In-vitro antifungal activity of rhizospheric Bacillus spp. of faba bean (Vicia faba L.) in Bale Zone, South-eastern Ethiopia against Botrytis fabae and their Plant growth promoting traits

Bacillus species are potentially used to stimulate plant growth and to protect plants from phytopathogens. The antifungal activity of rhizospheric Bacillus isolates of faba bean ((Vicia fabae L.) from the districts of Bale zone, south-eastern Ethiopia against a phytopathogenic fungus Botrytis fabae were evaluated. Soil samples were collected from the rhizosphere of faba bean varieties (Shallo, Mosisa and Wolki) in the three districts of Bale Zone (Goba, Sinana and Dinsho) and screened for Bacillus spp. Dual culture assay and in-vitro techniques were employed for this study. Descriptive statistics and analysis of variance (ANOVA) with a General Linear Model were used for analysis of data. Difference among means were significant at P < 0.05. Sixteen Bacillus isolates were employed for in-vitro test and all of them were able to grow at high temperatures (50 °C and 55°C) and tolerated high NaCl (7–10%). All isolates exhibited in-vitro antifungal activity against B. fabae. The percent inhibition of radial growth significantly varied among Bacillus isolates and faba bean variety (P < 0.05), but not among districts (P > 0.05). The highest percent inhibition of radial growth was exhibited by Bacillus isolates G3 (96.53 ± 1.14) followed by isolate D12 (91.11 ± 2.94) and S5 (81.48 ± 3.20). Our Bacillus isolates exhibited an appreciable enzymatic activity, phosphate and ZnO solubilization activity. IAA and HCN were produced by most of the isolates. About 68.8% of our Bacillus isolates were positive for at least five of plant growth promoting rhizobacteria traits. The results of this study revealed a promising antifungal activity of Bacillus spp. against chocolate spot disease and for their plant growth promoting traits. Further in-vivo study is recommended for Bacillus isolates G3, D12 and S5 in focus as they could be potential inoculants in suppression of B. fabae and for increasing productivity of faba bean