Drought preconditioning improves freezing tolerance in drought-tolerant and -intolerant grape cultivars

Plants preserve previous abiotic stress memory that may help achieving tolerance to subsequent stresses. We tested whether drought priming could alleviate freezing injury in two grape cultivars, namely ʻAsgariʼ (drought-tolerant) and ʻYaghutiʼ (drought-sensitive). To study the factors involved in drought acclimation process and their role in inducing freezing tolerance, irrigation was withheld for 20 days and carbohydrate and proline concentrations were measured regularly during this time. The results indicated that withholding irrigation decreased the starch, fructose and total soluble carbohydrate (TSC) concentrations. Rewatering increased starch, fructose and TSC concentrations to values exhibited by the plants under water stress conditions. The results also indicated how irrigation regimes strengthened over time. At the end of the study, negative and positive correlation coefficient between starch and proline concentrations and shoot LT50 (lethal temperature at which 50% of the total ion leakage occurs) were found, respectively. Root LT50 also followed the same correlation response as shoot LT50. ʻAsgariʼ water-stressed plants performed better under drought by maintaining leaf water status and chlorophyll index, and less damage to photochemical efficiency as compared to ʻYaghutiʼ. Drought stress affected positively the cold hardiness, with higher freezing tolerance and less damage to shoot and root tissues.