Journal de pathologie végétale et de microbiologie

Abstrait

Rhizoctonia Root Rot of Pepper (Capsicum annuum): Comparative Pathogenicity of Causal Agent and Biocontrol Attempt using Fungal and Bacterial Agents

Mannai S, Jabnoun-Khiareddine H, Nasraoui B and Daami-Remadi M

Rhizoctoniaroot rot of pepper (Capsicum annuum L.) is becoming serious in Tunisia. Comparative pathogenicity tests performed for Rhizoctonia solani isolates recovered from pepper and potato showed that Rhiz.7 and Rhiz.4 were the most aggressive. They reduced by 53.5%-91.4% the aerial part fresh weight of inoculated cv. Baklouti plants relative to control. Rhiz.7 decreased by 81%-88% the root fresh weight on cvs. Beldi and Baklouti. Various fungal and bacterial agents were tested against R. solani. Dual culture trials showed that Trichoderma harzianum, T. viride and Glicladiumvirensgrew and sporulated profusely over R. solani colonies and altered its hyphae. Pseudomonas huttiensis 69, P. aureofaciens 31 and Burkholderiaglathei 35 reduced pathogen growth by 9.71-12.87%. These bio-agents were tested for their effects on rhizoctonia root rot disease and pepper growth. On cv. Beldi, pre-emergence damping-off, noted after 15 days, was suppressed by 55 (for G. virens), 45 (for T. viride) and 50% (for T. harzianum). This inhibition reached 57.14% using Bacillus pumilus 420 and P. putida 227. Tested on pepper cv. Altar, all tested fungi decreased by 40% post-emergence damping-off, and significantly increased the plant height of R. solani -inoculated and treated plants by 21.13 (for T. viride) to 36.34% (for T. harzianum) relative to control. P. aureofaciens 314 and P. putida 227 completely suppressed R. solani post-emergence expression. Treatments with P. aureofaciens 314, P. aureofaciens 31, Bacillus pumilus 420, P. fluorescens Pf and P. putida 227 induced a significant increase in their height compared to control. An improvement of the aerial part fresh weight by 54.54, 48.09 and 47.74%, as compared to control, was induced by P. aureofaciens 314, B. glathei 35 and P. huttiensis 69, respectively.