摘 要：
源于大菜粉蝶Pierisbrassicae的根虫瘟霉Zoophthoraradicans菌株R0 通过反复转染小菜蛾Plutellaxylostella而分别获得转染菌株R1 、R3和R5。用这些菌株对小菜蛾 2龄幼虫进行生物测定 ,发现菌株对寄主的侵染力有随转染次数增加而增强的趋势。接种后第 1～ 6天 ,R0 的LC2 0 (孢子数 mm2 )分别为 14 7、14 5、9 0、7 1、6 0和 5 5 ;R1 的LC2 0 分别为 9 6、5 0、4 2、3 6、3 1和 3 0 ;R3的LC2 0 分别为 4 6、2 9、2 8、2 5、2 4和 2 2 ;R5的LC2 0 分别为 5 2、3 7、3 2、2 8、2 6和 2 6 ,接种后同一天菌株R3的LC2 0 值最小即侵染力最强。各菌株感染小菜蛾幼虫后可显著激活寄主血淋巴中的酚氧化酶活性 ,但R1 、R3和R5对酚氧化酶的激活程度显著低于原始菌株R0 。各菌株对小菜蛾的侵染力强弱指标log1 0 (LC2 0 )与其侵染后寄主血淋巴酚氧化酶活性呈明显正相关 (0 85
译 名：
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
作 者：
LI Juan, XU Jun-Huan~*, FENG Ming-Guang (Institute of Microbiology, College of Life Sciences, Zhejiang University, Hangzhou?310029, China)
关键词：
Zoophthora radicans; Plutella xylostella; host passage; phenoloxidase activity; infectivity
摘 要：
A Pieris brassicae-derived Zoophthora radicans isolate, R_0, and its host-passage isolates R_1-R_5, 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 LC_(20) (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/mm~2 respectively for R_0; 9.6, 5.0, 4.2, 3.6, 3.1 and 3.0 spores/mm~2 for R_1; 4.6, 2.9, 2.8, 2.5, 2.4 and 2.2 spores/mm~2 for R_3; and 5.2, 3.7, 3.2, 2.8, 2.6 and 2.6 sproes/mm~2 for R_5.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 log_(10) (LC_(20)) and the detected phenoloxidase activities among the isolates (0.85
