Kong Hailong, Liu Zhonglin, Yang Pingjun, Yuan Lin, Jing Wanghui, Dong Chuanlei, Zheng Minyuan, Tian Zhen, Hou Qiuli, Zhu Shude
College of Horticulture and Plant Protection, Yangzhou University, Wenhui East Road, NO. 48, Yangzhou 225009, China.
Suzhou Plant Protection and Plant Quarantine Station, Stadium Road, NO. 4, Suzhou 215006, China.
Insects. 2020 Dec 2;11(12):857. doi: 10.3390/insects11120857.
It has been reported that some phase-polyphenic insects from high-density conditions are more resistant to pathogens than those from low-density conditions. This phenomenon is termed "density-dependent prophylaxis" (DDP). However, whether non phase-polyphenic insects exhibit DDP has rarely been elucidated. The diamondback moth (DBM), , one of the most destructive insect pests affecting cruciferous crops, is non phase-polyphenic. In this study, the resistance of DBM larvae to granulosis virus ( GV) and their immune response to the virus when reared at densities of 1, 2, 5, 10, 15, and 20 larvae per Petri dish were investigated under laboratory conditions. Compared with larvae reared at lower densities, larvae reared at moderate density showed a significantly higher survival rate, but the survival rate significantly decreased with further increases in rearing density. Furthermore, the phenoloxidase, lysozyme and antibacterial activity and total hemocyte count in the hemolymph of the larvae, regardless of whether they were challenged with the virus, from different larval densities corresponded to the observed differences in resistance to GV. These results demonstrated that larvae exhibited DDP within a certain limited density. This study may help to elucidate the biocontrol effect of different density populations of by granulosis virus and guide improvements in future management strategy.
据报道，一些处于高密度条件下的多型性昆虫比处于低密度条件下的昆虫对病原体具有更强的抵抗力。这种现象被称为“密度依赖型防御”（DDP）。然而，非多型性昆虫是否表现出DDP却鲜有研究。小菜蛾是影响十字花科作物的最具破坏性的害虫之一，它是非多型性的。在本研究中，在实验室条件下，研究了每培养皿饲养1、2、5、10、15和20只小菜蛾幼虫时，小菜蛾幼虫对颗粒体病毒（GV）的抗性及其对该病毒的免疫反应。与低密度饲养的幼虫相比，中等密度饲养的幼虫存活率显著更高，但随着饲养密度进一步增加，存活率显著下降。此外，无论是否受到病毒攻击，来自不同幼虫密度的幼虫血淋巴中的酚氧化酶、溶菌酶和抗菌活性以及血细胞总数都与观察到的对GV抗性差异相对应。这些结果表明，小菜蛾幼虫在一定有限密度范围内表现出DDP。本研究可能有助于阐明颗粒体病毒对不同密度小菜蛾种群的生物防治效果，并指导未来管理策略的改进。
