Tokyo University of Agriculture and Technology, Saiwai-cho, Fuchu-shi, Tokyo, 183-8509, Japan.
Invasive Insect Biocontrol and Behavior Laboratory, Beltsville Agricultural Research Center, USDA Agricultural Research Service, 10300 Baltimore Avenue, Beltsville, MD, 20705, USA.
Sci Rep. 2021 Sep 20;11(1):18820. doi: 10.1038/s41598-021-97426-w.
Coconut rhinoceros beetle (CRB), Oryctes rhinoceros, is a pest of palm trees in the Pacific. Recently, a remarkable degree of palm damage reported in Guam, Hawaii, Papua New Guinea and Solomon Islands has been associated with a particular haplotype (clade I), known as "CRB-G". In the Palau Archipelago, both CRB-G and another haplotype (clade IV) belonging to the CRB-S cluster coexist in the field. In this study, more than 75% of pheromone trap-captured adults of both haplotypes were Oryctes rhinoceros nudivirus (OrNV)-positive by PCR. No significant difference in OrNV prevalence between the haplotypes was detected. In PCR-positive CRB-G tissue specimens from Palau, viral particles were observed by electron microscopy. Hemocoel injection of CRB larvae with crude virus homogenates from these tissues resulted in viral infection and mortality. OrNV isolated from Palauan-sourced CRB was designated as OrNV-Palau1. Both OrNV-Palau1 and OrNV-X2B, a CRB biological control isolate released in the Pacific, were propagated using the FRI-AnCu-35 cell line for production of inoculum. However, the OrNV-Palau1 isolate exhibited lower viral production levels and longer larval survival times compared to OrNV-X2B in O. rhinoceros larvae. Full genome sequences of the OrNV-Palau1 and -X2B isolates were determined and found to be closely related to each other. Altogether these results suggest CRB adults in Palau are infected with a less virulent virus, which may affect the nature and extent of OrNV-induced pathology in Palauan populations of CRB.
椰子犀甲（CRB），又称非洲巨犀金龟，是太平洋地区棕榈树的害虫。最近，在关岛、夏威夷、巴布亚新几内亚和所罗门群岛，报告了显著程度的棕榈树受损，这些受损与一种特殊的单倍型（分支 I）有关，称为“CRB-G”。在帕劳群岛，CRB-G 与另一种属于 CRB-S 群的单倍型（分支 IV）在野外共存。在这项研究中，超过 75%的两种单倍型的信息素诱捕成虫通过 PCR 检测为 Oryctes rhinoceros nudivirus（OrNV）阳性。未检测到两种单倍型之间的 OrNV 流行率存在显著差异。在来自帕劳的 PCR 阳性 CRB-G 组织标本中，通过电子显微镜观察到病毒粒子。用这些组织的粗病毒匀浆对 CRB 幼虫进行血腔注射，导致病毒感染和死亡。从帕劳来源的 CRB 中分离到的 OrNV 被指定为 OrNV-Palau1。OrNV-Palau1 和 OrNV-X2B，一种在太平洋释放的 CRB 生物防治分离株，均使用 FRI-AnCu-35 细胞系进行繁殖，以生产接种物。然而，与 OrNV-X2B 相比，OrNV-Palau1 分离株在 O. rhinoceros 幼虫中的病毒产量水平较低，幼虫存活时间较长。确定了 OrNV-Palau1 和 -X2B 分离株的全基因组序列，发现它们彼此密切相关。总之，这些结果表明帕劳的 CRB 成虫感染了一种毒力较弱的病毒，这可能影响帕劳 CRB 种群中 OrNV 诱导的病理学的性质和程度。
