Study Identifies Drought Genes in Italia Grapes

A new study of the table grape cultivar Italia has identified a set of genes that respond to drought in ways that could help breeders and growers better understand how vines cope with water shortages, a growing concern in Mediterranean viticulture as heat and dry spells become more common.

The research, published April 30 in Horticulture, Environment, and Biotechnology, followed potted Italia vines in a greenhouse at the University of Bari in southern Italy for 37 days without irrigation. Scientists measured leaf water potential, transpiration, photosynthesis and stomatal conductance while also tracking the activity of six genes previously flagged in transcriptomic work but not yet validated one by one.

The vines were grown under controlled conditions from September to October 2013. One group was kept at field capacity, while another had irrigation stopped. By the end of the trial, soil water potential in the drought-treated plants had fallen to -200 kPa from about -14 kPa in the control group. Leaf water potential also dropped sharply after day 30. At the same time, transpiration and net assimilation declined, and stomatal conductance fell to zero in some stressed plants by day 37.

The gene work focused on VvPP2C4 and VvPP2C8, which are tied to abscisic acid, or ABA, signaling; VvGolS1 and VvGolS2, which are linked to osmoprotection; and VvHSP18 and VvRD26, which help cells withstand stress. The researchers found that VvPP2C4 rose significantly after 37 days of drought, while VvPP2C8 did not change significantly. VvGolS2 increased at day 37, VvHSP18 rose late in the trial, and VvRD26 showed the strongest response, increasing from day 14 and reaching about 80-fold higher expression by day 37 compared with the control plants. VvGolS1 did not show significant variation.

The authors said the pattern points to a coordinated drought response centered on ABA signaling and osmotic protection. They also reported correlations between gene activity and plant physiology. VvRD26 was strongly negatively correlated with photosynthesis, transpiration and stomatal conductance, while VvPP2C4 also showed negative correlations with photosynthesis and transpiration.

The study is notable because it validates candidate drought-response genes in Italia grapes under controlled stress rather than relying only on broad transcriptome data. That matters for breeding programs seeking varieties that can maintain productivity with less water and for irrigation strategies in regions where water scarcity is already affecting grape quality and yield.

Italy remains one of the world’s major table grape exporters, with Puglia accounting for a large share of national production. The authors said that understanding how Italia vines respond at both the physiological and molecular levels could support efforts to sustain that sector as climate pressure increases across southern Europe.