African Journal of Biotechnology Vol. 5 (16), pp. 1457-1463, 17 August 2006   

ISSN 1684–5315 © 2006 Academic Journals        

Full Length Research Paper

Water-condition effects on rhizobia competition for cowpea nodule occupancy

Tatiana Krasova-Wade¹*, Omar Diouf², Ibrahima Ndoye¹, Ciré Elimane Sall³, Serge Braconnier², and Marc Neyra^1,4

¹Laboratoire Commun de Microbiologie IRD/UCAD/ISRA, (LCM), Centre de Recherche de Bel Air, B. P. 1386, C.P. 18524 Dakar, Sénégal

²Centre d’Etude Régional pour l’Amélioration de l’Adaptation à la Sécheresse (CERAAS), B. P. 3320, Thiès Escale, Thies, Sénégal

³Institut Sénégalais de Recherche Agricoles (ISRA), B. P. 3120, Dakar, Sénégal

⁴Present address : Laboratoire des Symbioses Tropicales et Méditerranéennes (LSTM), Campus de Baillarguet, TA10/J, 34398 Montpellier Cedex 5, France

*Corresponding authors E-mail: Tania.Wade@ird.sn; Tel (221) 849 33 26. Fax: (221) 849 33 02.

Accepted 27 January, 2006

Two indigenous bradyrhizobia strains displaying different natural behaviours towards water regime (strain ORS 3257, nodulating more frequently in favourable-water conditions and strain ORS 3260, in limited-water conditions) were studied for their competitivity for nodulation of cowpea (Mouride cultivar) under favourable and limited water conditions in non-sterile soil. The nodule occupancy was studied by PCR-RFLP analysis. Both strains showed good competition with other indigenous rhizobia populations under favourable- and limited-water conditions. Competition between the inoculated strains in the mixture varied between water regimes. In non-limited-water conditions, strain ORS 3257 was the best competitor, whereas in limited-water conditions, strain ORS 3260 was the best competitor. Results indicated that screening of strains according to their environmental origin could ensure successful rhizobia inoculation.

Key words: Vigna unguiculata, bradyrhizobia, inoculation, competition, limited-water conditions.