Extended Abstract   

  Introduction and Objective:

  Alfalfa is the most important leguminous forage, which plays a very important role in providing fodder needed for the production of human protein and dairy products. This plant has high nutritional value and its adaptability to different conditions is high. Alfalfa is recommended for sustainable agriculture because it has a deep root system and because it is perennial, it can prevent soil erosion. Alfalfa is an excellent source for biological fixation of air nitrogen. Researchers believe that 65% of the total nitrogen used in agriculture is through biological nitrogen fixation. In terms of the quality of fodder and the optimal amount of energy from plants, it is very palatable and effective in the growth of livestock. In addition to protein, this plant is rich in vitamins, especially A, C, E, K and mineral compounds such as calcium. Distribution of types of annual alfalfa at the global level, especially in arid and semi-arid regions, shows their resistance to water shortage and drought conditions. Alfalfa can be used as successful plants to prevent desertification and expansion of deserts. Among annual alfalfas, there are species that are able to adapt to 80 to 100 mm of winter rain for improvement and development in dry areas and desert pastures. However, most of Iran is suffering from water shortage,one of the limitations of breeding for drought stress is the lack of resistance sources among crop genotypes. For this purpose, evaluation of wild genotypes can be an important step in this direction.

  Results:The results showed that drought stress have negative effect on evaluated traits. The differences between all evaluated genotypes were significant in 1% probability level revealed the existence of genetic diversity between genotypes that can be used for selection of drought tolerant genotypes in subsequent study. Also, the interaction effect of genotype in stress conditions for most traits shows that the amount of changes of different genotypes in different moisture conditions was not the same for most of the traits and genotypes. The results of heritability calculation for the studied traits showed that all traits showed high general heritability. The highest heritability for leaf dry weight trait (92.96 under full irrigation conditions and 91.77 under severe stress conditions) and the lowest heritability for internode number trait (71.83 under full irrigation conditions and 66.93 under severe stress conditions) was observed. The highest coefficient of variation related to the trait number of branches per plant (22.49) and the lowest was observed for the trait dry weight of leaves (8.86). In this study Kermanshah130 and Azarbayjan175 genotypes were the most tolerate genotype which had the lowest decrease for dry leaf weight, dry stem weight, stem number, plant height, leaf number and internode length. 

  Material and Methods: 

  This research was conducted on perennial alfalfa genotypes (one variety) and one year alfalfa (nine samples) (Table 1) in factorial form (the first factor of alfalfa genotypes and the second factor of stress) with three replications and in the form of a block design. Samples of alfalfa evaluated in normal and severe stress conditions in research green house in the greenhouse of Faculty of Agricultural Technology, University of Tehran (Abureihan Campus) in 2012-2013. Factorial experimental was conducted based on a randomized complete block design with three replications. The irrigation factor was water deficit stress including irrigation when soil moisture reached 30% of field capacity (severe stress) and the second irrigation level was normal condition. Cultivation was carried out in May at a temperature of 22 degrees Celsius, a photoperiod of 16 hours of light and with adequate humidity. The number of 60 medium plastic pots with the opening diameter of 15 cm and the height of 15 cm and the capacity of 2 kg were filled. Before planting, the seeds were broken by pulling soft sandpaper on the surface of the seeds and performing stratification, and the seed germination test was also performed. The day before planting, light irrigation was done, then seven seeds were planted in each pot at a depth of one centimeter and the surface of the soil was covered with cocopeat in order to protect the soil moisture. The soil of the pots were watered twice a day with a sprinkler until the stress was applied, and after reaching a height of 15 cm, Hoagland's solution 50% was used to feed the plants, and after 55 days from the time of planting and in the vegetative growth stage the morphology traits such as stem number, plant height, leaf number, internode number, internode length, leaf area, dry leaf weight and dry stem weight were evaluated. The weight method was used to adjust the soil moisture content. Excel software was used to draw graphs, and data was analyzed by SAS software, and mean comparisons were made using Duncan's method.

  Conclusion: Since wild genotypes Kermanshah 130 and Azarbayjan 175 were the most tolerate genotypes in this study they can be used as new sources of resistance in future breeding programs.