Oscar Grillo

Morphological characterisation of Vitis vinifera L. seeds by image analysis and comparison with archaeological remains

In archaeobotanical studies, the taxonomic classification of diaspores has usually been done by simple morphological observation and visual comparison with ex situ collections of seeds, although the use of biometric indices has often proved to be a powerful approach in the taxonomic studies of the genus Vitis as well as for the species attribution of archaeological remains. Using image analysis techniques, seeds from two Sardinian archaeological sites, the pre-Nuragic and Nuragic complex of Sa Osa in central-western Sardinia, attested as the oldest Sardinian archaeological site with remains of Vitis seeds, and the Isola di Coltellazzo in southwest Sardinia, were selected and characterized on the basis of morphological features and Elliptic Fourier Descriptors. Moreover, seeds of five modern populations of V. vinifera ssp. sylvestris collected from southwest Sardinia and the seeds of 41 cultivars of V. vinifera ssp. vinifera mainly from southern and central-western Sardinia were also analysed by computer image analysis. The obtained data were used to implement a database of biometric parameters and to compare the unknown archaeological seeds with the characterized recent seeds, using Linear Discriminant Analysis. The similarity of the archaeological seeds to V. vinifera ssp. vinifera cultivars rather than to V. vinifera ssp. sylvestris populations could allow it to be stated that, between the Middle and Final Bronze Age, varieties very close to modern V. vinifera ssp. vinifera were already being used to produce wine and/or to be preserved for foodstuffs. Moreover, the better matching of the archaeological seeds to white grapes rather than black grape cultivars could indicate the origins of the traditional cultivation of white grapes in these regions of Sardinia.

Seed image analysis and taxonomy of Diplotaxis DC. (Brassicaceae, Brassiceae)

The genus Diplotaxis, comprising 32 or 34 species, plus several additional infraspecific taxa, displays a considerable degree of heterogeneity in the morphology, molecular markers, chromosome numbers and geographical amplitude of the species. The taxonomic relationships within the genus Diplotaxis were investigated by phenetic characterisation of germplasm belonging to 27 taxa of the genus, because there is an increasing interest in Diplotaxis, since some of its species (D. tenuifolia, D. muralis) are gathered or cultivated for human consumption, whereas others are frequent arable weeds (D. erucoides) in many European vineyards. Using a computer-aided vision system, 33 morpho-colorimetric features of seeds were electronically measured. The data were used to implement a statistical classifier, which is able to discriminate the taxa within the genus Diplotaxis, in order to compare the resulting species grouping with the current infrageneric systematics of this genus. Despite the high heterogeneity of the samples, due to the great intra-population variability, the stepwise Linear Discriminant Analysis method, applied to distinguish the groups, was able to reach over 80% correct identification. The results obtained allowed us to confirm the current taxonomic position of most taxa and suggested the taxonomic position of others for reconsideration.

Computer vision as a method complementary to molecular analysis: Grapevine cultivar seeds case study

Despite different breeding events, as well as the domestication phenomena which contributed to enrich the grape varietal heritage in Sardinia, many local varieties simply are the product of linguistic distorting due to the wide heterogeneity historic-cultural of the island. This phenomenon generated a great assortment of grape names, that, together with the huge real number of cultivars, is the cause of the incredible current grapevine Sardinian panorama. The goal of this article is to compare the published molecular data of 40 Sardinian autochthonous cultivars with the results achieved by the germplasm phenotypical characterization, on the basis of morpho-colorimetric features and Elliptic Fourier Descriptors (EFDs), measured by image analysis. Statistical classifiers were implemented to discriminate dissimilar seeds and carry out hypothetical synonymy groups to compare with those proposed on the basis of Simple Sequence Repeat (SSR) markers. This work represents the first trial to validate a morpho-colorimetric characterization method by direct comparison with molecular data, proving that the 113 measured features of the germplasm resulted adequate to achieve a clear discrimination among the synonymy groups.

Identification of Sardinian Species of Astragalus Section Melanocercis (Fabaceae) by Seed Image Analysis

Using a computer-aided imaging system, the seed morphometric and colorimetric features of Astragalus terraccianoi, A. tegulensis and A. thermensis — all belonging to Astragalus sect. Melanocercis — were measured and analysed. The results confirmed differences between A. terraccianoi and A. tegulensis, as well as the validity of A. tegulensis. Differences between the Corsican and Sardinian populations of A. terraccianoi were also found.

Inter- and intraspecific morphometric variability in Juniperus L. seeds (Cupressaceae)

In this study, a statistical classifier for Mediterranean taxa of Juniperus, based on 98 seed morphometric parameters, was tested at interspecific, specific and intraspecific levels. Ripe cones of 10 taxa were collected in different regions of the Mediterranean Basin to compare and discuss their taxonomic treatments according to two different sources. High percentages of correct identification were reached for both taxonomic treatments at the specific and intraspecific level and from the comparison among taxa of the J. oxycedrus, J. communis and J. phoenicea complexes. Moreover, ripe cones of J. macrocarpa were collected from four Sardinian populations, in two seasons, and from plant and soil, in order to analyse inter-population, seasonal and source variability in seed morphology. This statistical classifier discriminated J. macrocarpa seeds collected in spring more accurately than those collected in autumn, but it failed to distinguish between the seeds collected from plants and soil, or between those collected from different populations of the same geographic region.

