Improving water use efficiency and root morphology with deficit irrigation in two table grape (Vitis vinifera L.) varieties

Soil water availability is a key factor influencing plant growth and physiological function. This study investigated the physiological responses of two table grape varieties (Emerald Green and Crimson) to four levels of deficit irrigation. Seedlings were grown in pots and subjected to achieve soil field capacity at 90% (CK), 80% (T1), 70% (T2), and 60% (T3), from May 30 to October 20, 2022. Plant water consumption, relative leaf water content, water use efficiency, biomass, plant height, root morphology, Malondialdehyde (MDA) content, and Superoxide Dismutase (SOD) activity were investigated. Results showed that plant height was significant influenced by variety not irrigation level; Root growth and biomass were significant affected by variety, irrigation and interaction between variety and irrigation. Deficit irrigation significantly increased root diameter and root-to-shoot ratio, but decreased total root volume for the same variety. Compared to CK, root diameter increased by 3.35~15.78% and root volume decreased by 23.90~65.44%. Under the same irrigation level, the leaf relative water content in Emerald Green increased by 18.87%, while Crimson peaked at 89.29% under T2. Notably, T2 reduced irrigation water use by 45% while increasing water use efficiency by 70%. In conclusion, maintaining soil field capacity at 70% (T2 treatment) optimized water use efficiency and root development in table grape seedlings while significantly reducing irrigation water consumption by 45%. However, shoot growth was substantially reduced under all deficit treatments relative to fully irrigated controls, and all recommendations are applicable to seedling-stage production under controlled greenhouse conditions pending field validation. Our findings demonstrate that deficit irrigation is a viable strategy for sustainable table grape production in water-limited conditions.