BIOLOGICAL CONTROL OF ONION WHITE ROT (SCLEROTIUM CEPIVORUM BERK) USING NATIVE TRICHODERMA SPECIES

Onion white rot caused by Sclerotium cepivorum Berk is one of the serious fungal diseases limiting yield of onion in Ethiopia. For environmentally friendly and sustainable management of the disease, the antagonistic effect of eleven native Trichoderma species isolates belonging to T. harzianum, T. hamatum and T. spirale were tested against a S. cepivorum pathogen under in-vitro and greenhouse conditions. Dual culture interaction method was used to assess in vitro antagonism. The greenhouse bioassay on onion was performed in pots using artificial inoculation of the pathogen, and Trichoderma isolates were added as maize grain cultures. In dual culture interaction, all Trichoderma isolates tested significantly reduced mycelial growth of S. cepivorum. However, there was statistically significant (p < 0.001) difference among Trichoderma isolates in inhibiting radial growth of the pathogen. The highest mycelial growth inhibition (89.77%) of S. cepivorum was recorded from T. harzianum MK and T. harzianum Z (85.67%), whereas the lowest radial growth inhibition (62.53%) was observed from T. hamatum KB. In greenhouse experiment, application of Trichoderma isolates significantly reduced white rot disease in onion inoculated with S. cepivorum. The lowest onion white rot disease incidence (37.5%) and severity (10.97%) was recorded form T. harzianum MK followed by T. harzianum Z, which display 40% incidence and 12.58% severity. Plants received Trichoderma treatment had improved plant growth parameters and yield compared to the untreated control and fungicide treated plants. Trichoderma isolates that display the highest inhibition and lowest disease can be used as biocontrol agents for the management of S. cepivorum.