Biological control in vitro of Phytophtora megakarya, the causal organism of black-pod disease of cocoa (Theobroma cacao L.)

Abstract

Potential fungal antagonists of Phytophtora megakarya were isolated from leaves, pods and soil rhizosphere of cocoa plant. Trichoderma harzianum and Trichoderma Koningii were isolated and tested for their ability to inhibit growth of P. megakarya on Potato Dextrose Agar (PDA). In-vitro screening was carried out using techniques of dual-culture analysis. The two isolates of Trichoderma effectively inhibited radial growth in P. megakarya through hyperparasitism iin vitro. The antagonists proliferated in the dual culture with P. megakarya and significantly reduced the growth of the mycelia when compared with the control. T. Koningii showed a better antagonistic effect than T. harzianum on P. megakarya. Results also indicated that introducing the antagonists before the pathogen gave better inhibitory effects than the other treatments (pathogen before antagonist and antagonist simultaneously with pathogen).

Keywords: Biological control; Cocoa; Phytophtora megakarya, Trichoderma harzianum, Trichoderma koningii,

Moor Journal of Agricultural Research Vol. 6 (1&2) 2005 pp. 87-91