Nature and Science 2013;11(7) http://www.sciencepub.net/nature http://www.sciencepub.net/nature naturesciencej@gmail.com 124 In-vitro Biocontrol of Fungi Associated with Leaf Diseases of Tomato (Lycopersicon esculentum Mill.) using Trichoderma Species Tolulope S. Ewekeye, 1,2 Oyedamola A. Oke, 1 Oyinkansola B. Seriki, 1 Aminat T. Bello 1 1 Department of Botany, Lagos State University, Ojo, P. M. B. 0001, LASU Post Office, Ojo, Lagos, Nigeria 2 Department of Botany, University of Ibadan, Oyo State, Nigeria toluewekeye@gmail.com , damolaoke@gmail.com Abstract: Biological control potential of fungi isolated from roots of diseased tomato plants against fungi associated with foliar diseases of tomato was investigated in this study. Fungi associated with the diseased tomato leaves included Alternaria alternata, Fusarium solani, Phialophora melinii, Paecilomyces variotii, and Verticillium albo- atrium. Each fungus was paired against Trichoderma harzianum and Trichoderma koningii which were isolated from the rhizophere of the diseased plants. The antagonists (Trichoderma species) were paired simultaneously against the pathogen, the pathogen before the antagonist and the antagonist before the pathogen. For the timing of inoculation, pairing of the antagonist before the pathogen was the most effective, followed by simultaneous pairing, while pathogen before antagonist gave the least antagonism after nine days of inoculation. The mode of antagonism was found to be by competition for space, antibiosis and mycoparasitism. [Ewekeye T S, Oke O A, Seriki O B, Bello A T. In-vitro Biocontrol of Fungi Associated with Leaf Diseases of Tomato (Lycopersicon esculentum Mill.) using Trichoderma Species. Nat Sci 2013;11(7):124-128]. (ISSN: 1545- 0740). http://www.sciencepub.net/nature . 21 Keywords: Foliar diseases of tomato, Trichoderma, biological control, antagonist 1. Introduction Biological control is the inhibition of growth, infection or reproduction of one organism using another organism (Baker, 1987; Cook, 1993). Biological control of plant diseases has been considered a viable alternative method to manage plant diseases as against the use of chemical pesticides and cultural practices (Cook, 1993, Agrios, 2005). Biocontrol is environmentally safe and in some cases it is the only option available to protect plants against pathogens (Cook, 1993). Antagonists in biological control of plant pathogens are biological agents with the potential to interfere in the life processes of plant pathogens. (Cook and Baker, 1983). Antagonists of plant pathogen may be resident or introduced. Resident antagonists are part of the natural microbiota in soil or on roots, leaves or other plant parts, while introduced antagonists are those which are applied as cultures or prepared products to soil or plants (Dube and Podile, 1988). Different mode of actions of biocontrol-active microorganisms in controlling fungal plant diseases include hyperparasitism, predation, antibiosis, cross protection, competition for site and nutrient and induced resistance (Heydari and Pessarakli, 2010). The use of microorganisms that antagonize plant pathogens (biological control) is risk-free when it results in enhancement of resident antagonists. Biological control of fungal plant pathogens appears as an attractive and realistic approach and numerous microorganisms have been identified as biocontrol agents. Members of the Trichoderma genus are known as imperfect fungi, fast growing in culture and produce numerous green spores. They occur worldwide and are commonly associated with root, soil and plant debris. They have long been recognized as biological agents to control plant diseases. Trichoderma species have become popular biological agents to protect crops against plant pathogens all over the world. Researches have indicated that they can parasitize fungal pathogens and produce antibiotics (Tran, 2010). Trichoderma species have been investigated for eighty years (Basim et al., 1999). They have been used recently as biological control agents and their isolates have been commercially available of late (Loper and Buyer, 1991). Trichoderma affects a wide range of plant pathogens such as Fusarium, Verticillium, Alternaria, Rhizopus, Venturia, Enthothia, Phytophthora, Fusicardium. Living Trichoderma isolates produce metabolites which are antagonists to others in the soil environment. Trichoderma can also release compounds and extracellular enzymes known as trichodermin, which damage plant pathogen (Jones and Prusky, 2002). The colonies of Trichoderma have either loose or tuft colonies, which are correlated to structures of the conidiophores. Trichoderma are generally yellowish or light green in colour (Jones and Prusky, 2002). The use of biocontrol agents is presently gaining momentum as a supplement to chemical treatment in integrated disease management module. The fungal antagonists may compete for an ecological niche by