Abstract

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 andSolanum 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.

Key words: antagonism, beneficial micro-organisms, biological control, Glomus deserticola, Pseudomonas spp., Pythium aphanidermaturm.