Corresponding author: Emilio Cervantes (
Academic editor: Denis Rusjan
New methods of image analysis may contribute to the morphological description of seed shape and cultivar classification in Ampelography. We recently proposed a method based on the comparison of seed images with geometric figures, defined by mathematical equations for the identification and classification of grapevine cultivars. Representative cultivars of
Ampelography, curvature, geometry, grapevine, morphology, beak, shape, taxonomy
The description, classification and phylogenetic relationships of grape cultivars belong to Ampelography, a discipline traditionally based on the analysis of morphological characters (
In a recent study with 38 cultivars of the IMIDRA collection, ten groups were proposed according to the similarity of their seeds with geometric figures (
We present here a new method to describe and quantify seed shape in the
The curvature of a plane curve is a parameter which measures how the direction (slope) of the curve changes along the successive points (
The thirty eight cultivars used in this study are presented in Tables
Photographs were taken with a camera Nikon D80 of 10.2 megapixels. The images containing 30 seeds per cultivar were described in
Seed images were inserted in Mathematica files (.nb). The analysis of curvature comprised two parts. First, it was applied to whole seed images. Points were taken along the seed silhouettes and the corresponding Bézier Curves were obtained. The maximum curvature values, corresponding to the beak tip, were calculated according to Tocino and Cervantes (
Difficulties encountered with the application of this protocol derive from structural aspects of
This section is divided in five parts: Curvature analysis in whole seeds; seed size, shape and peduncle structure in
Fig.
The seeds of CA 13.4, CA 13.6 and SE 2.1 were colected from wild populations close to the Nateruela stream in Cádiz and river Huéznar in Seville respectively. They are smaller and more regularlyshaped (rounded or ovoid) than the seeds of the majority of cultivars used in Viticulture. Seed shape in these three varieties adapts well to a model oval or pyriform, with an elongated part corresponding to the beak that gives them the apparence of a fig
Cultivars Dominga, Teta de vaca and Verdejo are in the same group in the classification by similarity to geometric models (
A similar variation is observed in cultivars Bobal, Hebén and Moscatel de grano menudo. Thus, Bobal and Hebén share with varieties in the Teta de vaca groups two characters: 1) The presence of seeds of a triangular shape, and 2) Two kinds of seeds by the shape of their apex. The first of these two aspects is also shared by Airén. Group Airén includes Airén, Bobal and Mazuela, and the relatively close values of aspect ratio make the two groups of Teta de Vaca and Airén closely related.
The curvature analysis gave a constant pattern in these varieties whose beak is represented by a curve with maximum curvature in a single point (Fig.
The images of the beaks in these cultivars end in a slightly convex, often almost flat upper line. The corresponding curves have in general two maximum values of curvature (Fig.
Recently, we proposed a classification of 38 cultivars of
In the majority of the cultivars, the seeds had their pedicels flat at their apex. In consequence, representations of Bézier of their profiles had a plane form with two maximum curvature values. This type was observed in a total of 23 cultivars, including all but one of the 23 cultivars in four groups and with the addition of Airén. The cultivars with a flat pedicel are predominant in groups Listán Prieto (Listán Prieto and Tortozona Tinta), Albillo Real (Alarije, Albillo Real, Cayetana Blanca, Graciano, Juan García and Tempranillo), eleven of the twelve cultivars of group Moscatel (all of them except Moscatel de grano menudo), the three cultivars of group Doña Blanca (Doña Blanca, Monastrell and Pedro Ximénez) and Airén. Thus, morphological groups, Listán Prieto, Albillo Real, Moscatel and Doña Blanca, share in common the property of a peduncle plane at the top, whose Bézier representation presents two maximum curvature values. In consequence, these four groups constitute a series, ordered by decreasing values of Stummer Index from Listán Prieto to Doña Blanca. The remaining six groups of the morphological classification have varying proportions of plane and acute peduncles.
The seeds having their apex acute belong to six cultivars in four groups: Hebén (Macabeo and Zalema, but not Hebén itself), Tortozón (Imperial and Tortozón), Airén (Mazuela) and de Cuerno.
Nine cultivars remain to complete the total of 38 used in this work. These are the three
Wild type seeds have particular morphological aspects. They are of reduced size and with a small beak and, in consequence, their images have high values of roundness and Stummer Index with low Aspect Ratio (
Cultivars Dominga, Teta de vaca and Verdejo share a triangular shape and contain seeds of the two types: acute and plane at the top of the peduncle. The presence of the two morphological types is also a characteristic of Bobal, Hebén and Moscatel de grano menudo.
Curvature analysis allows us to discriminate amongst cultivars that gave similar results with the analysis based on geometric models. Thus, Macabeo and Zalema grouped with Hebén in the analysis of seed shape by comparison with geometric models. The curvature analysis in the beak gave a constant pattern consisting of a single curve with maximum curvature defined in a single point of maximum curvature values for Macabeo and Zalema, while there is a mixture of types (single and double maximum curvature values) in different seeds of Hebén.
The process of domestication of
The morphological difference between the seeds of wild grapes and cultivars of
Conversion of a seed peduncle image to the corresponding Bézier Curve and calculation of the curvature values. Seed images were inserted in Mathematica notebook (.nb). A set of points was marked on the profile of their beaks (left). The coordinates of the points were obtained and run in a programme (
A seed image was converted to the corresponding Bézier Curve and the curvature values calculated. Seed images were inserted in Mathematica notebook (.nb) and a set of points was marked defining the profile of the whole seed (left). The coordinates of the points were obtained (b) and run in a programme (
Seed images and graphic representation of curvature values in whole seeds of:
Seed images and curvature values in whole seed images of:
Seed images and curvature values in the seed peduncle of wildtype cultivars (Sylvestris group):
Seed images and curvature values in the seed peduncle of cv. Teta de Vaca.
Seed images and curvature values in the seed peduncle of (cultivars from top to bottom):
Seed images and curvature values in the seed peduncle of cultivars:
List of cultivars used in this work with the ampelographic description of their seeds, based on the OIV "Descriptor List for Grape varieties and

