6龄黏虫幼虫受球孢白僵菌侵染后生长发育及体内成瘤反应的变化

为探讨黏虫被球孢白僵菌侵染后生长发育情况及其体内的免疫反应,设置孢子浓度为104、5×104、105、5×105、106个/mL及5×106个/mL的球孢白僵菌菌液注射黏虫6龄初幼虫,研究球孢白僵菌对黏虫校正死亡率、羽化率、蛹重等生长发育指标的影响以及成瘤反应的浓度依赖效应。结果表明,6龄幼虫的校正死亡率随菌液浓度升高而逐渐增加。蛹重随菌液浓度增加而下降,但仅在106、5×106个/mL浓度处理时蛹重显著低于对照。同时,在孢子浓度为5×105、106、5×106个/mL时羽化率较对照显著降低,雌雄成虫寿命也显著缩短,而6龄幼虫至成虫羽化的发育历期在105、5×105、106、5×106个/mL浓度处理时较对照显著延长。此外,白僵菌侵染诱发黏虫免疫成瘤反应,并且具有明显的时间和浓度效应。注射84 h内,黏虫体内成瘤的数量随注射时间延长而递增,其后不再增加;同时,成瘤数量随着菌液浓度升高而增加,至106个/mL浓度时不再显著上升。该结果为揭示黏虫抵抗真菌侵染的免疫防御机制以及所产生的免疫代价提供了科学依据。

Changes in the development and nodule formation of the 6th-instar Mythimna separata larvae after infection by Beauveria bassiana

In order to explore the effects of Beauveria bassiana on the growth and development of Mythimna separata and its induction of immune response, the spore concentration was set to 104, 5×104, 105, 5×105, 106 and 5×106 spores/mL, respectively. The 6th-instar larvae of M.separata were injected with Beauveria bassiana spore suspensions to study the effects of B.bassiana on the growth and developmental indicators such as corrected mortality, emergence rate, pupa weight, and the injection concentration-dependent effect of nodule formation. The results showed that the corrected mortality of the 6th-instar larvae increased with increasing injection concentration. Pupa weight decreased with increasing injection concentration, but decreased significantly at the concentrations of 106 and 5×106 spores/mL. At the same time, the emergency rate decreased significantly with the increase of treatment concentration only under the concentration of 5×105, 106, 5×106 spores/mL. The life spans of male and female adults were also significantly shortened. The developmental duration from the 6th-instar larvae to emergency was significantly longer than that of the control at the concentration of 105 spores/mL and above. In addition, infection by B.bassiana induced immune responses of M.separata with significant time and concentration effects. Within 84 h after injection, the number of nodules increased with time, but did not increase significantly thereafter. In addition, the number of nodules increased with increasing fungal liquid concentration, but the number of nodules did not increase significantly when the concentration reached 106 spores/mL. The results provide a scientific basis for revealing the immune defense mechanism of M.separata against fungal infection and immune cost.