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Evaluation of MALDI-TOF mass spectrometry for the competitiveness analysis of selected indigenous cowpea (Vigna unguiculata L. Walp.) Bradyrhizobium strains from Kenya

Mathu Ndungu, Samuel; Messmer, Monika M.; Ziegler, Dominik; Thuita, Moses; Vanlauwe, Bernard; Frossard, Emmanuel and Thonar, Cécile (2018) Evaluation of MALDI-TOF mass spectrometry for the competitiveness analysis of selected indigenous cowpea (Vigna unguiculata L. Walp.) Bradyrhizobium strains from Kenya. Applied Micobiology and Biotechnology, online, pp. 1-4.

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Online at: https://doi.org/10.1007/s00253-018-9005-6

Summary

Cowpea N2 fixation and yield can be enhanced by selecting competitive and efficient indigenous rhizobia. Strains from contrasting agro-ecologies of Kilifi and Mbeere (Kenya) were screened. Two pot experiments were established consisting of 13 Bradyrhizobium strains; experiment 1 (11 Mbeere + CBA + BK1 from Burkina Faso), experiment 2 (12 Kilifi + CBA). Symbiotic effectiveness was assessed (shoot biomass, SPAD index and N uptake). Nodule occupancy of 13 simultaneously co-inoculated strains in each experiment was analyzed by matrix-assisted laser desorption/ionization time of flight (MALDI-TOF) mass spectrometry (MS) to assess competitiveness. Strains varied in effectiveness and competitiveness. The four most efficient strains were further evaluated in a field trial in Mbeere during the 2014 short rains. Strains from bacteroids of cowpea nodules from pot and field experiments were accurately identified as Bradyrhizobium by MALDI-TOF based on the SARAMIS™ database. In the field, abundant indigenous populations 7.10 × 103 rhizobia g−1 soil, outcompeted introduced strains. As revealed by MALDI-TOF, indigenous strains clustered into six distinct groups (I, II, III, IV, V and VI), group III were most abundant occupying 80% of nodules analyzed. MALDI-TOF was rapid, affordable and reliable to identify Bradyrhizobium strains directly from nodule suspensions in competition pot assays and in the field with abundant indigenous strains thus, its suitability for future competition assays. Evaluating strain competitiveness and then symbiotic efficacy is proposed in bioprospecting for potential cowpea inoculant strains.


EPrint Type:Journal paper
Keywords:Bradyrhizobium, Cowpea, Symbiotic effectiveness, Nodule occupancy, Protein profile, Bacteroid, Department of Crop Sciences, Plant Breeding, Plant Symbiosis
Subjects: Crop husbandry > Crop health, quality, protection
"Organics" in general > Countries and regions > Africa
Research affiliation: Belgium > Université de Liège (ULG)
Switzerland > ETHZ - Agrarwissenschaften
Switzerland > FiBL - Research Institute of Organic Agriculture Switzerland > Plant breeding
Kenya
ISSN:Print ISSN 0175-7598, Online ISSN 1432-0614
Deposited By: Messmer, Dr. Monika
ID Code:33100
Deposited On:30 Apr 2018 13:40
Last Modified:30 Apr 2018 13:43
Document Language:English
Status:Published
Refereed:Peer-reviewed and accepted

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