The Response of Some Morphological and Physiological Traits of Landraces of Savory (Satureja hortensis L.) to Levels of Salinity and Defoliation Stress

Environmental stresses are the most important factor in reducing the yield of agricultural products worldwide. Salinity and defoliation stresses are the most important environmental stresses that affect the properties and production of plants. Salinity stress is also considered as a hyperionic stress and is a major abiotic stress limiting growth and productivity of plants in many areas of the world due to increasing use of poor quality of water for irrigation and soil salinization and defoliation stress is removing leaves from plant or area of land for agricultural purposes that reduces plant fitness. Savory is a medicine herb which its scientific name is Satureja hortensis and is native to the eastern mediterranean and southwestern Asia (Iran). savory is from the Labatiae family, which runs through the months of July to september in Iran. It has soft and rectangular leaves and almost petiolate and narrow and have a lot of essential glandular fibers. Winter savory is Satureja montana and summer savory is Satureja hortensis that are two important species of savory and it has pink to blue-white flowers that attract honey bees. Savory has properties treats nerve pain, increases blood coagulation factors, decreases fat and weight.

To determine the resistance of the savory landraces in this study to salinity and defoliation stresses and planning for breeding programs in the future, a factorial experiment randomized complete design was carried out with three replications in greenhouse conditions in Payame Noor University of Mashhad, in 2017 and 2018. Treatments consisted of four levels of salinity (0, 3, 6 and 9 dS.m-1), three levels of defoliation stress (0, 25 and 50%) and five savory landrace (Kalat, Isfahan, Hamedan, Dargaz, and Mashhad). The traits of this project contained height, number of leaves, number of branches, fresh, dry weight of root, stem and leaf, leaf relative water content, membrane constant coefficient, proline and carbohydrate. Salinity and defoliation stress was applied to the plant after 8-leaf level. Statistical analysis of these data was done using Minitab and MSTAT-C software and then comparison of the meanings by LSD method was done at a significant level of 5%.

The results of this study indicated that defoliation stress has significant effect on all traits of savory measured landraces and the maximum and minimum values of these traits were observed zero and 50 % at defoliation level. So the values of the morphological traits and fresh and dry weight of savory organs were decreased by increasing the salinity levels. Also the content of proline and soluble sugars were increased by salinity stress. According to research of Santa Maria et al. (2001), proline is a low molecular weight protective metabolite that increases resistance and prevents damage from salt stress. Prado et al. (2000) also considered carbohydrate increase as a way to reduce the effects of osmotic and ionic stress and, ultimately, adapt plants to these conditions. According to Greenwich and Mon (1980), due to the salinity stress, the growth of the Sorghum plant is stopped due to low water potential, ionic toxicity and excretion imbalance by salinity, which in our study also reduced the morphological traits by increasing salinity and defoliation stress levels.

According to the results, Kalat and Hamedan landraces were superior to various levels of salinity and defoliation stress for morphological traits and fresh and dry weight of different Satureja organs. The maximum amounts of proline and carbohydrate were observed in Mashhad landrace, Due to these two traits, Mashhad landrace is known as a salt-resistant landrace. The maximum value of membrane constant coefficient was observed in Hamedan landrace. The highest value of leaf relative water content was observed in Kalat landrace.