Abstract:
Late blight disease is a major cause of economic losses in tomato (Lycopersicon esculentum L.)
production in eastern Africa. The objective of this study was to evaluate the efficacy of Trichoderma
species in controlling late blight disease and their role on the growth of tomato. Trichoderma asperellum
and T. harzianum were isolated from two commercial products containing the antagonistic species.
Culture-based and molecular approaches, genomic DNA isolation and amplification, using ITS1 and
ITS4 universal primers, and sequencing, were used to characterise the products. Trichoderma
antagonistic effects against Phytophthora infestans (causative of tomato late blight) experiments
were conducted in vitro and in the greenhouse. The greenhouse experiment had five treatments;
namely, a negative control, Metalaxl-M, T. asperellum, T. harzanium and mixture of the two biocontrol
agents, laid out in a randomised complete block design. The experiment was carried out for 12 weeks,
with 3 weeks measurements intervals. Morphological and molecular characterisation confirmed the
organism in most of the commercial products as T. harzianum and T. asperellum. An inhibiting action
was observed on the P. Infestans mycelial growth, by the effect of T. asperellum (30.7%), and T.
harzianum (36.9%).Trichoderma spp. suppressed late blight disease in the greenhouse experiment.
These effects were specific to soil type, with the higher effectiveness realised in Ferralsols (27%
disease severity) and least in Nitisols (36% disease severity). Trichoderma harzianum and T.
asperellum resulted in higher above ground biomass of tomato of 31 and 19% increase over the
control, respectively. There is potential of biocontrol agents in reducing P. infestans effects in
tomatoes and in stimulating growth.
Key Words: Ferralsols, Lycopersicon esculentum, Metalaxl-M, Trichoderma asperellum
