Inhibitory Potential of Some Fungal Antagonists on Cercospora beticola the Causal agent of Cercospora Leaf Spot Disease on SugarBeet, Under Laboratory and Greenhouse Conditions

In this study, antagonistic potential of fungal agents inhabiting rhizosphere of sugarbeet were evaluated against Cercospora beticola, the causal agent of sugarbeet leaf spot disease. For this purpose, 15 fungal isolates were recovered from rhizosphere of sugar beet plants. After preliminary screening of their antagonistic potential, three isolates were selected for further antagonistic assay. Isolates were identified based on the sequence data of ITS-rDNA region. The identity of isolates was determined as Trichoderma harzianum, Acremonium strictum and Geliocephalis sp. Three additional antagonistic fungi namely T. harzianum (T22), T. harzianum (Ta) and Hansfordia pulivinanta (Ha) were also included in current experiment. The results obtained in this study showed that all of the antagonists significantly inhibited the growth of C. beticola in compare to the control. In dual culture and volatile secondary metabolite assays T. harzianum T22 showed the highest inhibitory effect and A. strictum and Geliocephalis showed lowest inhibitory effect on C. beticola. In non-volatile secondary metabolite (autoclaved and non- autoclaved) assay, the highest and lowest inhibitory effects were recorded for T. harzianum and A. strictum, respectively. Antagonistic potential of Trichoderma isolates were further evaluated under greenhouse conditions in three different statuses including application of antagonists prior to, simultaneous and after inoculation of C. beticola on sugar beet leaves. The obtained results showed that both Trichoderma isolates significantly reduced the disease severity in compare to the control.