The article presents the results of studying the source material of Elymus mutabilis for 2002-2021. The purpose of the research is to study and select a promising source material of Elymus mutabilis for the creation of a new variety of haymaking type of application in the conditions of Central Yakutia. The research was carried out covering 2 large agricultural landscapes and three uluses of Central Yakutia – Churapchinskaya (Ust-Aldasky ulus, Megino-Kangalassky ulus) and Prilenskaya (Khangalassky ulus). In 2002-2017, the study of Elymus mutabilis collection nurseries was conducted in the conditions of the Churapchinsky agricultural landscape. In 2018-2021, work continued in the breeding nursery in the conditions of the Prilensky agricultural landscape. 48 wild specimens were studied in collection nurseries, the seeds of which were collected during expeditions, the route of which passed through four districts of the Leno-Amginsky interfluve and floodplains of the Lena, Sinaya, Amga and Aldan rivers. As a result of studying the collection samples of Elymus mutabilis according to a complex of economically valuable signs and properties, 4 samples were selected for further breeding work, which are resistant to dusty smut, exceed the standard in yield of green mass by 16-35%, dry matter – by 6-49%, seeds – by 16-37%. The selected samples in 2012-2017 were tested with individual plant placement. During the growing season, a negative selection of low-shrub and low-leaved plants was carried out, as well as for resistance to dust smut. By the method of individual family selection, seeds were collected by families and 24 families were selected for further breeding work. In the Prilensky agricultural landscape for 2019-2021, six families from 24 families of Elymus mutabilis were allocated for further breeding work on economically valuable traits and properties.