African Journal of Biotechnology Vol. 6 (3), pp. 190-197, 5 February 2007   

ISSN 1684–5315 © 2007 Academic Journals        

Full Length Research Paper

Pseudomonads and symbiotic micro-organisms as biocontrol agents against fungal disease caused by Pythium aphanidermatum

NWAGA^1* Dieudonné ; FANKEM² Henri. ; ESSONO OBOUGOU³ Germain; NGO NKOT² Laurette and RANDRIANANGALY^{3, 4 y} Jean Stephan

¹Laboratory of Soil Microbiology, Biotechnology Centre, University of Yaoundé I. P.O. Box 812 Yaoundé, Cameroon.

²Department of Plant Biology, Faculty of Science, University of Douala. P.O. Box 24157, Douala, Cameroon.

³Department of Crop Protection, Faculty of Agriculture and Agricultural Science, University of Dschang.

⁴Alarobia lot II I 68 GAL, Antananarivo 101, Madagascar.

*Corresponding author. E-mail: dnwaga@yahoo.fr 

^yPermanent address: Alarobia lot II I 68 GAL, Antananarivo 101, Madagascar. Phone: (237) 993 18 71.

Accepted 8 December, 2006

Experiments were undertaken to assess the antagonistic aptitude of Pseudomonas spp. alone or associated with mycorrhizal fungi on Pythium aphanidermaturm, the causal agent of seedlings damping-off and stem rot of cowpea (Vigna unguiculata L. Walp). Evaluation was made using selected strains of pseudomonad (Pseudomonas fluorescens, P. putida and Pseudomonas sp.) isolated from V. unguiculata and Solanum tuberosum rhizospheric soils collected in three agroecological zones of Cameroon. Cultures were conducted on agar plates and in liquid media to evaluate the antagonistic capacity of those strains against Pythium aphanidermaturm and to evaluate their biocontrol activity in protecting cowpea plants. The results showed a direct inhibition of the pathogenic fungus by these bacteria. P. fluorescens used alone against Pythium aphanidermaturm, provided a reduction of the disease index from 3.44 to 1.06. When the arbuscular mycorrhizal fungi Glomus deserticola is associated to P. fluorescens, the disease index dropped to 0.13, confirming the synergistic effect of those beneficial micro-organisms.