OIV241 
OIV242 
OIV243 
OIV244 

Airén  3  5  3  1 
Alarije  3  3  3  1 
Albillo Real  3  3  5  1 
Beba  3  3  5  1 
Bobal  3  5  3  1 
Bruñal  3  3  3  1 
Caíño Tinto  3  5  3  1 
Castellana Blanca  3  5  5  1 
Cayetana Blanca  3  5  3  1 
De Cuerno  3  9  3  1 
Dominga  3  5  5  1 
Doña Blanca  3  5  3  1 
Garnacha Tinta  3  3  2  1 
Gewürztraminer  3  3  3  1 
Graciano  3  3  3  1 
Hebén  3  5  5  1 
Imperial  3  3  5  1 
Juan García  3  5  5  1 
Listán Prieto  3  3  5  1 
Macabeo  3  3  3  1 
Malvasía Aromática  3  5  3  1 
Mazuela  3  3  3  1 
Mollar Cano  3  5  5  1 
Monastrell  3  5  5  1 
Moscatel de Alejandría  3  3  5  1 
Moscatel de Grano Menudo  3  3  3  1 
Palomino Fino  3  3  3  1 
Pedro Ximénez  3  5  3  1 
Prieto Picudo  3  3  3  1 
Sylvestris CA 13,4  3  3  3  1 
Sylvestris CA 13,6  3  3  3  1 
Sylvestris SE 2,1  3  3  2  1 
Tempranillo  3  3  3  1 
Teta de Vaca  3  5  3  1 
Tortozón  3  5  3  1 
Tortozona Tinta  3  3  7  1 
Verdejo  3  5  3  1 
Zalema  3  3  3  1 
Groups of cultivars according to their similarity with morphological models. The groups are ordered by increasing aspect ratio (length/width). Underlined: cultivars used in the whole seed curvature analysis. Between parenthesis: Number of seeds used in the peduncle curvature analysis.


Listán Prieto  Listán Prieto (15), Tortozona Tinta (15) 
Sylvestris  CA 13.4 (29), CA 13.6 (30), SE 2.1 (30) 
Albillo Real  Alarije (29), Albillo Real (30), Cayetana Blanca (10), Graciano (15), Juan García (10), Tempranillo (10) 
Hebén  Hebén (30), Macabeo (30), Zalema (30) 
Moscatel  Beba (12), Bruñal (15), Caíño Tinto (10), Castellana Blanca (30), Garnacha Tínta (30), Gewürztraminer (15), Malvasía Aromática (15), Mollar Cano (15), Moscatel de Alejandría (15), Moscatel de Grano Menudo (14), Palomino Fino (20), Prieto Picudo (15) 
Tortozón  Imperial (30), Tortozón (30) 
Teta de Vaca  Dominga (30), Teta de Vaca (30), Verdejo (30) 
Doña Blanca  Doña Blanca (5), Monastrell (13), Pedro Ximénez (20) 
Airén  Airén (30), Bobal (20), Mazuela (39) 
De Cuerno  De Cuerno (5) 