Acta Entomologica Sinica (2004) 47, 567-572

Juan Li, Jun-Huan Xu and Ming-Guang Feng (2004)
[Infectivity of a Pieris brassicae -derived Zoophthora radicans isolate and its new host-passage isolates against Plutella xylostella in relation to the phenoloxidase activity in the new host hemolymph after infection]
Acta Entomologica Sinica 47 (5), 567-572
Abstract: A Pieris brassicae-derived Zoophthora radicans isolate, R₀ , and its host-passage isolates R₁ - R₅, obtained by repeatedly passing through Plutella xylostella larvae, were bioassayed against the second instar larvae of the new host in the laboratory. The host-passage isolates tended to exhibit higher infectivity to the new host than the original isolate as the number of host passages increased. Based on the time-concentration-mortality modeling, the LC₂₀ (a lethal concentration to cause 20% mortality) on days 1 - 6 after exposure to spore showers was estimated as 14.7, 14.5, 9.0, 7.1, 6.0 and 5.5 spores/mm² respectively for R₀; 9.6, 5.0, 4.2, 3.6, 3.1 and 3.0 spores/mm² for R₁; 4.6, 2.9, 2.8, 2.5, 2.4 and 2.2 spores/mm² for R₃; and 5.2, 3.7, 3.2, 2.8, 2.6 and 2.6 spores/mm² for R₅. The phenoloxidase activities were significantly lower in the larval hemolymph stimulated by the infection of the host-passage isolates. There was also a positive correlation between the log₁₀ (LC₂₀) and the detected phenoloxidase activities among the isolates (0.85 < r² < 0.95). Apparently, the increased infectivity to the new host may result from an ability of the original Z. radicans isolate to avoid or overcome its immune defense in the course of the repeated new host passages.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
(original language: Chinese)
Database assignments for author(s): Jun-Huan Xu

Research topic(s) for pests/diseases/weeds:
biocontrol - natural enemies
Research topic(s) for beneficials or antagonists:
general biology - morphology - evolution
resistance/tolerance/defence of host

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Plutella xylostella
	Pieris brassicae
Zoophthora radicans (entomopathogen)	Plutella xylostella
Zoophthora radicans (entomopathogen)	Pieris brassicae