Survey of nitrogen fixation on endophytes isolated from root nodules of alder and service

Nitrogen is one of the most important elements needed by plants, but plants are unable to reduce atmospheric nitrogen into ammonia and use it directly for its growth. Nitrogen fixing microorganisms, with the process of nitrogen fixation, provide the nitrogen required for plant utilization and play an important role in soil fertilization. The aim of this study was to evaluate nitrogen fixation in endophytic microorganisms isolated from root nodules of alder (Alnus subcordata) and Russian olive (Elaeagnus angustifolia) in Golestan province. A total of 50 nodule specimens were collected and cultured on nitrogen-free medium. Microorganisms were identified using biochemical and molecular tests. Nitrogen fixation of isolates was also evaluated using acetylene reduction and gas chromatography (GC). The two genera of Streptomyces badius strain BL225 and Actinomadura citrae strain DSM 43461 were identified as endophytic actinobacteria, Cladosporium cladosporioides strain F1 and Cryptococcus victoriae strain p41A001 were found as Ascomycota and Basidiomycota phyla of fungal endophytes, respectively. Cladosporium cladosporioides strain F1 and Cryptococcus victoria strain p41A001 had a high ability in nitrogen fixation. The root nodules of alder (A. subcordata) and Russian olive (E. angustifolia) carry the endophytic microorganisms with nitrogen fixation ability, therefore, the endophytes can be used as biocontrol agents in agriculture.