Anthocyanin biosynthesis during berry development in corvina grape

Abstract

For the production of a highly qualitative wine, such as “Amarone”, variations in the grape (Corvina) pigment composition are not negligible. The aim of this work was the investigation of the Corvina anthocyanin profile changes during ripening. The experiment took place in 2015, in two vineyards located in Valpolicella (Italy) with different training systems (Guyot and pergola). Micro-meteorological survey, carpological characterization, chemical analysis and transcriptional studies were carried out to clarify the anthocyanin biosynthesis regulation. Air and grape temperatures and global solar radiation inside the canopy were measured during the season. Grape samples were collected at seven stages of berry development from bunches hang until harvest. Berry growth was followed by volume increase. At the beginning of the lag phase, anthocyanin quantification and characterization by spectroscopy and HPLC were carried out. The expression level of structural and regulatory genes of anthocyanin pathway was studied via real-time RT-PCR. At color appearance, the di-substituted anthocyanins prevailed. During ripening, it was observed a progressive increase of tri-substituted, methoxylated, and acylated pigments. A clear correlation among expression of anthocyanin biosynthetic gene, UDPglucose:flavonoid 3-O-glucosyltransferase (UFGT), transcription factors, MybA1 and MybA2, and total anthocyanin content during berry development has been identified. Chalcone synthase, flavonoid 3′-hydroxylase (F3′H) and flavonoid 3′,5′-hydroxylase (F3′5′H) genes of the flavonoid pathway showed high correlation as well. The proportion changes between tri- and di-substituted anthocyanins were associated with an increasing ratio of F3′5′H/F3′H gene transcription during ripening. The AOMT genes were expressed with a maximum at the onset of ripening, coherently with the rapid increase of methoxylated anthocyanin proportion in this stage.