Monoterpenes are typical aroma components of muscat grape cultivars, providing pleasant floral and fruity aromas to grapes and wines. However, the molecular mechanism of monoterpene biosynthesis between muscat and non-muscat grape remains unclear. Here, the muscat grape cultivar ‘Jumeigui’ and the non-muscat grape cultivar ‘Kyoho’ were chosen as plant materials for a comprehensive transcriptome and metabolite analysis. The gas chromatography–mass spectrometry (GC–MS) analysis demonstrated that a total of 27 and 23 monoterpene compounds were identified and quantified in the ‘Jumeigui’ and ‘Kyoho’ grape, respectively. ‘Jumeigui’ grape accumulated significantly higher concentrations of monoterpenes than ‘Kyoho’ grape. Furthermore, geraniol, linalool, geranic acid, and β-citronellol might be important odorants contributing to the floral character of the ‘Jumeigui’ grape due to the high levels odor activity values (OAVs). Transcriptome analysis demonstrated that the expression profiles of VvDXS, VvGGPPS.SSU1, VvTPS-b/g showed a positive correlation with monoterpene accumulation in grapes. In addition, the expression patterns of the genes involved in jasmonic acid (JA) synthesis and signal were also positively correlated with monoterpene accumulation. All these results will help guide the functional verification of candidate genes related to monoterpene biosynthesis, as well as identify the master transcriptional and hormonal regulators of this pathway in grapes.

Fruit cracking is a phenomenon in which the peel cracks during grape berry development, which seriously affects the yield and quality of the fruit. However, there are few studies on the mining of candidate genes related to berry cracking. In order to better understand the genetic basis of berry cracking, we used the results of previous quantitative trait locus (QTL) mapping, combined with field surveys of berry-cracking types and the berry-cracking rate, to mine candidate berry-cracking genes. The results showed that three identical QTL loci were detected in two years (2019 and 2020); and three candidate genes were annotated in the QTL interval. In mature berries, the expressions of the candidate genes were more abundant in the cracking-susceptible parent (‘Crimson Seedless’) than in the cracking-resistant parent (‘Muscat Hamburg’). Grape berry cracking is a complex trait controlled by multiple genes, mainly including genes encoding cellulose synthase–like protein H1, glucan endo-1,3-beta-glucosidase 12, and brassinosteroid insensitive 1-associated receptor kinase 1. The high expression of the candidate berry-cracking genes may promote the occurrence of berry cracking. This study helps elucidate the genetic mechanism of grape berry cracking.

The aim of this study was to characterize the changes in berry anatomy during the development of grape (Vitis vinifera L., and Vitis vinifera × Vitis labrusca) with different shapes. Paraffin sectioning was used to examine the structural parameters of the cells. The results revealed that, with the development of berries, the transverse and longitudinal diameters of the flesh cells gradually increased, revealing certain regularity. However, the transverse and longitudinal diameters of the epidermal and sub-epidermal cells were different between varieties, reflecting the specificity of the varieties. The growth of the transverse and longitudinal diameters of the berries was found to be completed in the early stage of development. A combination of correlation analysis and size analysis for each cell layer revealed that, due to the small cross-sectional area of the epidermal and sub-epidermal cells, the influence of these cells on the transverse and the longitudinal diameters of the berries would be small. In conclusion, the longitudinal and transverse diameters of the grape berries were mainly determined by the longitudinal and transverse diameters of the flesh cells. The different shapes of the grape berries could mainly be attributed to the different growth rates of the flesh cells in the longitudinal and transverse directions. These different rates of growth led to different lengths and widths of the berry.