Seed image analysis provides evidence of taxonomic differentiation within the Medicago L. sect. Dendrotelis (Fabaceae)

Morpho-colorimetric quantitative variables describing seed size, shape, colour and texture were analysed using image analysis techniques, in order to evaluate the variability among Medicago taxa sect. Dendrotelis and verify the current taxonomic treatment which divides this section into three species: M. arborea L., M. citrina (Font Quer) Greuter and M. strasseri Greuter, Matthäs & H. Risse. Further comparisons were conducted to discriminate among populations and regions of provenance. Data obtained were statistically analysed applying stepwise Linear Discriminant Analysis method (LDA), recording an overall cross-validated classification performance of 100% at species level. With regard to inter-population comparisons, percentages of correct discrimination above 98% were achieved and high performance was recorded in the discrimination among M. arborea taxa distinguished by region of provenance. For each of these statistical comparisons, the best discriminant variables chosen by the stepwise LDA were related to colour and textural information. Finally, the obtained results confirmed the validity of the proposed method to be highly diagnostic in the statistical assessment of the morpho-colorimetric traits variability of Medicago taxa seeds, both for the taxonomic differentiation at species level and regional and population groups.

Predictive method for correct identification of archaeological charred grape seeds: Support for advances in knowledge of grape domestication process

The identification of archaeological charred grape seeds is a difficult task due to the alteration of the morphological seeds shape. In archaeobotanical studies, for the correct discrimination between Vitis vinifera subsp. sylvestris and Vitis vinifera subsp. vinifera grape seeds it is very important to understand the history and origin of the domesticated grapevine. In this work, different carbonisation experiments were carried out using a hearth to reproduce the same burning conditions that occurred in archaeological contexts. In addition, several carbonisation trials on modern wild and cultivated grape seeds were performed using a muffle furnace. For comparison with archaeological materials, modern grape seed samples were obtained using seven different temperatures of carbonisation ranging between 180 and 340ºC for 120 min. Analysing the grape seed size and shape by computer vision techniques, and applying the stepwise linear discriminant analysis (LDA) method, discrimination of the wild from the cultivated charred grape seeds was possible. An overall correct classification of 93.3% was achieved. Applying the same statistical procedure to compare modern charred with archaeological grape seeds, found in Sardinia and dating back to the Early Bronze Age (2017–1751 2σ cal. BC), allowed 75.0% of the cases to be identified as wild grape. The proposed method proved to be a useful and effective procedure in identifying, with high accuracy, the charred grape seeds found in archaeological sites. Moreover, it may be considered valid support for advances in the knowledge and comprehension of viticulture adoption and the grape domestication process. The same methodology may also be successful when applied to other plant remains, and provide important information about the history of domesticated plants.

First finds of Prunus domestica L. in Italy from the Phoenician and Punic periods (6th-2nd centuries BC)

During the archaeological excavations in the Phoenician and Punic settlement of Santa Giusta (Oristano, Sardinia, Italy), dating back to the 6th–2nd centuries bc, several Prunus fruitstones (endocarps) inside amphorae were recovered. The exceptional state of preservation of the waterlogged remains allowed morphometric measurements to be done by image analysis and statistical comparisons made with modern cultivated and wild Prunus samples collected in Sardinia. Digital images of modern and archaeological Prunus fruitstones were acquired with a flatbed scanner and analysed by applying image analysis techniques to measure 26 morphometric features. By applying stepwise linear discriminant analysis, a morphometric comparison was made between the archaeological fruitstones of Prunus and the modern ones collected in Sardinia. These analyses allowed identification of 53 archaeological fruitstones as P. spinosa and 11 as P. domestica. Moreover, the archaeological samples of P. spinosa showed morphometric similarities in 92.5% of the cases with the modern P. spinosa samples currently growing near the Phoenician and Punic site. Likewise, the archaeological fruitstones identified as P. domestica showed similarities with the modern variety of P. domestica called Sanguigna di Bosa which is currently cultivated near the village of Bosa. Currently, these findings represent the first evidence of P. domestica in Italy during the Phoenician and Punic periods.

Morpho‐colorimetric characterisation of Malva alliance taxa by seed image analysis

Seed morphometric and -colorimetric features describing shape, size and textural seed traits of 28 taxa belonging to the genera Lavatera L. and Malva L., were recorded by means of computer vision techniques. The data were statistically analysed to contribute to the taxonomical treatment of the Malva alliance and to assess some doubtful systematic positions. A clear differentiation between taxa traditionally attributed to Lavatera or Malva was highlighted. Furthermore, the identification system proposed here was able to discriminate among the Lavatera sections, confirming the taxonomic organization of this genus. The results obtained for Malva, both at the species level and among sections, supported this analytical tool as diagnostic for systematic purposes.

Effectiveness of a computer vision technique in the characterization of wild and farmed olives

Olive endocarps biometric features were measured by image analysis techniques.Relationships among wild olive populations, ancient trees and cvs were studied.The two O. europaea varieties (var. europaea and sylvestris) were discriminated.A high degree of phenotypic variability was find in wild populations.The allochthonous origin of local varieties is confirmed. Existing in two forms, namely the wild and the cultivated one, the olive tree (Olea europaea L.) is one of the most widespread species in the Mediterranean Basin since the sixth millennium B.C. According to the theory of a polycentric origin for domestication, mainly supported by the presence of the wild form all over the Mediterranean area, the goal of this study is to use endocarps biometric features, measured by image analysis techniques, in order to investigate the relationships among different Sardinian wild olive populations, ancient olive trees and olive cultivars. A total of 137 morphometric, colorimetric and textural characters were measured on each of the 2842 studied endocarps. The morpho-colorimetric analysis of olive endocarps proved the effectiveness of the technique to discriminate between the two currently recognized O. europaea L. varieties (var. europaea and var. sylvestris). The partial overlapping that resulted between wild and ancient olives suggests the existence of large populations characterized by a high degree of phenotypic variability. Similar results were reached for varietal discrimination, perfectly fitting with previous findings of molecular studies. Considering the phenotypic and genetic distance of cultivars from autochthonous wild olives, the allochthonous origin of local varieties is furthermore confirmed.