EVALUATION OF TRICHODERMA HARZIANUM AS A BIOCONTROL AGENT AGAINST MACROPHOMINA PHASEOLINA, THE COWPEA CHARCOAL ROT PATHOGEN

Abstract

Cowpea, Vigna unguiculata (L.) Walp. is susceptible to a large number of pathogenic organisms that cause diseases and bring about crop damage and yield loss. Macrophomina phaseolina (Tassi) Goid. is a soil-borne pathogen that causes charcoal rot infection (damping-off) in legumes and cereals. Endophytes are ubiquitous in all plant species in the world and have been found to possess antifungal attributes as they produce metabolites that naturally control plant diseases. Trichoderma based biocontrol agents synthesize antagonistic compounds (proteins, enzymes and antibiotics) and have better ability to promote plant growth and soil remediation activity. In this study, Trichoderma harzianum (Rifai) a biocontrol agent was evaluated against cowpea charcoal rot disease in-vitro and in-vivo. This work was carried out at the Plant Pathology and the screen-house of the Department of Crop Soil and Pest Management, Federal University of Technology, Akure, Ondo-State, Nigeria. The laboratory and screen- house experiments were laid out in completely randomized design (CRD) with three replicates. In the in-vitro experiment, the antagonist inhibited the mycelial growth of M. phaseolina in all the treatment methods applied. The highest percentage inhibition was recorded on 72 hours prophylactic inoculation of T. harzianum while the lowest was recorded on 72 hours inoculation of M. phaseolina before T. harzianum with 93.3% and 29.4%, respectively. The higher the number of days the antagonist had established itself before the inoculation of pathogen, the higher the mycelial growth inhibition on the pathogen. The seed treated at 108 conidia/ml of T. harzianum (antagonist) gave the highest mean value in most of the parameters evaluated when compared with other treatment methods. However, it was observed that cowpea in the control pots where the plants were inoculated with M. phaseolina only had the lowest height, number of leaves, leaf area and higher disease incidence and severity across the weeks. It was also observed that plants in the control pots did not produce flowers and pods throughout the experiment.