Multicultivar and multivariate study of the natural variation for grapevine bunch compactness

Abstract

Background and Aims Grapevine bunch compactness is an important trait with impact on fruit quality, mainly affecting the susceptibility to bunch rot. Many and different variables have been reported to have a significant influence on the variation of bunch compactness in particular cultivars, but little is known about the role of such variables in a wider framework. The aim of this work was to identify and weight the features responsible for the natural variation in bunch compactness in a large and diverse grapevine collection. Methods and Results Different statistical tests were sequentially applied to select the determining variables most influencing bunch compactness. Significant and low correlation was obtained for most of the variables studied for three consecutive seasons, confirming the multifactorial nature of this trait. Multivariate analyses indicated that there are three groups of variables with a significant influence on bunch compactness. Two groups, represented by the total number of berries per bunch and by the length of the first ramification of the bunch, are major factors responsible for the trait variation, whereas berry dimensions have a secondary role. Conclusions Bunch compactness is defined by the difference between its morphological (apparent) volume and its actual (solid) volume. The results showed that the actual volume is mainly determined by the total number of berries, whereas the morphological volume also depends on its spatial arrangement, determined by the architecture of the rachis. Significance of the Study This is the first multiyear study of bunch compactness at a multicultivar level, and it has allowed the selection and weighting of the main variables affecting the trait. These variables are suitable targets to study the underlying genetics of the trait.

A multivariate approach for the ampelographic discrimination of grapevine (Vitis vinifera) cultivars: application to local Syrian genetic resources

“…1). As previously reported in different intergenotypic works (Leão et al 2010(Leão et al , 2011Khadivi-Khub et al 2014;Tello et al 2015), the highest absolute correlations were obtained between traits of the same category (i.e. leaf, cluster and berry traits, Table 1).…”

“…Interestingly, seed number (BE_SB) did not correlate significantly with berry dimension variables (BE_We, BE_Wi) or its value of significant correlation was low (BE_Le). It is generally accepted that berry dimensions are directly affected by seed number at a intragenotypic level (Walker et al 2005), but it is not that obvious at an intergenotypic level Tello et al 2015). In this regard, Doligez et al (2013) have indicated the lack of colocalization between QTLs for berry and seed traits, suggesting that the genetic control of both traits may be partly dissociated.…”

“…A Principal Component Analysis (PCA) was performed to identify the underlying relationships between the 27 quantitative traits evaluated in this work (Table 1), retaining those PCs whose eigenvalues were higher than 1. Then, a stepwise linear discriminant analysis (stepwise-LDA) was conducted as previously indicated (Tello et al 2015) to select a reduced set of variables with a high capability to discriminate the different grapevine cultivars used in this study. The predictive capability of the canonical functions released was assessed both by direct and by leave one-out cross-validation.…”

Application of 2D and 3D image technologies to characterise morphological attributes of grapevine clusters

“…On the other hand, cluster selection is becoming a common practice at some wineries for selecting high quality fruits to produce premium wines . In this light, winemakers usually reject highly compact clusters, which are considered of lower quality . Cluster size, shape and compactness are routinely evaluated by visual methods, like those proposed by the International Organisation of Vine and Wine (O.I.V.)…”

“…Each ramification comprises a highly variable number of berries, whose size and shape also vary widely . This singular structure means two different volumes can be considered in the cluster: the actual (or solid) and the morphological (or apparent) one, and cluster compactness is determined by the difference between them . The actual volume of the cluster is mainly composed of the volume of the berries (the volume of the rachis – or stem – is insignificant), whereas the morphological one is also defined by the way that this solid volume is arranged three‐dimensionally .…”