Non-rhizobia are the alternative sustainable solution for growth and development of the nonlegume plants

ABSTRACT

The major research focus for biological nitrogen fixation (BNF) has mostly been on typical rhizobia with legumes. But the newly identified non-rhizobial bacteria, both individually or in combination could also be an alternative for nitrogen supplementation in both legumes and nonlegume plants. Although about 90% of BNF is derived from a legume – rhizobia symbiosis, the non-legumes specially the cereals lack canonical nitrogen fixation system through root-nodule organogenesis. The non-rhizobia may colonize in the rhizosphere or present in endophytic/associative nature. The non-rhizobia are well known for facilitating plant growth through their potential to alleviate various stresses (salt, drought, and pathogens), acquisition of minerals (P, K, etc.), or by producing phytohormones. Bacterial symbiosis in non-legumes represents by the Gram-positive Frankia having a major contribution in overall fortification of usable nitrogenous material in soil where they are associated with their hosts. This review discusses the recent updates on the diversity and association of the non-rhizobial species and their impact on the growth and productivity of their host plants with particular emphasis on major economically important cereal plants. The future application possibilities of non-rhizobia for soil fertility and plant growth enhancement for sustainable agriculture have been discussed.

KEYWORDS:

• Plant growth promotion
• non-rhizobia
• symbiosis
• phytohormones
• agriculture

Acknowledgements

We are grateful to DBT, Gov. of India for financial support. We are thankful to Dr. Prithidipa Sahoo, Visva-Bharati University for her generous help on proofreading the manuscript.

Authors’ contributions

DP and SM conceptualize the research, DP performed data curation, wrote the original draft; SM supervised, reviewed and edited the Manuscript. Both authors approved the article for publication.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work is supported by the Department of Biotechnology, Govt. of India [Grant No- BT/PR23731/BPA/118/344/2017].

Notes on contributors

Dipanwita Patra

Dipanwita Patra completed her Bachelors in Microbiology from Raja Narendra Lal Khan Women’s College, Vidyasagar University, West Bengal, India in 2015 and completed her Masters from the same university in 2017. Currently, she is pursuing her Ph.D. in Laboratory of Molecular Bacteriology, Department of Microbiology, University of Calcutta. Her research mainly focused on nod-independent nodulation in legume-rhizobia symbiosis. She is also involved in research with endophytic bacterial association with non-legume plants.

Sukhendu Mandal

Dr. Sukhendu Mandal is currently working in the Department of Microbiology as an Assistant Professor. Dr. Mandal did his PhD from the Bose Institute, India on bacterial gene regulation. He did his postdoctoral research in Waksman Institute, New Jersey where he worked on the Mycobacterial RNA polymerase and anti-tuberculosis drug development. Dr. Mandal joined the University of Calcutta in 2012. His present primary research aim is to explore the extremophilic bacteria mainly the psychrophilic and halophilic one for identification of their active biomolecules. Another of his research interest is on bacteria-mediated environmental waste management with special emphasis on the rise of antimicrobial drug resistance.