Using 20 SSR markers well scattered across the 19 grape chromosomes, we analyzed 4,370 accessions of the INRA grape repository at Vassal, mostly cultivars of Vitis vinifera subsp. sativa (3,727), but also accessions of V. vinifera subsp. sylvestris (80), interspecific hybrids (364), and rootstocks (199). The analysis revealed 2,836 SSR single profiles: 2,323 sativa cultivars, 72 wild individuals (sylvestris), 306 interspecific hybrids, and 135 rootstocks, corresponding to 2,739 different cultivars in all. A total of 524 alleles were detected, with a mean of 26.20 alleles per locus. For the 2,323 cultivars of V. vinifera, 338 alleles were detected with a mean of 16.9 alleles per locus. The mean genetic diversity (GDI) was 0.797 and the level of heterozygosity was 0.76, with broad variation from 0.20 to 1. Interspecific hybrids and rootstocks were more heterozygous and more diverse (GDI = 0.839 and 0.865, respectively) than V. vinifera cultivars (GDI = 0.769), Vitis vinifera subsp. sylvestris being the least divergent with GDI = 0.708. Principal coordinates analysis distinguished the four groups. Slight clonal polymorphism was detected. The limit between clonal variation and cultivar polymorphism was set at four allelic differences out of 40. SSR markers were useful as a complementary tool to traditional ampelography for cultivar identification. Finally, a set of nine SSR markers was defined that was sufficient to distinguish 99.8% of the analyzed accessions. This set is suitable for routine characterization and will be valuable for germplasm management.
Texture analysis is a well-established analytical technique in the food industry for evaluating the mechanical and physical characteristics of both raw ingredients and finished products. Instrumental mechanical properties of table grapes, acquired using universal testing machines equipped with specific probes, may be of interest in the viticulture and postharvest sectors to recognize the potential of each variety and help satisfy market requirements. The measured parameters are related to some sensory properties and, therefore, indirectly to consumer acceptability of the product. As texture analysis is a rapid and low-cost analytical technique, it can also be favorably applied in enology as a routine tool for monitoring winegrape quality. Among the different mechanical parameters measurable, berry skin thickness and hardness are indices that reflect anthocyanin extractability and dehydration kinetics with adequate reliability. This review collects the most recent research results from grape texture studies, emphasizes the potentiality and limits of this analytical technique when applied to grape studies, and highlights trends that require further understanding.
There is scant literature on the assessment and validation of methods for monitoring grape texture during ripening. There is a distinct lack of information from published work on the correct procedures to set up texture method. If the measurement of grape texture is to be used for assessing ripeness and further extended to the assessment of polyphenol extractability potential, the relationship between physicochemical parameters and sensory descriptors should be evaluated as a matter of importance. In this work, the physical properties of grape texture during ripening were addressed by an assessment of the relationship between the methods of double compression and puncture tests. The second part of the study reported here applied the methods developed in the first year to grapes sampled in the following year. The results showed that the mechanical texture measurements were able to discriminate grapes coming from different parcels and correlations were found between texture parameters and sensory descriptors. PRACTICAL APPLICATIONSThis paper defines the measurement conditions for monitoring grape texture, particularly during ripening. These established methodologies provide enologists with the tools to monitor the progress of grape maturity, and these mechanical methods compare favorably with the expensive and timeconsuming classical methods. These established methodologies could also be 1 Corresponding Journal of Texture Studies 40 (2009) 511-535. © 2009 used to highlight important information on grape evolution during ripening and help to provide better insight on the choice of the preferred/ideal harvest date. These tools, providing enologists with data on the evolution of fruit texture, could be used to help select more suitable winemaking processes as well, as the extractability of compounds present in the fruit is probably linked to its texture.
In an attempt to develop a technique for the identification of grape cultivars in commercial wines, a method for the extraction of DNA from must and experimental wines was adapted and optimal PCR conditions for the amplification of this DNA were established. DNA was analyzed during the fermentation process for six cultivars (Chardonnay, Clairette blanche, Grenache noir, Merlot, Muscat blanc à petits grains, and Syrah). The extractions were performed on solid parts in suspension as well as on the aqueous fraction. Expected profiles for these cultivars were obtained with DNA extracted from the solid parts during all of the fermentation process and for the wine. The analysis of DNA extracted from aqueous fractions was less reproducible, and microsatellite amplifications were obtained only in the case of Clairette blanche, Merlot, and Syrah wines. Results demonstrate that the purification process is adequate for the analysis but that the DNA concentration represents the main limiting factor. Technical improvements of the method are discussed. Keywords: Microsatellite; DNA; grape must; monovarietal wine; varietal characterization
Because wine quality highly relies on the varietal composition of the must, the development of methods allowing the authentication of varieties in musts and wines would be of great value as a guarantee of quality. Microsatellite markers have already been applied to the authentication of grape juices (Faria, M. A.; Magalhães, R.; Ferreira, M. A.; Meredith, C. P.; Ferreira Monteiro, F. J. Agric. Food Chem. 2000, 48, 1096-1100) and to the analysis of experimental wines (Siret, R.; Boursiquot, J. M.; Merle, M. H.; Cabanis, J. C.; This, P. J. Agric Food Chem. 2000, 48, 5035-5040). In the present paper, we accessed the usefulness of this technology for the analysis of must and wine mixtures. The detection limit of DNA mixtures was first estimated on DNA extracted from leaves: 4% of a foreign DNA can be detected. Analysis of must and wine mixtures (Chardonnay B/Clairette B and Syrah N/Grenache N) was performed on experimental fermentations. DNA was extracted along the fermentation process and analyzed using five microsatellite loci. The 70:30 (v/v) mixtures were successfully analyzed until the end of the fermentation. The applications of these results to commercial purposes are discussed.
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