Leaf removal and deficit irrigation have diverse outcomes on composition and gene expression during berry development of Vitis vinifera L. cultivar Xinomavro

The quality characteristics of a certain grapevine cultivar are determined by the combinatorial action of the genotype and environmental factors, such as soil, landscape and climate. Another critical parameter is the viticultural techniques utilised to improve grape berry quality. The influence of two viticultural practices, deficit irrigation and leaf removal, on the Greek Vitis vinifera L. cultivar ‘Xinomavro’ was investigated during the 2019 and 2020 vintages. Physiology measurements and berry sampling were performed at three phenological stages (green berry, veraison and harvest). The expression of specific genes known to control grape colour, aroma and flavour was studied in conjunction with berry growth and composition. All the parameters contributing to final yield, such as berry size, cluster weight and yield/vine, were reduced in non-irrigated and defoliated vines compared to their control (irrigated and non-defoliated) vines. Both treatments showed a significant increase in anthocyanin level, whereas total phenols increased in the deficit irrigation treatment only. Water deficit had no effect on total soluble solids, whereas leaf removal resulted in significantly increased levels compared to the controls. The expression profile of the genes examined was altered during ripening. Although both water deficit and defoliation positively influenced gene expression, there were several diverse responses among the phenological stages that depended on the vintage.