Effect of water deficits on pomegranate tree performance and fruit quality – A review

Abstract

Adaptation to global warming-induced climatological changes, limited water resources and water restrictions for agriculture during drought requires producers to invest in crops matched to the potential future climate, such as drought-tolerant pomegranate trees. For effective application of water saving irrigation management strategies in orchards, knowledge of tree shoot and fruit growth patterns and plant response to water deficits is essential. The review focuses on the effects of water deficits on pomegranate tree physiology, phenology, vegetative growth, fruit growth, yield and fruit and product quality. Mild and severe water deficits in pomegranate trees could decrease stomatal conductance by between 19% to 36% and 53% to 77%, respectively, relative to well-watered trees. Water deficits decreased vegetative growth and fruit growth rate and if applied over several seasons can decrease long term orchard productivity. Mild water deficits during flowering and fruit set can in some cases limit shoot growth without significantly reducing yield. Maximum relative yield was achieved where between 721 and 953 mm evapotranspiration occurred. Relative yield for selected cultivars decreased by 24%, 34% and 45% if seasonal minimum midday stem water potential decreased by −0.5, −1 and −1.8 MPa relative to that of well-watered trees. For selected cultivars the total soluble solids in fruit juice increased as seasonal minimum midday stem water potential decreased. With regard to fruit skin and juice colour and bioactive compounds, deficit irrigation studies produced conflicting results. Differences in pomegranate tree physiological, growth and yield responses to water deficits may be attributed to diverse cultivar drought tolerance, crop load, climatic conditions, irrigation water quality, soil water management practices and the resultant soil water availability. A soil-plant-atmosphere-continuum approach to research could aid in better understanding of the tree response to water deficits and supply fundamental knowledge to formulate appropriate irrigation strategies to achieve optimal water use productivity.