Physiological and Biochemical Responses of Almond (<i>Prunus dulcis</i>) Cultivars to Drought Stress in Semi-Arid Conditions in Iran

Identifying and selecting almond cultivars with drought tolerance traits is crucial for developing more resilient cultivars, especially in regions prone to water scarcity or facing changing climate conditions. In this study, the physiological and biochemical responses of different almond cultivars to water stress were evaluated using a randomized complete block design (RCBD) with three replications at the Agricultural and Natural Resources Research Center of Chaharmahal and Bakhtiari Province, Shahrekord, Iran, during the 2020 and 2021 growing seasons. During each season, the drought stress treatments were applied for four months prior to the collection of leaf tissue and assessment of the physiological and biochemical traits of the treated trees. In general, significant differences were observed for the different effects considered in the fitted model (years, repetitions, cultivars, drought treatments). The relative water content, as well as the chlorophyll a and b contents in the leaves of the evaluated cultivars, significantly decreased with increasing stress intensity. However, the total phenol content and the activities of antioxidant enzymes increased in response to drought stress. There were considerable differences in the studied cultivars’ responses to increasing drought intensity. According to the results, cultivars “Shahrood 8”, “Garnem”, and “Shahrood 12” demonstrated a high antioxidant capacity and the highest resistance, as observed through a smaller reduction in the relative water content under severe drought stress compared with the other cultivars. These results provide valuable insights that contribute to the development of more resilient almond cultivars and rootstocks, particularly in regions susceptible to water scarcity or those experiencing changing climatic conditions.