Evaluation of Salinity Tolerance of Cuttings in some Wild Genotypes, Local and Commercial Cultivars of Pomegranate in Greenhouse Conditions

Salt stress is one of the most important factors limiting the growth, development and the yield of plants that cause structural changes in important plant organs such as stems, roots, leaves and petioles. In salinity conditions, the pomegranate tree cannot produce an economic product. Therefore, identification and use of selected pomegranate cultivars tolerant to salinity stress are necessary for breeding programs, introducing better cultivars and developing the pomegranate industry. Morphological and physicochemical changes can be used as indicators for selecting tolerant cultivars.

This study was conducted in 2019 in a factorial design based on a completely randomized block design in four replications in the laboratory of the department of horticultural sciences at Gorgan University of Agricultural Sciences and Natural Resources. The first factor was pomegranate genotypes in 15 levels, including four wild genotypes (Vahshi Inchehbrun, Vahshi Aliabad and Vahshi Kordkoi from Golestan province, and Miankaleh from Mazandaran province), eight local genotypes (Qand and Torsh Galoogah, Shirin, Torsh, and Gol Anar Behshahr, Fereshteh qermez Sari, Shirin and Torsh Shivand of Khuzestan), two commercial export genotypes (Yosefkhani and Malas momtaz Saveh) and one foreign genotype (Wonderful) and the second factor was the salinity at three levels including control, 2.5 and 6.4 grams per liter of sodium chloride (EC 1.4, 4 and 8 dS/m, respectively). After rooting of the cuttings and growing the new pot plants, salinity stress was applied for 10 weeks. Then, the morphological, physicochemical and phytochemical traits were measured.

The results showed that after applying salinity stress in all genotypes and cultivars, morphological and physicochemical traits such as stem length, stem diameter, the number of branches, the total number of leaves, root length, root diameter, leaf surface and leaf fresh weight, leaf dry weight, the relative water content of leaf, chlorophyll, total phenol and anthocyanin decreased in comparison with the control. Some of the other physicochemical and phytochemical traits such as electrolyte leakage, the percentage of abscised leaves and the percentage of necrotic leaves, cell membrane damage, salinity damage index and proline increased in comparison with the control. Also, the responses of genotypes were different in terms of tolerance to salinity stress and growth traits. Some of the cultivars were introduced as tolerant cultivars, some as semi-tolerant and some others as sensitive. With increasing the salinity stress, the amount of morphological, physicochemical and phytochemical traits changed significantly in sensitive cultivars. Moreover, the results of the analysis of variance showed that the effect of salinity on all measured traits was significant except the root dry weight.

Based on the obtained results, and after ranking and standardization, the Wonderful cultivar was recognized as the most tolerant cultivar. It was able to tolerate the salinity of 6.4 grams per liter of sodium chloride (8 dS/m) well; followed by Fereshteh qermez and Malas Saveh. Torsh Galoogah, Torsh Shivand, Vahshi Inchehbrun, Shirin Shivand, Qand Galoogah, and Vahshi Miankaleh were identified as semi-tolerant cultivars and Vahshi Aliabad, Torsh Behshahr, Gol Anar behshahr, Vahshi Kordkoy and Shirin Behshahr were identified as sensitive cultivars to salt stress.