Recent Developments in Biological Nitrogen Fixation in Plants

Dear Colleagues，

Nitrogen is the nutrient most required by plants, and it is frequently provided at unsatisfactory levels, limiting crop yields. However, the limitation in N supply is due to its scarce elemental abundance. On the contrary, nitrogen in the free state is one of the most abundant elements, accounting for almost 80% of the atmosphere, but most organisms cannot access atmospheric dinitrogen for metabolic purposes. Converting atmospheric dinitrogen into a usable form is restricted to the prokaryotes belonging to the Archaea and Bacteria domains. This process is called biological nitrogen fixation (BNF), and the microorganisms that perform it are collectively called diazotrophs. Although they share this common trait, they represent a wide diversity of phylogenetically and physiologically distinct genera and species that occupy different ecological niches.

Current research on nitrogen fixation is basic to finding the knowledge needed for agriculture research in the future. Biological nitrogen fixation (BNF) in plants is an essential mechanism for sustainable agricultural production and healthy ecosystem functioning. BNF by legumes and associative, endosymbiotic, and endophytic nitrogen fixation in non-legumes play major roles in reducing the use of synthetic nitrogen fertilizer in agriculture, increasing plant nutrient content, and in soil health reclamation. With the development of synthetic biology, various efforts have been undertaken to create so-called “N-self-fertilizing” plants capable of performing autonomous nitrogen fixation to avoid the need for chemical fertilizers.

Until the industrial synthesis of ammonia became possible at the beginning of the 20th century, BNF represented the main input of N in agriculture. Afterwards, the importance of BNF as a primary source of N for agriculture diminished. However, there is currently a growing concern about environmental issues. Agriculture is being focused on not only crop productivity but also on environmentally sustainable ways of production. Consequently, BNF has gained renewed relevance as an environmentally friendly technology able to supply N for agriculture. In addition to the rhizobial–legume symbiosis, other associations, with different levels of interaction between microorganisms and plants and different fixed N rates, have been studied and used in agriculture. This Special Issue welcomes all types of articles focusing on BNF, including original research and reviews.

Dr. Luciano Kayser Vargas
Dr. Bruno Brito Lisboa
Dr. Camille Eichelberger Granada
Guest Editors

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• diazotrophs
• rhizobia
• nodulation
• nitrogenase
• PGPR
• nitrogen fixation
• endophytes
• biofertilizers