大菜粉蝶根虫瘟霉菌株转染小菜蛾后侵染力变化及其与寄主血淋巴酚氧化酶活性的关系  

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：李娟[1] 徐均焕[1] 冯明光[1] 

机构地区：[1]浙江大学微生物研究所,杭州310029

出　　处：《昆虫学报》2004年第5期567-572,共6页Acta Entomologica Sinica

基　　金：国家自然科学基金项目 ( 3 0 0 70 0 2 5 ) ;浙江省自然科学基金项目 ( 3 0 2 0 16) ;国家科技部项目 (G2 0 0 0 0 162 0 8 0 4)

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 <r2 <0 95 ) ,表明R0 在对新寄主转染过程中逐渐获得了逃避或克服新寄主免疫防御的能力 ,从而增强对新寄主的侵染力。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<r^2<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.

关 键 词：根虫瘟霉 小菜蛾 寄主转染 酚氧化酶活性 侵染力 

分 类 号：Q965[生物学—昆虫学]