Effect of Salt Stress on Morphological Traits of Lettuce Genotypes (Lactuca Sativa L.)

The recognition of salt tolerant plants is important as a result ofincreasing saline lands in Iran and world. Cultivation of plants in hydroponic environment is a reliable and economical method in order to select the salt tolerant plant. Salt stress can effect on plant growth and development by ion toxicity, ionic disturb the balance and osmotic potential. Lettuce is one of the most important vegetable crops. This plant is one of the most important leafy vegetables which is used for salad and fresh marketing, also some types of this vegetable is used in baked type. The aim of this study was to investigate the genetic diversity of lettuce genotypes undersalt stress in the hydroponic system.
To assess response of lettuce seedlings to salt stress, a factorial experiment was conducted in a completely randomized design with three replications at Biotechnology Research Institute for hydroponic cultivation of Zabol. In this experiment, the effects of three salinity levels (0, 2 and 4 dS/m) on morphological characteristics of 15 lettuce genotypes were evaluated. The seeds were sterilized for ten seconds in ethanol 96% and then 15% sodium hypochlorite solution for 50 seconds, then rinsed several times with distilled water, then disinfected seeds were cultured in plastic pots containing coco peat and perlite. After …days plants were transferred to hydroponic system containing Hoagland solution. Collected data were analyzed and means comparisons were made using LSD by SAS software.
The results showed that salinity has a significant effect on seedling growth of lettuce genotypes (p≤0.01). significant difference between salinity levels and genotype were observed for all traits. Interaction of genotype and salinity for all the traits except root length, plant length and leaf were significant at 1%. Based on the results, the greatest root length was belong to Esfahan Varzaneh leafy lettuce and Romaine lettuce long green Teresa genotype, respectivly. Increasing salinity led to significant reduction (p≤0.01) in the plant length lettuce in all genotypes. Root and plant fresh weight lettuce genotypes were significantly (p≤0.01) influenced by different levels of salinity. The greatest amount in root and plant fresh weight lettuce genotypes were obtained in the control treatment and the lowest amount at the level of 4 dS/m. Root and plant dry weight lettuce genotypes were significantly (p≤0.01) influenced by the salinity. Root and plant dry weight decreased with increasing salinity. So that the greatest amount of root and plant dry weight lettuce genotypes were obtained in control treatment and the lowest amount at the level of 4 dS/m.. The results showed that root and plant length ,root fresh and dry weight, plant fresh and dry weight and leaf length and width reduced with increasing salinity. The clustering pattern the genotypes were grouped into 3 clusters based on their charachters at 4 dS/m salinity. The first cluster were placed in salt tolerant groups, while the other genotypes were clustered into moderately tolerant cluster. Romaine lettuce long green Teresa genotype was placed in salt-tolerant group and Lettuce Everest, Lettuce May Queen, Curly endive hair angel, Cabbage Milan Aubervilliers and Romaine lettuce long blonde Galaica were placed in salt-sensitive group.