بررسي شاخص هاي مورفولوژي و انتخاب ژنوتيپهاي مقاوم يونجه در برابر تنش اسمزي

Evaluation of morphological and selection of tolerant genotypes in alfalfa (Medicago sativa L.) in response to osmotic stress.

Drought stress is one of the most important environmental factors in reduce of growth,development and production of plants. Alfalfa is a important forage plants in farms and ranglands.Suitable germination and drought tolerance alfalfa by selection of drought tolerant genotypes is very important .In order to this ,in the first experiment,influence of drought stress on percent and rate of germination,radicle and plumule growth of eight alfalfa accision namely, Baghdadi, Nikshahri,Ghareh,Yazdi, Siriver, Sequel,Ranger and Kodi have been measured.Stress was applied with PEG6000, and drought potentials were: Zero (control),-4,-8 and –12 bar.The data showed that intensity of reduction in different accision is was not the same in response to drought stress.There are the lowest change percentage in Yazdi and Nikshahri accsions and the highest in Ranger accision in the most of characters. In the second experiment,the selected accision namely,Yazdi,Nikshahri and Ranger were grown in hydroponic culture with different osmotic potentials (PEG6000).After 4 weeks,different parameters such as:Root lenght,shoot lenght,root lenght to shoot lenght ratio,number and surface of leaves,root,shoot and leaf dry weight were measured.Genotypes survived in high potential (-12 bar),were transferred to soil to set seeds. The result showed with increasing drought stress, above parameters decreased,while root lenght to shoot lenght ratio was increased.Yazdi alfalfa was the most tolerant and Ranger was the most sensitive accision in response to osmotic stress.