Evaluation of fresh culture media for mycelial growth and conidial production of Botrytis fabae, causing chocolate spot on faba bean (Vicia faba L.)

Botrytis fabae incites chocolate spot, one of the most devastating fungal diseases infecting and constraining faba bean cultivation in Ethiopia. Culturing of B. fabae and mass production of its infective conidia has been very difficult for pathological researches on the disease caused by this fungus. Therefore, two in vitro experiments were conducted to evaluate influence of culture media on mycelial growth and sporulation of B. fabae. Ten and six separate media were evaluated for mycelial growth and sporulation, respectively. A 6 mm agar plug of fresh B. fabae culture was inoculated to each medium, arranged in CRD with 4 replications and were incubated at 22°C. Of the media tested, significantly highest (89.40 and 88.15 mm) mycelial growth were recorded on chickpea dextrose agar (CDA) and soybean dextrose agar (SBDA), respectively. Sabouraud dextrose agar supported the lowest (66.40 mm) mycelial growth 7 days after inoculation at 22°C. Significantly excellent conidial formation and spore count were recorded from Chrysanthemum flower dextrose agar (CFDA) medium (1.07 x 106/ml). Potato dextrose agar (PDA) was found inferior both in growth and sporulation of the fungus ad compared to those tested media which exhibited maximum mycelial growth and excellent sporulation. The overall results of this study indicated that cultural characteristics, mycelial growth and sporulation of B. fabae were influenced by media sources, implying that CDA and SBDA were best suited for mycelial growth. CFDA supported maximum sporulation and conidial production as compared to PDA medium. This study might be helpful for studying various aspects of B. fabae and further enhanced by complementing the tested media with different C, N and salt sources to investigate various biological and molecular characteristics of the fungus.