关键词: 梨, 梢枯病, 出芽短梗霉, 生物学特性, 药剂筛选

Abstract:

To investigate the biological characteristics and fungicides sensitivity of the newly purified strains of Aureobasidium pullulans var. pullulans，which cause serious spot blight of pears. The effects of different carbon and nitrogen sources，pH values，temperatures and light conditions on the mycelial growth rate and spore productions were evaluated. The indoor toxicity of nine fungicides on the mycelium of A. pullulans var. pullulans was determined by the growth rate method of mycelium. The regression equation of virulence was established by the logarithm of concentration and probability value，the correlation coefficient（r）and estimate concentration of 50%（EC₅₀）btained. The results showed that the suitable temperature for mycelium growth and spore production of the pathogen was ranged from 15 ℃ to 25 ℃，and 20 ℃ was the optimum. When the temperature exceeds 35 ℃，the growth rate of mycelium becomes very slow. PDA was the optimal media for mycelium growth，while OA was the optimal media for spore production. Mannitol and Yeast extract were optimal for mycelium growth and spore production. A. pullulans var. pullulans could grow on the medium of pH 4-10. The optimum pH for mycelium growth and spore production was 5. Light promoted spore production and mycelium growth. The obvious ringlets observed on the colony with the cultural condition of alternating dark and light. The lethal temperature of conidia was 48.9 ℃. The sensitivity of A. pullulans var. pullulans to nine fungicides was evaluated by the growth rate method of mycelium. The results showed that the pathogen was more sensitive to 75% Trifloxystrobin · Tebutazol WDG，EC₅₀ < 0.01 mg · L^-1，followed by 70% Thiophanate-methyl WP，50% Carbrndazim WP，43% Fluopyram · Trifloxystrobin SC and 325 g · L^-1 Difenoconazole ·Azoxystrobin SC，0.01 mg · L^-1 < EC₅₀ < 1 mg · L^-1.

Key words: Pyrus prifolia, spot blight, Aureobasidium pullulans, biological characteristics, laboratory toxicity