Neotropical legume tree Inga edulis forms N2-fixing symbiosis with fast-growing Bradyrhizobium strains

Leblanc Humberto A., Mc Graw Robert L., Nygren Pekka, Le Roux Christine. 2005. Neotropical legume tree Inga edulis forms N2-fixing symbiosis with fast-growing Bradyrhizobium strains. Plant and Soil, 275 : 123-133.

Résumé : Inga edulis Mart. is a tropical legume tree used for shade in coffee and cacao plantations and as a hedgerow in alley-cropping practices. Little information can be found concerning N2 fixation in this species. This study was conducted to characterize the rhizobia of I. edulis and determine if it is capable of fixing substantial amounts of N2. Four strains of fast-growing, Gram-negative rhizobia-type bacteria were isolated from I. edulis nodules. The strains were identified by sequencing of partial 16S-23S rDNA internal spacer region. Nitrogenase activity was determined using acetylene reduction assay (ARA). Dinitrogen fixation was measured under controlled conditions by the 15N isotope dilution technique using two non-N2-fixing reference species, Vochysia guatemalensis Donn. Sm, and Gmelina arborea Roxb. ex. Sm. Seedlings were grown in three growth media: native soil and naturally N-depleted sand amended to a low and high N level. The four strains of symbiotic bacteria were closely related to Bradyrhizobium japonicum and to Bradyrhizobium liaoningense. Nodules demonstrated nitrogenase activity as measured by ARA. Vochysia guatemalensis was a better non-N2-fixing reference than G. arborea. When V. guatemalensis was used as the non-N2-fixing reference, the estimate of the percentage of N fixed from atmosphere out of total N in I. edulis seedlings was ca. 40% in the two sand media treatments and 10% in the native soil.

Mots-clés Agrovoc : Fabaceae, Inga, Fixation de l'azote, symbiote, Bradyrhizobium

Classification Agris : P34 - Biologie du sol

Champ stratégique Cirad : Axe 1 (2005-2013) - Intensification écologique

Auteurs et affiliations

• Leblanc Humberto A., University of Missouri (USA)
• Mc Graw Robert L., University of Missouri (USA)
• Nygren Pekka, University of Helsinki (FIN)
• Le Roux Christine, CIRAD-FORET-PLANTATIONS (FRA) ORCID: 0000-0003-0668-3589

Source : Cirad - Agritrop (https://agritrop.cirad.fr/529698/)

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