Microbes for Legume Improvement by Almas Zaidi Mohammad Saghir Khan & Javed Musarrat

Author:Almas Zaidi, Mohammad Saghir Khan & Javed Musarrat
Language: eng
Format: epub
Publisher: Springer International Publishing, Cham

9.2.1.2 N2-Fixing Symbiotic Bacteria

Associative and symbiotic N2-fixing bacteria are fundamental in plant N nutrition (Olivares et al. 2013). The N2-fixing symbiotic bacteria belonging to different genera, collectively termed as “rhizobia,” are able to fix N2 in symbiosis with legume plants (Olivares et al. 2013; de Bruijn 2015). How these bacteria interact with legume roots to form N2-fixing nodules and the molecular aspect determinants of host specificity in the rhizobia–legume symbiosis are described elsewhere in this book. Other bacteria, from the genus Frankia (actinomycetes) are known to form N2-fixing nodules on the roots of the so-called “actinorrhizal” plant species. The associative bacteria, like Azospirillum, colonize root surfaces and establish diazotrophic rhizocenosis with the plant and can even invade intercellular tissues; however N2-fixing structures are not formed (Gutiérrez-Mañero and Ramos-Solano 2010; Bashan et al. 2011; Olivares et al. 2013). Azospirillum enhance N supply to the plant but act mainly by increasing the production of auxin-type phytohormones, which affect the rooting patterns thereby benefiting plant nutrient uptake from soil rather than as N2-fixing bacteria (Dobbelaere et al. 2001).

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