Effect of Salinity Stress on Yield and Yield Components of Three Iranian Cantaloupe Masses

Cucumis melo L. is one of the most important horticultural products in Iran. According to some reports from the third millennium BC, it has been under cultivation in. High nutritional value and high vitamin A, vitamin C, calcium, potassium, magnesium and iron have made it to be a valuable fruit. According to the environmental conditions and cultivar, melon flowering began 30-60 days after planting and 30-70 days after pollination, the product can be harvested. Immature melon is tasteless and towards maturity, its sweetness increases. From the economic point of view, the minimum acceptable sweetness of melon's cultivars is 9% in terms of the total amount of fruit-soluble solids, but according to the vendors, this number should be 11% or more. The arid and semi-arid regions of the world are the main habitat for such products as melon and salinity stress as an integral part of these areas is an important factor for decreasing yield. The effect of salinity stress in melon's reproductive stage is somewhat more complex than other products, because some reports indicated a significant decrease in yield, number of fruit and weight of melon fruits in salinities greater than 2 dS m-1 and even some researchers determine the threshold of tolerance of 1 dS m-1. The present study was conducted to investigate the effect of two salinity treatments on yield and yield components of three melon cultivars in Varamin province. This research was carried out in 2013 using split plot design in a randomized complete block design with three replications in Varamin Agricultural Center located in 45 km Southeast East of Tehran (35 ° 35 ', 19', 51 ', 39') 1000 meters above sea level. Prior to the experiment, the first step was to prepare the soil including deep plowing and disc. The main plots consisted of irrigation water salinity treatments at 8 dS m-1 (prepared from the Ishraq area) and 2 dS m-1 (prepared from the Khaveh station). The subplots consisted of 3 Cantaloupe masses, including Semsoori Varamin, Green Tile of Mashhad and Magasie Neishabur. The soil of the place-tested sandy loam and the amounts of organic matter (in percent), acidity and salinity (in dS m-1) were 0.95, 7.5 and 2.1 respectively. Based on the soil test, 100 kg ha-1 phosphorus (triple superphosphate) and 150 kg ha-1 potassium (as potassium sulfate) and 150 kg ha-1 nitrogen fertilizer (urea before and after flowering) were added to the ground the experiment. The cultivation date was selected May 5th. The length and diameter of the flesh with the ruler and the percentage of fruit-soluble solids were measured using a refractometer based on 10 fruits, and then the mean of the obtained numbers was taken as the final value. Before harvest, the average number of fruits per plant and average fruit weight were measured and recorded based on the performance of sub plots and the middle lines of each plot. All soil and vegetation tests were carried out in the laboratory of the Soil and Water Research Department of Varamin Agricultural Research Center. Statistical analysis was performed using SAS software and the meanings were compared with Duncan's method (5%). The effect of interaction of salinity and genotype on the length of the fruit (at 1% level) and on the traits of seed cavity thickness, percentage of soluble solids, fruit meal diameter, fruit weight and fresh yield (at 5% level) were statistically significant. In salinity 8 dS m-1 compared to 2 dS m-1, the fresh yield of Semsuri Varamin, Green Tile of Mashhad and Magase Neishabur decreased by 32.7, 45.6 and 80%, respectively. Salinity stress can increase the percentage of non-marketable fruits by reducing the weight of fruits, and it is reported in salinity of 8 dS m-1, which is a 56% decrease in marketable yield. The highest reduction in fruit weight and number of fruits per plant were related to the two mass of Magase Neishabur (average weight 540 g) and Green Tile of Mashhad (average number of 1.23 fruit per plant), respectively. Similarly, in a research with a salinity increase of 2.41 dS m-1 to 12.6 dS m-1, yields dropped from 37 t ha-1 to 28 t ha-1, mainly due to the reduction in the number of fruits. The length of fruits in three populations of Semsuri Varamin, Green Tile of Mashhad and Magase Neishabur in the salinity of 8 dS m-1 compared to 2 dS m-1 decreased by 25, 30 and 45%, respectively. Increasing salinity from 3 to 5 dS m-1 caused a significant decrease in fruit length in products such as cucumber (equivalent to 25%). Increasing the percentage of fruit solids in salinity of 8 dS m-1compared to 2 dS m-1 treatment, was 5.8, 1.75 and 1.5 times, respectively, in the Magase Neishabur, Green Tile of Mashhad and Semsuri masses. In a study in which the effect of different treatments on salinity was investigated on the percentage of soluble fruit solids, increasing salinity from 2 to 8 dS m-1 increased the percentage of soluble solids from 7.6 to 10.5 percent.