Mwanza Patrick, Dealtry Gill, Lee Michael, Moore Sean
Department of Human Physiology, Nelson Mandela University, Gqeberha 6001, South Africa.
Centre for HRTEM, Nelson Mandela University, Gqeberha 6001, South Africa.
Pathogens. 2023 Apr 13;12(4):590. doi: 10.3390/pathogens12040590.
Cryptophlebia leucotreta granulovirus (CrleGV), a double-stranded DNA virus (genus , family ), is highly infective to the citrus insect pest . The South African isolate CrleGV-SA is formulated into a commercial biopesticide and registered for use in several countries. In South Africa, it is used as a biopesticide in a multi-faceted integrated pest management approach for citrus crops involving chemical and biological control methods. The virus nucleocapsid is surrounded and protected by an occlusion body (OB) composed of granulin protein in a crystalline matrix. Like all other baculoviruses, CrleGV is susceptible to ultraviolet (UV) radiation from sunlight. This reduces its efficacy as a biopesticide in the field and necessitates frequent respraying. UV damage to baculovirus biopesticides is detected by means of functional bioassays. However, bioassays do not give an indication of whether any structural damage has occurred that may contribute to functional loss. In this study, transmission electron microscopy (TEM) was used to observe damage to the OB and nucleocapsid (NC) of CrleGV-SA, following controlled UV irradiation in the laboratory to mimic field conditions. The resultant images were compared with images of non-irradiated CrleGV-SA virus. TEM images of irradiated CrleGV-SA samples revealed changes to the OB crystalline faceting, a reduction in the size of the OBs, and damage to the NC following UV exposure for 72 h.
柑橘小实蝇颗粒体病毒（CrleGV）是一种双链DNA病毒（属，科），对柑橘害虫具有高度感染性。南非分离株CrleGV-SA被制成商业生物农药，并在多个国家注册使用。在南非，它被用作生物农药，用于柑橘作物的多方面综合害虫管理方法，其中涉及化学和生物防治方法。病毒核衣壳被由颗粒蛋白在晶体基质中组成的包涵体（OB）包围和保护。与所有其他杆状病毒一样，CrleGV易受阳光紫外线（UV）辐射的影响。这降低了其在田间作为生物农药的功效，因此需要频繁重新喷洒。杆状病毒生物农药的紫外线损伤通过功能生物测定来检测。然而，生物测定并不能表明是否发生了可能导致功能丧失的任何结构损伤。在本研究中，使用透射电子显微镜（TEM）观察在实验室中进行受控紫外线照射以模拟田间条件后，CrleGV-SA的OB和核衣壳（NC）的损伤情况。将所得图像与未照射的CrleGV-SA病毒的图像进行比较。照射后的CrleGV-SA样品的TEM图像显示，在紫外线照射72小时后，OB晶体刻面发生变化，OB尺寸减小，NC受损。
