Pink berry grape (Vitis vinifera L.) characterization: Reflectance spectroscopy, HPLC and molecular markers

Georgian Grapevine Cultivars: Ancient Biodiversity for Future Viticulture

Grapevine (Vitis vinifera) is one of the most widely cultivated plant species of agricultural interest, and is extensively appreciated for its fruits and the wines made from its fruits. Considering the high socio-economic impact of the wine sector all over the world, in recent years, there has been an increase in work aiming to investigate the biodiversity of grapevine germplasm available for breeding programs. Various studies have shed light on the genetic diversity characterizing the germplasm from the cradle of V. vinifera domestication in Georgia (South Caucasus). Georgian germplasm is placed in a distinct cluster from the European one and possesses a rich diversity for many different traits, including eno-carpological and phenological traits; resistance to pathogens, such as oomycetes and phytoplasmas; resistance to abiotic stresses, such as sunburn. The aim of this review is to assess the potential of Georgian cultivars as a source of useful traits for breeding programs. The unique genetic and phenotypic aspects of Georgian germplasm were unraveled, to better understand the diversity and quality of the genetic resources available to viticulturists, as valuable resources for the coming climate change scenario.

Iron deficiency stimulates anthocyanin accumulation in grapevine apical leaves

Iron chlorosis is a diffuse disorder affecting Mediterranean vineyards. Beside the commonly described symptom of chlorophyll decrease, an apex reddening was recently observed. Secondary metabolites, such as anthocyanins, are often synthetized to cope with stresses in plants. The present work aimed to evaluate grapevine responses to iron deficiency, in terms of anthocyanin metabolism (reflectance spectrum, total anthocyanin content, HPLC profile and gene expression) in apical leaves of Cabernet sauvignon and Sangiovese grown in hydroponic conditions. Iron supply interruption produced after one month an increasing of anthocyanin content associated to a more stable profile in both cultivars. In Cabernet sauvignon, the higher red pigment accumulation was associated to a lower intensity of chlorotic symptoms, while in Sangiovese, despite the activation of the metabolism, the lower anthocyanin accumulation was associated to a stronger decrease in chlorophyll concentration. Gene expression data showed a significant increase of anthocyanin biosynthesis. The effects on the expression of structural and transcription factor genes of phenylpropanoid pathway were cultivar dependent. F3H, F3'H, F3'5'H and LDOX genes, in Cabernet sauvignon, and AOMT1 and AOMT genes, in Sangiovese, were positively affected by the treatment in response to iron deficiency. All data support the hypothesis of an anthocyanin biosynthesis stimulation rather than a decreased degradation of them due to iron chlorosis.

Spontaneous variation regarding grape berry skin color: A comprehensive study of berry development by means of biochemical and molecular markers

Understanding grape berry development and the metabolism of different classes of compounds responsible for traits like berry's color is imperative to control and improve quality aspects of grapes. A colorimetric, biochemical and molecular characterization allowed the comprehensive description of the pigment-related characteristics of nine berry skin color somatic variants, belonging to four different varieties. Although the observed berry skin color variability was not fully explained by MybA locus, the phenolic profiles allowed inferring about specific interferences among the biosynthetic pathways. Data were consistent concerning that grapes showing cyanidin-3-O-glucoside as the major anthocyanin and flavonols with two substituent groups in the lateral B-ring are generally originated by a white ancestor. After retro-mutation, these grapes seem to keep the dysfunction on flavonoid hydroxylases enzymes, which negatively affect the synthesis of both flavonols and anthocyanins with three substituent groups in the lateral B-ring. Overall, the obtained results indicate that the color differences observed between somatic variants are not solely the result of the total amount of compounds synthesized, but rather reflect a different dynamics of the phenolic pathway among the different color variants of the same variety.

CHEMICAL COMPOUNDS

Gallic acid (PubChem CID: 370); Caftaric acid (PubChem CID: 6,440,397); Catechin (PubChem CID: 73,160); Epigallocatechin gallate (PubChem CID: 65,064); Quercetin-3-O-galactoside (PubChem CID: 5,281,643); Quercetin-3-O-glucoside (PubChem CID: 25,203,368); Malvidin-3-O-glucoside (PubChem CID: 443,652); Peonidin-3-O-p-coumaroylglucoside (PubChem CID: 44,256,849); Malvidin-3-O-p-coumaroylglucoside (PubChem CID: 44,256,988); Resveratrol-3-O-glucoside (PubChem CID: 25,579,167).