for berry diameter, 1.2 g for berry fresh weight and 17.4 °Brix
for soluble sugars. Similar berry size values but higher total soluble solids at harvest were reported for grapevine in the
literature (Kliewer and Torres, 1972; Ojeda et al., 1999; Pellegrino et al., 2008).
Key leaf and berry development phases can be timed from a phenological model in microvine, similarly to Grenache N
A phenological model accounting for microvine leaf and berry developments from CDD was parameterized and compared to
Grenache N. The numbers of phytomers with - unfolded leaves (Nul); fully expanded leaves (defined from 95% of maximum
leaf area; Nel); inflorescences beyond 50% of flowering (Nflo); clusters beyond start of phase I (defined from 5% of
maximum berry diameter within phase I; NbI); clusters beyond start of phase II (defined from 95% of maximum berry
diameter within phase I; NbII) – were all linearly correlated to CDD. The two years (2011-2012) did not differ (P<5%) and
were thus averaged. Phyllochron calculated from Nul fitting line was 24°C d for microvine, close to the value of 22°C d
reported for Grenache N. by Lebon et al. (2004). A constant 220°C d period for leaf expansion after leaf emergence
emergence ([Nul to Nel]) was observed in microvine, which was also in the range of values observed in Grenache N. Due to
the heterogeneity in flower and berry development among the clusters, berry expansion started from 84 to 54 °C d before
50% flowering ([NbI to Nflo]), for phytomer 10 and 40 respectively. The period between leaf emergence and berry growth
start ([Nul to NbI]) ranged from 350 to 334°C d, and berry growth duration (phase I; [NbI to NbII]) from 320 to 601 °C d, for
phytomers 10 to 40. Such a variability in the duration of berry growth phase fits with observations in Syrah (Ojeda et al.,
1999).
Temporal leaf and berry developments can be inferred from spatial patterns along the axis in microvines
The phenology model parameterized above was used to compare spatial leaf area and berry diameter (phase I) to temporal
development pattern in microvines. Temporal changes measured in 2011 were compared to fitted spatial patterns along the
main axis shown in Fig. 1B & 1D for 2011-2012 data sets (Fig. 3). For this purpose, PI values in Fig. 1B & 1D were
converted into CDD using the phyllochron: Thermal time from phytomer emergence (°Cd) = PI * 24.39 [phyllochron (°Cd)].
Similar spatial and temporal growth patterns were shown for both leaf area and berry diameter. Temporal growth patterns
inferred from this spatial distribution correctly predicted the actual temporal growth pattern for both leaf area and berry
diameter. These results suggest that a single assessment of the spatial pattern of leaf, flower and berry traits along the main
axis after a period of environmental stress may provide insightful information on the impact of that stress on a series of
developmental variables simultaneously.
4. Conclusions
The microvine shares with grapevine key vegetative and reproductive developmental traits. The possibility to infer temporal
developmental patterns from spatial observations on the axis open new fields in grapevine studies based on the use of the
microvine. Short term experiments may be designed under fully controlled environments in order to quantify the impact of
abiotic stresses on all yields and quality components simultaneously.
5. Acknowledgments
This study was supported by ANR-Genopole (project ANR-2010-GENM-004-01) and the Poupelain foundation.
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Figure 1: (A) Internode length, (B) leaf area, (C) flower or berry number, (D) berry diameter, (E) berry fresh weight and (F) berry total
soluble solids (TSS) plotted as a function of plastochron index on L1 (2011, ; 2012, ▲) and Grenache N. (2009, ). Each point is the
average of 6 plants (L1) or 8 plants (Grenache N.). The 50% flowering stage (dotted vertical lines) is delimited together with the 3 phases of
berry development for L1. Bars indicate average standard deviation per genotype. Inset in A shows periodicity in phytomers internode
length.
Figure 1 : (A) Longueurs des entrenœuds, (B) surface foliaire, (C) nombre de fleurs ou de baies, (D) diamètre des baies, (E) masse fraîche
des baies et (F) concentration en sucre soluble (TSS) en fonction de l’indice plastochronique pour L1 (2011, ; 2012, ▲) et Grenache N.
(2009, ). Chaque point correspond à la moyenne de 6 plantes (L1) ou 8 plantes (Grenache N.). Le stade 50% floraison (ligne en pointillés)
et les 3 phases de développement des baies sont délimités pour L1. Les barres représentent l’écart type moyen par genotype. L’insert dans A
montre la rythmicité de longueur des entrenœuds.
Figure 3: Temporal changes in (A) leaf area and (B) berry diameter plotted as a function of thermal time from phytomer emergence for the
microvine (2011, ). Fitting lines represent spatial adjustments calculated from Fig. 1B & 1D. Each point corresponds to one leaf (A) and
the mean of 10 berries per cluster (B).
Figure 3 : (A) Evolutions temporelles de (A) la surface foliaire et (B) le diamètre des baies en fonction du temps thermique cumulé après
l’apparition du phytomère pour la microvigne (2011, ). Les lignes représentent les ajustements spatiaux calculés à partir des Fig. 1B & 1D.
Chaque point correspond à une feuille (A) et la moyenne de 10 baies au sein d’une grappe (B).