Effects of Environment and Nutrition on Conidium Germination and Appressorium Formation byZoophthora radicans(Zygomycetes: Entomophthorales): A Pathogen of the Potato Leafhopper (Homoptera: Cicadellidae)
作者:
B. P. Magalhães,
R. A. Humber,
E. J. Shields,
D. W. Roberts,
期刊:
Environmental Entomology
(OUP Available online 1991)
卷期:
Volume 20,
issue 5
页码: 1460-1468
ISSN:0046-225X
年代: 1991
DOI:10.1093/ee/20.5.1460
出版商: Oxford University Press
关键词: Insecta;Zoophthora radicans;Empoascaspp.;fungal insect pathogen
数据来源: OUP
摘要:
Conidium germination and differentiation ofZoophthora radicanson water agar were investigated to identify requirements for the production of appressoria, the structures needed for virulence. Appressorium formation was more sensitive to environmental and nutritional changes than was conidium germination. Temperature affected both formation of germ tubes and appressoria, and the best temperature–nutrient interaction was found for appressorium formation at 25–30°C and 1% yeast extract. At 15°C, conidium germination was depressed independent of the nutrient concentration, and appressoria did not form. The volume of liquid overlaying the conidia and the yeast extract concentration individually affected appressorium formation. The best interaction between the volume of liquid and yeast extract concentration was the combination of a large volume of liquid medium (3 ml/962 mm2surface area) and 1% yeast extract. Of the 12 nitrogen sources tested, the best for germination and appressorium formation were yeast extract and Bacto-Soytone. Glucose, maltose, and starch were the best of the 12 carbon sources tested. Increasing osmotic pressure caused by different concentrations of maltose and polyethylene glycol adversely affected formation of germ tubes and appressoria. Subculturing did not affect formation of germ tubes, but the frequency of appressorium formation decreased after 12 transfers. The best pH for appressorium formation was between 7.0 and 7.2.Z. radicansproduced appressoria on cuticles of deadEmpoasca fabae(Harris) nymphs at 25°C in the dark.
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