عنوان مقاله [English]
Introduction: Varieties of melons have long been the most important crops in Iran and have a special place in Iran's agricultural economy which is the third major producers in the world. Different types of melons belong to various botanical groups of Cucumis melo. Salinity stress is one of the limiting factors in the production of crops. Majority lands in Iran have arid and semi-arid conditions. The characteristics of these regions are high evaporation and low rainfall, which causes the accumulation of different salts in the surface layer of the earth. Salinity is one of the most important issues in the world, and millions of tons of salt are come annually from irrigation water into agricultural land. Therefore, many plants are encountered to saline soils. Grafting is developing as a new and effective way to increase the tolerance of plants to salinity in advanced countries. Several reports indicate that the rootstock type has a significant role in the resistance of the scion to environmental stresses. In the present study, salinity tolerance of two Iranian melon accessions (‘Garmak’ and ‘Samsouri’) were investigated based on eco-physiological traits, on three commercial rootstocks and a local variety of cucurbit, as well as comparing them with non-grafting plant of ‘Garmak’ and ‘Samsouri’,.
Materials and Methods: This experiment was conducted as factorial in a completely randomized design with three factors including salinity stress (in three levels) and four rootstocks and two scions with three replications in greenhouse and field of the faculty of agriculture, Vali-e-Asr University of Rafsanjan, Iran. In this study, two melon accessions (‘Garmak’ and ‘Samsouri’) were grafted on commercial hybrids rootstocks (‘Ferro’, ‘Shintozwa’ and ‘Ergo’) and a local variety of bottle gourd and subjected to salinity treatments (0, 20 and 40 mM levels of sodium chloride) in the field. One month after adaptation of grafted plants, grafted and non-grafted plants were transferred to the field and salinity treatment (sodium chloride) was applied one week after planting in the field. The evaluated traits at the end of the experiment were: photosynthetic parameters (total chlorophyll, total carotenoids, photosynthetic efficiency index), relative water content, vascular pressure potential, proline and soluble sugars.
Results and Discussion: The results showed that in salinity treatments, grafted plants were superior to non-grafted plants in studied traits. Differences were also observed between the tested rootstocks, so that the ‘Ergo’ hybrid was weaker in many features than other rootstocks and even non-grafted plants. The results showed that salinity increased the amount of proline and carotenoids in the leaf, which was lower in grafted than non-grafted plants. With increasing salinity, the pressure of vascular pressure decreased. This amount was lower in non-grafted than in plants grafted on ‘Ferro’ and ‘bottle gourd’. Also, the total chlorophyll content and relative water content of leaf decreased, which this reduction was higher in non-grafted plants. Among the traits mentioned, the best studied rootstocks were ‘Ferro’ and ‘Shintozwa’ that were better than other rootstocks as well as non-grafted plants. By increasing salinity, the soluble sugars of grafted plants on ‘Ferro’ and ‘bottle gourd’ decreased, but in grafted plants on ‘Shintozwa’ hybrid, increased salinity increased the soluble sugars content.
Conclusions The results of this study showed that salinity stress significantly reduced the relative water content of leaves, photosynthetic pigments and carotenoids. Salinity also increased the potency of vascular pressure potential and proline concentration. Compared to non-grafted plants, the negative effects of salinity stress on non-grafted plants were more prominent than grafted plants. Also, the amount of photosynthetic parameters in grafted plants decreased less than non-grafted plants. Comparing the two evaluated accessions, ‘Samsouri’ was more appropriate than stress conditions. Compared to non-grafted and grafted plants in non-stress conditions, the best rootstock was ‘Ferro’, which showed the best result for all traits except for proline content in both ‘Samsouri’ and ‘Garmak’. At a salinity level of 40 mM, the ‘Ferro’ and ‘Shintozwa’ were superior to other rootstocks, which showed satisfactory results in most traits. Also, due to the poor reaction of the grafted plants on the bottle gourd rootstock under salt stress conditions, it seems that this rootstock probably due to low compatibility is not a suitable rootstock for two evaluated accessions in the present study. Based on the findings of the present study, ‘Ferrero’ and Shintozwa’ in combination with ‘Samsouri’ and ‘Garmak’ showed more tolerance to salinity.