【作者】 张军；

【导师】 陈建新；

【作者基本信息】 中国农业大学 ， 农业昆虫与害虫防治， 2003， 硕士

【摘要】 本论文概述了虫草Cordyceps的研究概况；对紫外照射、温度和pH对虫草菌分生孢子萌发的影响、蛹虫草分生孢子感染家蚕Bombyx mori后的生理生化变化作了研究。此外，还通过石蜡切片观察了家蚕感染蛹虫草后的组织病理变化。 实验表明：与冬虫夏草分生孢子相比，蛹虫草分生孢子萌发受紫外光照射影响较大。85℃以上高温处理冬虫夏草分生孢子10min其不能萌发，51℃以上高温处理蛹虫草分生孢子10min其不能萌发。冬虫夏草分生孢子、蛹虫草分生孢子长时间保存在-80℃超低温冰箱后，萌发率不会受到太大影响。冬虫夏草分生孢子萌发的最适pH值为4，酸性致死pH值为1，碱性致死pH值为11。蛹虫草分生孢子萌发的最适pH值为5，致死pH值与冬虫夏草分生孢子相同。酸性环境中有利于虫草菌分生孢子的萌发。 蛹虫草分生孢子侵染5龄家蚕后，家蚕血淋巴中总糖、海藻糖、蛋白质、甘油脂含量与对照相比均有不同程度的下降，其中昆虫能量代谢的重要指标甘油脂含量下降最为显著。健蚕在实验第5日甘油脂含量为2.073mmol·L^-1，而处理组在接种后第5日甘油脂含量只有0.199mmol·L^-1，远远低于对照组健虫的水平，由此推测蛹虫草可能破坏了虫体的脂类代谢，脂肪体受侵染较为严重。海藻糖酶活性在侵染初期也明显降低。接种后家蚕体内的保护酶超氧化物歧化酶、过氧化物酶、过氧化氢酶活性也有较大变化，其中超氧化物歧化酶活性上升最为明显，在4日内由441.841U／mL升至601.255U／mL。 5龄家蚕被蛹虫草分生孢子侵染后，寄主血淋巴会发动防御作用，侵染后两天内在寄主体内没有发现大量的菌丝。第三天，菌体就利用寄主体内营养物质迅速繁殖，寄主体腔内菌丝和分生孢子增多，血淋巴变得浑浊。组织切片观察发现主要在表皮有萌发的孢子和菌丝，其它器官如马氏管、脂肪体、中肠、脑、丝腺中只有零星的菌丝，但在这些器官中，组织疏松，有大量黑点存在。第四天时个别幼虫开始死亡，多数个体第五天死亡。据此推测家蚕致死的主要原因是蛹虫草分生孢子在血腔中进行营养生长，菌丝不断增殖并侵入器官，使正常的体液循环受阻，造成生理饥饿，并引起组织细胞的机械破坏。同时菌丝在生长过程中可能会分泌毒素和代谢产物，使血液的理化性质发生变化，从而使寄主正常的代谢机能和形态结构发生变化，最终因不能维持正常的生命活动而死亡。更多还原

【Abstract】 In this thesis, the latest research status about Cordyceps were reviewed; effects of ultraviolet radiation, temperature and pH on germination of Cordyceps conidiophore were studied; physiological and biochemical changes of silkworm Bombyx mori during Cordyceps militaris infection were studied. By histological section observation, the histopathology changes of the infected larvae were illustrated. The results were as follows:Studies on the effects of ultraviolet radiation, temperature and pH on germination of Cordyceps conidiophore show that the germination of Cordyceps militaris conidiophore was drastically effected by the ultraviolet radiation, and the germination of Cordyceps sinensis conidiophore was drastically effected by different temperatures. The pH values fitted to the germination of Cordyceps conidiophore are under 7, and the optimum range is 4-5.When the 5th instar silkworm larvae were infected by Cordyceps militaris conidiophore, the content of haemolymph carbohydrates, trehalose, protein and glyceride differently decreased and the decrease of haemolymph glyceride was most obvious. The activity of haemolymph trehalase also decreased in infected silkworm. The activity of haemolymph SOD, POD and CAT were changed after the silkworm were infected. From 441.841U/mLto 601.255U/mL, the activity of SOD increased most significantly in four days.The results of histological section observations implied that, in the first two days, the haemocytes of the 5th instar silkworm larvae might take a defense response after they were infected by Cordyceps militaris conidiophore, and a large amount of hyphae can’t be found. The defense course could be finished in 2 days. Then, hyphae and conidiophore were found in the larval integument. There were little hyphae in other organs, but, except for malpighian tubules, most of organs were disintegrated and vacuolated. We can conclude that the toxin, which was secreted by Cordyceps militaris, may cause the death of infected larvae.更多还原