Full Length Research Paper

Antagonist potential of Trichoderma indigenous isolates for biological control of Phytophthora palmivora the causative agent of black pod disease on cocoa (Theobroma cacao L.) in Côte d’Ivoire

J. Mpika^1,4*, I. B. Kébé¹, A. E. Issali², F.K. N’Guessan¹, S. Druzhinina³, M. Komon-Zélazowska³, C. P. Kubicek³ and S. Aké⁴

¹Laboratoire de Phytopathologie, CNRA, BP 808 Divo, Côte d’Ivoire.

²Station de Recherche sur le Cocotier Port Bouët Marc Delorme. 07 BP 13 Abidjan 07. Côte d’Ivoire.

³Institute of Chemical Engineering, Research Area Gene Technology and Applied Biochemistry, Vienna University of Technology, Getreidemarkt 9/E1665, A-1060 Vienna, Austria.

⁴Laboratoire de Physiologie végétale, UFR de Biosciences, Université de Cocody, 22 BP 582, Abidjan- Côte d’Ivoire.

*Corresponding author. E-mail: jmpika@yahoo.fr. Tel.: (225) 05.43.80.41.

Accepted 9 June, 2009

   Abstract

The biodiversity of Trichoderma isolates from cocoa rhizosphere in cocoa production areas of Côte d’Ivoire, and their antagonist potential with Phytophthora palmivora using in vitro assays and bioassays, were investigated and screened for field trials. A total of 135 isolates were analysed at the species level by using sequence analysis of ITS1 and 2 of the rRNA region and a fragment of translation elongation factor 1a (tef1) gene. Sixty-four isolates were identified as T. virens, 60 as T. harzianum, 7 as T. spirale, two as T. asperellum and two unidentified. Forty-three Trichoderma isolates were in vitro confronted with P. palmivora on agar plates, and their antagonist activity was further evaluated by the damages on leaf discs and detached pods. Twenty-five isolates reduced the mycelial growth of P. Palmivora more than 50%.  The isolate T17 assigned to T .virens was the best to reduce mycelium growth upto 97.9%. All of Trichoderma isolates with the exception of isolate T39 reduced foliar sensitivity to P. palmivora. Tweenty-six Trichoderma isolates reduced the pod sensitivity to P. palmivora more than 50%. Based on the combined analysis, T. virens T7, T. harzianum T40, T. asperellum T54 and T. spirale T4 isolates were selected for field trials.

Key words: Biodiversity, antagonist, in vitro assays and bioassays, Phytophthora Palmivora, Trichoderma, cocoa rhizosphere, Côte d’Ivoire.