Evaluation of some physiological and morphological characteristics of three genotypes of the ornamental pomegranate (Punica granatum L.) under salt stress

Pomegranate (Punica granatum L.), from the family Punicaceae, is a popular fruit of tropical and subtropical regions that is native to the area stretching from Iran to the Himalayas in northern India. Pomegranate has been widely cultivated in arid and semi-arid regions of Iran, which these areas are frequently affected by high salinity. The present study was therefore, carried out with the objective to identify and introduce the most-tolerant Iranian genotypes of ornamental pomegranate to different salinity levels of irrigation water.

A pot experiment was conducted during a six-month period in order to evaluate and compare the salinity tolerance of three Iranian ornamental genotypes of pomegranate during 2017-2018. The experiment was arranged in factorial based on the completely randomized design with two factors included water salinity in 5 levels of 1, 3, 5, 7 and 9 dSm-1 and three ornamental pomegranate genotypes (‘Golnar Saravan’, ‘Golnar Shahdad’ and ‘Golnar saveh’) in 4 replications. The properties concerned during the experiment were vegetative growth, the fallen, chlorosis and green of leaves. At the end of the experiment, the vegetative yield and fresh and dry weight of leaves and shoots, ion leakage, relative water content and chlorophyll index were also measured. In addition, leaves were analyzed for elements such as Na+, K+, Cl– and Na/K ratio.

Results showed that with increasing of salinity levels in all three investigated genotypes, growth characteristics, significantly decreased, ion leakage, the relative water content of leaves and chlorophyll index significantly increased. Also with increasing of salinity levels Na+, Cl- and Na+/Cl- significantly increased. In all studied genotypes, plant height and leaf area decreased from salinity level of 5 and 7 dS.m-1 respectively. Increasing in leaf necrosis, and decreasing in percentage of green leaves and also relative water content in ‘Golnar Sarvestan’ were observed from salinity level of 5 dS.m-1and from salinity level of 7 dS.m-1 in ‘Golnar Shahdad’ and ‘Gonar Saveh’. Leaves falldown in ‘Gonar Saveh’ and ‘Golnar Sarvestan’ were increased in salinity level of 7 dS.m-1 and in ‘Golnar Shahdad’ in 5 dS.m-1 salinity level. In two genotypes (‘Golnar Sarvestan’and ‘Golnar Shahdad’) the ion leakage increased in 7 dS.m-1 salinity level and in ‘Gonar Saveh’ in salinity level of 5 dS.m-1. In higher salinity levels (7 and 9 dS.m-1) Na+, Cl- and Na+/Cl- uptake were significantly decreased in ‘Golnar Sarvestan’and ‘Golnar Shahdad’ in compared to ‘Golnar Sarvestan’.

Generally among all studied genotypes, ‘Golnar Shahdad’ has been showed the maximum growth characteristics, and the lowest appearance injury, accumulation of Na+, Cl- in higher levels of salinity. So it seems that this genotype is the most tolerant of the salinity.