玫烟色拟青霉对小菜蛾幼虫的侵染过程及接菌方法对其致病力的影响

采用扫描电镜观察玫烟色拟青霉(Paecilomyces fumosoroseus)分生孢子在小菜蛾(Plutella xylostella)幼虫体表的萌发和侵染过程及玫烟色拟青霉孢子粉、孢子悬浮液和孢子培养液对小菜蛾幼虫的致病力.结果表明:小菜蛾幼虫体表嵴状突起结构区附着的孢子较多, 刺状突起结构区附着的孢子较少;刺状突起结构区附着的孢子萌发较早, 多数孢子在接菌后16 h开始萌发, 而嵴状突起结构区附着的孢子多数在20 h开始萌发, 在平缓结构区孢子萌发最迟.在嵴状突起结构区和刺状突起结构区, 多数孢子萌发后产生芽管, 直接以芽管侵入幼虫体壁, 少数形成附着胞侵染寄主.此外玫烟色拟青霉3种不同接菌方法对小菜蛾幼虫的侵染速率和致病力大小明显不同, 其中孢子培养液比孢子悬浮液和孢子粉对小菜蛾幼虫的侵染速率快, 接菌44 h虫体表现出明显的感病症状, 致死中时为3.18 d;孢子悬浮液和孢子粉处理的小菜蛾幼虫, 60 h虫体出现感病症状, 致死中时分别为4.20 d和4.34 d;而且致病力大小也存在明显差异, 接孢子粉的处理明显高于孢子悬浮液和孢子培养液, 小菜蛾幼虫6 d的死亡率达76.2%, 而其他两种处理小菜蛾幼虫6 d的死亡率仅为59.8%和58.5%.本研究结果表明, 小菜蛾幼虫的体表结构影响玫烟色拟青霉孢子在寄主体表的附着、萌发和侵入, 玫烟色拟青霉孢子粉对小菜蛾幼虫的致病力最强, 明显高于孢子悬浮液和孢子培养液.

Infection and pathogenicity of Paecilomyces fumosoroseus on Plutella xylostella

We examined the infection of Paecilomyces fumosoroseus via electron microscopy scan and pathogenicity of P. fumosoroseus conidia powder, conidia suspension liquid and conidia broth. Results show more conidia in acanthoid surface topography than in spinous surface topography. Conidia germinates earlier in spinous surface topography than in acanthoid surface topography and head area. Most conidia in pinous surface topography germinate 16 h after inoculation, whereas those in acanthoid surface topography germinate after 20 h, followed by those in head areas. Most conidia penetrate host cuticle with germ tubes in acanthoid surface topography and spinous surface topography of host while a few conidia does so with appressorium. Furthermore, infection velocity and pathogenicity are affected by inoculation method. Conidia from cultured broth infect hosts faster than those from suspension liquid and conidia powder. Pathogenic symptom of diamondback moths treated with conidia cultured broth is observed 44 h after inoculation, but those treated with conidia suspension liquid and conidia power is notable till after 60 h. LT50 of diamondback moth treated with conidia broth, conidia suspension liquid and conidia power are 3.18, 4.20 and 4.34 days respectively. Pathogenicity induced by conidia powder is strongest and mortality is 76.2% at 6 days after inoculation. In contrast, mortality from conidia suspension liquid and conidia broth at the same time is 59.8% and 58.5% respectively. Conidia power has the highest pathogenicity.