Selection of Six Commercial Iranian Pomegranates (Punica granatum L.) Cultivars for Drought Stress Tolerance Based On Some Leaf Nutrient Elements

Iran has the most diverse and richest gene pool of pomegranate cultivars in the world. Drought is the most common environmental stress and the most important limiting factor of agricultural production in the world and limits production in almost 25% of the world's agricultural lands. One of the most harmful effects of dehydration stress is disruption of the process of absorption and accumulation of nutrients. Among nutrients, potassium is one of the most important cations required by plants, which has been reported to accumulate during osmotic stress. The role of this cation in osmotic regulation and stomatal control has been described. Due to the fact that drought stress is one of the limiting factors for agricultural production, therefore, research on the mechanism of plant resistance to water scarcity is important. Therefore, this study was conducted to investigate the response of six Iranian commercial pomegranate cultivars to drought stress based on the amount of some leaf nutrients.

The executive operations of this research were carried out in the research greenhouse of Lorestan Agricultural and Natural Resources Research Center with a temperature of 25 °C and a relative humidity of 70%. The experiments were performed due to similar climatic conditions of Lorestan and Kermanshah provinces. The plant materials used in this study were annual rooted seedlings of six pomegranate cultivars. This study is a factorial experiment with two factors: 1- Pomegranate cultivar in six levels (RababNeyriz, NaderyBadrood, ShishehcapFerdous, ArdestanyMahvelat, Malase Yazd and ShirinShavar Yazd) and 2- Drought stress in three levels including non-stress drought (80% of field moisture, control), moderate drought (60% of field moisture) and severe drought (40% of field moisture) were screened in a completely randomized design with three replications in the greenhouse. All data obtained from the experiments of this study were statistically analyzed by SAS-9.1 software and the comparison of the mean of the simple effect of the treatments was performed using Duncan's multiple range test. The comparison of the mean interaction of the treatments was performed by SAS and MSTAT-C software using Duncan's multiple range test. Graphs were drawn using Excel software.

The results of this study showed that the amount of nutrients in all studied cultivars was affected by drought stress, but the response to stress was different. The amount of nutrients of iron, zinc, copper, manganese, sodium and phosphorus based on dry weight decreased under drought stress conditions while the concentration of potassium under drought stress increased. Based on the results of this study, Rabab Neyriz and Malase Yazd cultivars had more tolerance to drought stress in terms of nutrient uptake compared to other cultivars, respectively. Highest levels of iron (126.9 mg.g-1), zinc (39.9 mg.g-1), copper (13 mg.g-1), manganese (51.8 mg.g-1) and potassium (2.11% was obtained from Rabab Neyriz cultivar. Therefore, the use of this cultivar in drought stress conditions is recommended. Among the studied cultivars, Naderi Badroud and Ardestani Mehvalat had the highest sensitivity to drought stress and Shirin Shahvar Yazd and Shishecap Ferdows cultivars showed moderate resistance in this regard.

Based on the results of this study, it showed that Rabab Neyriz and Malase Yazd cultivars have high tolerance to drought stress and are also able to show a better response to nutrient uptake under drought stress conditions. Between these two cultivars, Rabab Neyriz cultivar had higher absorption of iron, zinc, copper, manganese and potassium and was considered the superior cultivar in this regard.