Abstract:

The biological characteristics of the pathogen of sweetpotato scab (Elsinoe batatas) were studied and the methods of producing a large number of conidia in a short time by E. batatas on artificial medium were screened to provide the basis for resistance breeding of sweetpotato scab. Taking the E. batatas isolate CRI-CJ2 as research object, the mycelial growth rate method was utilized to measure the colonial diameter under different medium, pH values and illumination conditions. The concave slide pendent drop method was used to study the conidial germination rate under different temperature, pH values and illumination conditions, and the effects of the Fries liquid culture method, shaking method and mycelium coating method for inducing conidia production of E. batatas were compared. The results showed that the optimal medium for mycelial growth was PDA, the optimum pH value was 6-7, and the lethal temperature was 48℃ for 10 min. No significant differences were found in the mycelial growth between different illuminations, but the colour of colony turned bright red under continuous illumination condition. The optimum pH value for conidial germination was 5, the best temperature was 25℃, and the conidia could not germinate above 48℃ for 10 min. Illumination showed little effect on conidial germination. The conidial quantity of E. batatas was 7.09×10⁷ conidia/mL after 12 days of incubation by the mycelium coating method and the conidial germination rate was 24% after incubation for 24 hours, and the quantity and viability were higher than that by the shaking method. No conidia or sporogenous structure were observed by the Fries liquid culture method. Therefore, selecting appropriate medium and pH value could promote mycelial growth, and the mycelium coating method had the advantages of rapid sporulation and high conidial quantity and was a suitable method for E. batatas conidia induction.

Key words: sweetpotato scab, Elsinoe batatas, biological characteristics, conidia production, mycelium coating method