菜青虫感染蜡蚧轮枝菌后的组织病理变化

对感病菜青虫Pieris rapae组织切片的观察研究表明, 蜡蚧轮枝菌Verticillium lecanii主要通过昆虫的体壁侵染虫体。菜青虫各龄幼虫在体壁接菌12 h后，附着在虫体表面的孢子即可萌发。2～3龄幼虫，蜡蚧轮枝菌菌丝24 h就可穿透体壁进入血腔，48 h可见脂肪体等器官发生病变; 4～5龄幼虫，36 h菌丝才可穿透体壁，48 h可见虫体内有部分菌丝体。侵入虫体内的菌丝对寄生组织没有选择性。菌丝首先在入侵的血腔中生长，然后侵入脂肪体和肌肉，随菌丝在虫体内的增殖，中肠、马氏管、丝腺等相继被侵染。受侵的组织器管均发生明显的病变，如体壁分离，脂肪体变形、溶解，肌纤维排列松散，中肠上皮细胞脱落并出现许多空泡等。

Histopathological changes of Pieris rapae (L.) larvae infected by Verticillium lecanii (Zimm.) viega

A histopathological study on Pieris rapae (L.) larvae infected by Verticillium lecanii (Zimm.) viegas showed that the fungi infected the insect body mainly by penetrating the cuticle. The conidia on the cuticle of P. rapae larvae germinated in 12 h after inoculation. The hyphae penetrated the cuticle of the 2nd and 3rd instar larvae in 24 h and pathogenesis started on their fat body in 48 h. The hyphae penetrated the cuticle of 4th and 5th instar larvae in 36 h. Some hyphae were observed inside the body in 48 h. Invasion of the hyphae upon the host tissues showed no significant selection. They grew in hemolymphs firstly and then entered the fat body and the muscle. As the hyphae grew, the mid gut and the malpighian tube and the silk gland were infected successively. Pathological changes occurred on all infected tissues and organs, including cuticle disintegration, malformation and dissolution of the fat body, loose muscle fibre layout, disappearance of cells of the midgut epithelium and vacuolization.