Evaluation of Rhizobacteria and Trichoderma Isolates From the Rhizosphere of Faba Bean (Vicia Faba L.) for their Potential In the Management of Chocolate Spot (Botrytis Fabae Sard.) Disease and Host Plant Growth-Promoting Properties

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Addis Ababa University


Faba bean (Vicia faba L.) is one of the legume grains used as a source of food for human. However, the productivity of the crop is less due to chocolate spot (Botrytis fabae Sard) in Ethiopia. The disease can be managed through the applications of fungicides such as MORE 720 WP and ORZEB 80 WP. Alternatively, an eco-friendly approach is initiated using Trichoderma and bacterial species to manage the disease. Therefore, in this study, Trichoderma and bacterial species were evaluated against Botrytis fabae under in vitro and in vivo conditions. The data were analyzed by SPSS version 24. The bacterial strains inhibited B. fabae (6-68%) upon 3-9 days in the dual culture method. The highest inhibition was recorded by B. tequilensis AAUB100 that displayed 80% and Serratia nematodiphila AAUB146b with 79% inhibition at 20% (v/v) of the culture filtrate. A 200-760 μg mL-1 of solubilized phosphate was also released upon 3-6 days by the isolates. Trichoderma harzianum AAUT14 was the most effective antagonist with more than 88% of B. fabae inhibition in the dual culture upon 9 days. The isolates of Trichoderma also showed inorganic phosphate solubilization that ranged from 135-509 μg mL-1 upon 3-9 days. Under the greenhouse study conducted using a completely randomized design, the disease incidence reduced by 36-50% on Ashebeka variety compared to the control (T1) in which T. harzianum AAUT14 and B. subtilis AAUB95 (T4) displayed the highest reduction (50%) of disease incidence upon 60 days. The disease severity reduction was much pronounced upon 80 days ranging from 41-55% compared to the disease severity, which did not show significant difference (p>0.05) between T4 and T5 (MORE 720 WP) upon 60 days. A 3.8-34% of disease incidence and 15-26 disease severity reduction was also observed upon 60 days on Hachalu variety. An area under disease progress curve (AUDPC) of 405.97% and 415.33% was displayed by T5 and T6 (ORZEB 80 WP), respectively on Ashebeka variety. Similarly, 377.98% by T5 and 412.48% by T6 of AUDPC was illustrated in Hachalu variety showing no significance difference (p>0.05) with T4. Under field conditions conducted using a completely randomized block design, the combination of Trichoderma harzianum AAUT14+B.subtilis AAUB95 (T4) reduced the disease incidence and severity showing no significance difference (p>0.05) with T5 upon 70 and 90 days. Nevertheless, in Hachalu variety (Trial 2), the treatment reduced the disease incidence from 23-51% and disease severity 37-54% upon 90 days. In addition, the AUDPC ranged from 1586.1-2250.0% in trial 1 and 1382.0-2454.5% in trial 2. The grain yield was also increased by 34% and 38% in trial 1 and 2, respectively over the controls by T4. In conclusion, the mixture of T. harzianum AAUT14 and B. subtilis AAUB95 or in some cases T. harzianum AAUT14 performed best in controlling chocolate spot and growth promotion of faba bean under greenhouse and field conditions.



AUDPC, Biocontrol, Chocolate Spot, Disease Severity, Fungicides, Inhibition, Yield