ANTIFUNGAL EFFECTS OF TRICHODERMA ASPERELLUM (LIERKF) ON SCLEROTIUM ROLFSII, (SACC) THE CAUSAL ORGANISM OF WHITE MOULD DISEASEOF TOMATO (SOLANUM LYCOPERSICUM L.)

Abstract

Trichoderma spp are fungi with worldwide distribution. Some occur as endophytes while others are found in the soil and plant debris. Recent research findings suggest that Trichoderma strains can reduce significantly the incidence and severity of some fungal induced crop diseases. It was on the basis of this that Trichoderma asperellum was evaluated as a bio-control agent against the white mould disease of tomato, caused by Sclerotium rolfsii, both in vitro and in vivo. In the in vitro experiment, the dual culture technique was used and T. asperellum showed 60% inhibition of the mycelial growth of S. rolfsii when it was inoculated 24hrs prior to the introduction of S. rolfsii. This was significantly higher than when S. rolfsii was inoculated first, giving only 20% inhibition. In the in vivo experiment, three concentrations of 107, 105 and 103conidia /ml of T. asperellum were evaluated, and each concentration was used as seed treatment, prophylactic and curative application. A fungicide Mancozeb was also used as a treatment while the zero treatment had no control agent applied onto the S. rolfsii infected tomato seedlings. The control was healthy uninfected tomato plant. The different concentrations of T. asperellum were used to moistened healthy tomato seed as a seed treatment agent for five days, and then transplanted into experimental buckets. Prophylactic application involved foliar application of the different concentrations of T. asperellum on two weeks healthy tomato seedlings, followed by covering of the experimental pots with transparent polythene for 24hours before the introduction of S. rolfsii suspension. Curative application involved initial application of S. rolfsii suspension on two weeks healthy tomato seedling, and then covered with transparent polythene for 24hrs before the introduction of the different conidial concentration of T. asperellum. Each treatment was replicated thrice in a completely randomized design (CRD). It was observed that tomato yield was significantly higher in the seed treatment and preventive approach when compared to other methods of treatments. Concentration of T. asperellum at 105/ml conidia when applied prophylactically gave the highest antifungal effects and control of white mould disease of tomato. All T. asperellum treated plants recorded the highest brix value when compared to other treatments. However, T. asperellum at 105conidial/ml gave the best performance in growth parameter and recorded the least incidence and severity of white mould disease of tomato with a significant different over other methods of treatment. Trichoderma asperellum can therefore be used as a bio-control agent of S. rolfsii the causal organism of white mould and stem rot diseases of tomato.