Rhizobium inoculants: Research progress and development status

Rhizobium-legumes symbiosis is an important way of legumes nitrogen fixation, which can provide 1/2-1/3 of nitrogen the legumes needed in their whole life. Therefore, the quantity of effective rhizobium in soil is an important decisive factor in legume production, while the use of rhizobium inoculants can effectively increase the quantity of rhizobium in soil. This paper reviewed the research progress and development status about the breeding and matching of highly effective rhizobium strains and the preparation and preservation of high-density rhizobium inoculants, analyzed the advantages and disadvantages of the breeding methods such as natural breeding, hybrid breeding, and mutation breeding, the agar matching methods, and the water culture matching methods, and summarized the general process and methods for inoculant preparation. The effects of various freezing-drying methods used in rhizobium inoculant preservation and of the applications of various protective agents on the preservation of rhizobium inoculants were also discussed. This review elaborated the preparation technology and the future development of rhizobium inoculants, which could provide a reference for the research and development of rhizobium inoculants.