## 1 Introduction  
The grapevine (_Vitis vinifera_) is a major fruit crop of high economic importance related to a range of valuable products, including table fruits and wines, worldwide. In Europe alone, wine production exceeds an annual revenue of more than 30 billion \(\epsilon\)[1]. Grape yield and quality traits, including color, flavor, and aroma, are differentially controlled by biotic and abiotic factors throughout the grapevine developmental and processing stages [2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14]. _Vitis_ microbiome is a dynamic biotic factor, receiving great attention due to is inherent link with grapevine productivity, plant health, and product quality traits [10, 13]. The dynamic nature of the _Vitis_ microbiome has been largely ignored, and our current knowledge is limited to selected microbes, i.e.,pathogens [15] or single-point studies of metagenomes prior to fermentation [16; 17]. However, our understanding of how grapevine cultivars and genotypes impact the _Vitis_ associated microbiome in various tissues throughout the cultivation period remains scant [5; 17; 18; 19; 20; 21; 22; 23; 24; 25]. The most widely studied _Vitis_-associated microbes are known pathogens and fermentative yeasts. Those include bacteria and fungi such as _Agrobacteriumrium_ spp. [26], _Xylella fastidiosa_[27], _Xylophilus ampelinus_[21], _Botrytis cinerea_[28], _Erysiphe reactor_[29], and _Plasmopara viticola_[30], causing crown gall, [PERSON]'s disease, blight, gray mold, powdery mildew, and downy mildew, respectively. Among fermentative yeasts (either _Saccharomyces_ or non-_Saccharomyces_ species), _S. cerevisiae_ predominates in must fermentation [31; 32; 33]. Based on the knowledge derived from such studies, technologies have been developed for controlling _Vitis_ pathogens with biological antagonists, improving soil fertility with rhizobial inocula, and improving the wine fermentation process and quality traits with biological commercial products. Nevertheless, _Vitis_-associated microbes reflect direct and indirect relationships with their host and environment [5; 6; 10; 13; 17; 23; 34; 35; 36; 37; 38; 39; 40]. In a fundamental study, [PERSON] et al., 2014 [4] reported that _Vitis_ microbiomes present strong biogeographic regionalization, indicating that local environment shapes distinct microbial consortia, comprising _Vitis_ microbial _terroir_. Further in-depth analysis implied that the host cultivar might also have an additional controlling effect on _Vitis_ microbial communities across different environments. Thus, apart from the environment, the effect of _Vitis_ genotype on the composition of the hosted microbiome needs to be thoroughly investigated. Additionally, the nature of genotype interaction with tissue and developmental stage on microbiome composition is largely unknown. A recent metagenomic study revealed that the host genotype may influence _Vitis_ associated bacteria in the same farming system and vineyard [17]. This exciting new evidence leads to three key questions:(a) Does the host genotype influence the structure of associated fungal communities as well? (b) Does developmental stage and tissue type affect the composition of microbial communities? Lastly,(c) is there a common core microbiome linked to all _Vitis_ cultivars? Considering the recent view of individual plants as holobionts, where hosted microorganisms are involved in major plant functions such as nutrition and resistance to biotic and abiotic stresses [41], the composition and organization of the microbial community could be a major determinant when selecting a grapevine cultivar. However, the detailed microbial colonization process of grapevine is still poorly understood [42]. Thus, the aim of this study was to comprehensively characterize the role of _Vitis_ cultivar genotype on the structure of the associated microbiome, targeting different epiphytic sections and developmental stages.