绿僵菌对“Q型”烟粉虱2龄若虫的致病性及与毒力关联的培养性状研究

Cultural Characteristics and Virulence of Metarhizium spp. to the 2nd Instar Nymphs of Bemisia tabaci

烟粉虱Bemisia tabaci(Gennadius)是我国农业上重要害虫,已对当今市场上多种杀虫剂产生严重抗性。本文研究了8株来自不同寄主的绿僵菌Metarhizium spp.菌株对Q隐种烟粉虱2龄若虫的致病性和与毒力关联的培养性状。结果表明,菌株Mf96对"Q型"烟粉虱2龄若虫具有很强的毒力,以1.0×108孢子/m L的孢子液接种到2龄若虫体表上,累积校正死亡率达89.5%,LT50为3.65 d,致死率明显高于其它菌株。以1.0×108、1.0×107、1.0×106和1.0×105孢子/m L悬浮液处理时,烟粉虱2龄若虫累计死亡率随浓度和接种后时间增加而增加,LC50为1.20×107孢子/m L。供试的8株绿僵菌菌株的胞外蛋白酶也被测定,菌株Mf96的胞外蛋白酶活性最高,达3.64 U/m L。菌株Mf96在SDAY培养基上,具有生长速度快、萌发率高和产孢量大等优点。菌株Mf96在烟粉虱的生物防治中具有较大的应用潜力。

Bemisia tabaci(Gennadius) is an important insect pest in China and has developed high resistance to many kinds of insecticides. In this study, 8 strains of Metarhizium spp., isolated from different hosts obtained from various geographical locations were evaluated for their virulence against the 2nd instar nymphs of the 'Q-biotype' B. tabaci. The results show that the M. flavoviride strain Mf96 had the highest virulence to the B. tabaci nymphs, with a corrected mortality of 89.5% at 7 d postr treatment and a LT50 value of 3.65 d at the concentration of 1.0×108 conidia/m L. With sprays at 4 concentrations(1.0×108, 1.0×107, 1.0×106 and 1.0×105 conidia/m L) of Mf96 conidial suspension, mortalities of the B. tabaci nymphs increased with treatment concentration and post-treatment time, and the LC50 value was 1.20×107 conidia/m L. Analysis of extracellular protease activities of the 8 strains reveals that enzyme activity(3.64 U/m L) of Mf96 was the highest among all the tested fungal strains. On SDAY medium, Mf96 showed such advantages as fast growth, quick germination and high sporulation, compared to other tested fungal strains. Therefore, Mf96 has a great potential in the biological control of the B. tabaci.