Isolation and evaluation of culture media for mycelia growth of an emerging faba bean (Vicia faba L.) gall-forming disease causal agent in Ethiopia

[摘要] The current study aimed to identify suitable preliminary culture media for the isolation of faba bean gall-forming disease causal agent and confirm by pathogenicity test. Five separate media were evaluated for isolation. Infected faba bean stem disc and the mycelial disc of a pure isolate of the test pathogen were used for the in-vitro pathogenicity test on detached leaves. Pots filled with sterilized field soil were arranged in complete random block design and sown with disease susceptible FB-26869 faba bean health seeds for pot pathogenicity test. Pycnidium of the test pathogen appears filled with mature conidia and scattered inside the infected cells. At the initial stage, it was difficult to isolate the disease causal agent on the Potato Dextrose Agar medium. The Coon’s medium was found to be suitable for the preliminary isolation of the test pathogen and showed statistically significant mycelial growth (90.00 mm), while Malt Extract Agar and Tryptone Soy Agar thfavors a large number of conidia production at 14 day of the incubation period. The Chlamydospore and conidia of the isolates were similar to Peyronellaea pinodella and Phoma related species. The optimum mycelial growth of the isolates was 0recorded at temperature 20 C and pH value 6.50 on both Coon’s and Potato Dextrose Agar medium. No significant differences (P > 0.05) were recorded among leaf lesions caused by infected stem and mycelial discs. All the tested isolates exhibited similar virulence levels both in-vitro and in pot experiments. The disease incidence and severity were significantly (P ≤ 0.05) affected by seasonal variations. The highest percent severity index (91 – 95 %) was recorded from June to September. Synthetic culture media which inhabits other fast-growing fungus favors the mycelial growth of the test pathogen. The molecular characterizations were recommended for further confirmation.

[学科分类] 生物科学（综合）

[关键词] culture media;detached leaf;faba bean;gall-forming disease;pathogenicity