Trichoderma Isolates from the Faba bean (Vicia faba L.) Rhizosphere for their Antagonistic Potential against Botrytis fabae Sard and Plant Growth-promoting Properties: An in vitro study

Trichoderma is a fungus used as a biological control agent for plant disease. Chocolate spot disease is one of the fungal diseases caused by Botrytis fabae Sard in faba beans. Thus, the present study was conducted to characterize Trichoderma isolates for their antagonistic efficiency against B. fabae and plant growth-promoting traits (PGPts). The effectiveness of the isolates against B. fabae varied from 7% to 88% upon 3-9 days of incubation (DOI) using the dual culture technique. Isolates AAUT21 and AAUT14 were the most effective, with 58-88 % of inhibition. The inhibition increased from 3-9th DOI from 13-64 % by sealed plate method. In the detached leaf assay, AAUT14 and AAUT44 showed significant differences from the controls (P < 0.05). Moreover, 63% and 95 % of the isolates were positive for indole-3-acetic acid and ammonia synthesis, respectively. In addition, the isolates solubilized tricalcium phosphate (TCP) in the range of 135-575 µg mL-1 upon 3-6 DOI. A negative correlation was also observed between pH and TCP solubilization (r = -.612**). Based on the cultural characteristics and tef1α gene sequence analysis, AAUT21, AAUT14, AAUT44, AAUT45, AAUT6, AAUT30, and AAUT4 were identified as T. afroharzianum AAUT21, T. harzianum AAUT14, T. tomentosum AAUT44, T. afroharzianum AAUT45, T. harzianum AAUT6, T. afroharzianum AAUT30, and T. tomentosum AAUT4, respectively. Trichoderma harzianum AAUT14 showed the best antagonistic feature against B. fabae along with PGPts production. Thus, T. harzianum AAUT14 can be a candidate to be used as a biofungicide for B. fabae and growth-promoting agent for faba bean plants. .