In vivo Assay for Antagonistic Potential of Fungal Isolates against Faba bean ( Vicia faba L. ) Chocolate Spot ( Botrytis fabae Sard. )

Abstract

Due to its high protein content, faba bean (Vicia fabae L.) leaves harbor many microorganisms besides Botrytis fabae. The objective of this study is to explore fungal isolates residing on faba bean leaves and evaluate their antagonistic potential against B. fabae. For this matter, 236 leaf samples were collected from different districts of West Hararghe and Bale zones. Out of which 72 fungal species were isolated and evaluated for their in vivo biocontrol potential against chocolate spot (B. fabae Sard.). The in vivo assay was conducted in two stages where detached leaf test and intact leaf test was involved. Significant difference (p<0.05) resulted among fungal isolates to affect incubation period (IP) and disease severity (DS) on local and Shalo cultivars on detached leaf. Isolates GO2-3, GB6-3, S16-2, A12-1 and 52-BT resulted incubation period of 3.7 - 4.7 days, where it was 2 days on untreated control of both cultivars. Lower disease severity was recorded from the leaf treated by GO2-3 and S16-2 on local and GO3-2 on Shalo based on 1-4 rating scale. On intact plant, significant difference (p<0.05) among fungal isolates was resulted to affect IP, diseases incidence (DI) and DS. Higher IP was recorded from isolates GB6-3 (3.3), S16-2 (3), and GO3-2 (3 days) on local. GO3-2 showed better reduction (66.7 %) of chocolate spot incidence on Obse compared to the control (100%). Isolates S16-2, GO3-2 and GB6-3 resulted lower disease severity (percent severity index) of 35.6-51.1% as compared to control (73.3-84.4%) on the three cultivars.