Comparison of Some Morpho-Physiological Characteristics and Fruit Yield of Hybrids of Cucumber (Cucumis sativus)

Introduction Cucumis sativus L. (2n=2x=14) originates from the south of the Himalayan mountains and has at least 3000 years of history of cultivation in India. According to the latest statistics published by the Ministry of Agriculture, about 75% of greenhouse production belongs to greenhouse cucumbers. This plant, with a cultivated area of 7539 ha-1 and a production amounting to 1923865 t year-1, is considered one of the most important vegetable and summer greenhouse products in the country. Cucumber varieties should have characteristics such as high yield, quality of taste, shelf life and resistance to diseases. Based on this, modified cultivars and imported cultivars must pass compatibility tests in order to be able to enter commercial fields. Recent research in Japan shows that by creating suitable conditions for various factors in the greenhouse (light distribution, temperature, humidity, carbon dioxide, irrigation, nutrition and pruning), the yield of greenhouse cucumbers can be up to 40 kg m-2 year-1 year. The difference between different varieties of cucumber is primarily due to characteristics such as the number of fruits per plant, fruit size (fruit length and length-to-diameter ratio) and fruit surface characteristics (the presence of grooves, surface smoothness, and fruit color). The number of cucumbers per plant is one of the most important yield components. The study of 9 varieties of cucumbers in greenhouse conditions showed that the range of changes in the number of cucumbers per plant varied from 19 to 54.3, and Khasib variety had the highest yield with the production of 14.9 kg of fresh weight per square meter.   Material and Methods In order to compare the yield, yield components and some morpho-physiological characteristics of greenhouse cucumber hybrids produced in the country, a research was conducted in 2022 under greenhouse conditions in Varamin city. In this research, 11 greenhouse cucumber hybrids along with 4 regional control cultivars were evaluated in a completely randomized block design with three replications. The initial tillage including plowing, disc and soil disinfection was done through sunning the soil. The width of the seed planting bed was considered to be 70 cm in order to provide the possibility of two-row cultivation. The width of the corridors was considered to be 80 cm in order to provide proper ventilation and access of workers to the bushes for operations and harvest during the period. The drip irrigation system was chosen so that one tape strip could be used for each row of crops. The plant needed fertilizer during the growth period and was determined based on the soil test and provided to the plant through the irrigation system. Fruit yield for different harvests (once every 10 harvests) and total fresh fruit yield based on the total area of the plot (after removing the margins) and traits such as plant height (meters), internode length (cm), leaf length (cm), Leaf width (cm), petiole length (cm), fruit length (cm), fruit diameter (mm), number of fruits per plant and fruit weight per plant (grams) based on the selection of 10 plants per plot was taken. The fruit shape index was obtained from the ratio of the length to the diameter of the fruit. For the experimental hybrids, after harvest fruit color was determined by grouping (light green to green), (green), (green to dark green) and dark green.   Results and Discussion Based on the obtained results, the hybrid (IR4) with a total fresh fruit yield of 11.49 kg m-2 had a significantly higher performance than other hybrids, but there is not a significant difference between this hybrid and the hybrid (IR5) with a fruit weight of 10.61 kg m-2. 10 harvested stages for two hybrids (IR4) and (IR5) constituted 24.6 and 22.9% of the total yield, respectively. The hybrids (IR11) and (IR6) had the longest and shortest fruit length with 16.60 cm and 11.12 cm, respectively. The fruit shape index (the ratio of fruit length to diameter) in hybrid (IR11) had the highest value (6.35). The hybrids (IR4) and (IR5) that produced the highest yields per hectare had the highest number of fruits plant-1 with 108.72 and 84.22 cucumbers plant-1, respectively. The presence of this number of fruits is one of the important factors for producing high yields in these two hybrids, and the number of fruits in the rest of the hybrids is often in the range of 50 to 70 cucumbers per plant. Although in some studies the number of 135 fruits plant-1 is also mentioned for greenhouse cucumbers, but in most cases this number is less than 50. The color of the fruit is also an important quality attribute that is very important in the cucumber market. This trait varies from light green to dark green. Hybrid (IR9) dark green, hybrids (IR2), (IR6), (IR13) (IR15) dark green to green, hybrids (IR1), (IR3), (IR4), (IR5), (IR12) and (IR14) was green and hybrids (IR7), (IR8), (IR10) and (IR11) had light green to green color. The superior performance of two experimental hybrids and the equal performance of 7 other experimental hybrids (out of 11 studied hybrids) compared to the control hybrids can be a good promise for the production of greenhouse cucumber hybrid varieties by domestic companies.