Abstract:

In order to clarify the biological characteristics of Phytophthora nicotianae of tobacco black shank, and screen high-efficiency chemical agents, the cross method was used to measure the colony growth diameter under different media, carbon sources, nitrogen sources, pH, glucose concentrations and light treatments. And hemocytometer was used to determine the number of sporulation. The sensitivity of Phytophthora nicotianae to 30% flumorph, 68.75% fluopicolide·propamocarb hydrochloride, 64% oxadixyl mancozeb, 80% cymoxanil, 70% propineb, 75% chlorothalonil, 80% fosetyl-aluminum, and 20% copper thiophanate were determined by the method of toxic medium. The results showed that the tested strains grew well on the oat medium. After 5 days of culture, the strains grew to 8.5 cm. The colonies were white and the hyphae were dense. The carrot medium was beneficial to sporulation quantity, and the quantity was about 7.92×10⁷. The tested strains grew and sporulated better in beef extract (nitrogen source) and soluble starch (carbon source) medium. The growth rates of strains treated with different pH media were not significantly different, but the growth and sporulation were better in the pH range from 6 to 7. When the glucose concentration was 0.02 mmol/L, the growth and sporulation yield of the strains were significantly higher than those of other treatments. The tested strains had no significant difference under different light treatments, but the mycelium growth was denser under dark condition, which was beneficial to the sporulation. All 8 chemical agents had inhibitory effects on the tested strains, among which 30% flumorph and 68.75% fluopicolide·propamocarb hydrochloride had significant inhibitory effects on pathogenic bacteria, with EC₅₀ of 0.1640 and 2.3339 μg/mL, respectively.

Key words: tobacco, black shank, Phytophthora, biological characteristics, virulence determination