Razi Vaccine and Serum Research Institute, Agricultural Research, Education and Extension Organization (AREEO), Karaj, Iran.
Iran Silkworm Research Center, Agricultural Research, Education and Extension Organization (AREEO), Rasht, Iran.
Arch Razi Inst. 2022 Aug 31;77(4):1473-1480. doi: 10.22092/ARI.2022.356482.1853. eCollection 2022 Aug.
Pebrine disease is the most important and dangerous disease of silkworm caused by as an obligate intracellular parasitic fungus. It has caused tremendous economic losses in the silk industry in recent years. Given the fact that light microscopy method (with low accuracy) is the only method for diagnosing pebrine disease in the country, transmission electron microscopy (TEM) and scanning electron microscopy (SEM) methods were adopted in this study for accurate morphological identification of the spores causing pebrine disease. Infected larvae and mother moth samples were collected from several farms (Parand, Parnian, Shaft, and Iran Silk Research Center in Gilan province, Iran). The spores were then purified using the sucrose gradient method. From each region, 20 and 10 samples were prepared for SEM and TEM analysis, respectively. In addition, an experiment was performed to evaluate the symptoms of pebrine disease by treating fourth instars with the spores purified for the present study, along with a control group. The results of SEM analysis showed that the mean±SD length and width of spores were 1.99±0.25 to 2.81±0.32 μm, respectively. Based on the obtained results, the size of spores was smaller than the () as the classic species that cause pebrine disease. In addition, transmission electron microscopy (TEM) pictures showed that the grooves of the adult spores were deeper than those of other species, Vairomorpha, and Pleistophora, and resembled in other studies. Examination of pathogenicity of the studied spores indicated that the disease symptoms in controlled conditions were similar to those in the sampled farms. The most important symptom in fourth and fifth instrars were the small size and no growth in the treatment group compared with the control group. Findings of SEM and TEM analysis showed better morphological and structural details of parasite compared with light microscopy, and demonstrated that the studied species were a native strain of specific to Iran, whose size and other characteristics were unique and introduced for the first time in this study.
微粒子病是由一种专性细胞内寄生真菌引起的蚕最严重和危险的疾病。近年来，它给丝绸工业造成了巨大的经济损失。鉴于该国唯一用于诊断微粒子病的方法是光镜法（准确性低），本研究采用透射电子显微镜（TEM）和扫描电子显微镜（SEM）方法对引起微粒子病的孢子进行准确的形态学鉴定。从伊朗几个农场（Parand、Parnian、Shaft 和伊朗丝绸研究中心，吉兰省）采集受感染的幼虫和母蛾样本。然后使用蔗糖梯度法纯化孢子。从每个地区，分别准备 20 个和 10 个样本进行 SEM 和 TEM 分析。此外，还进行了一项实验，用本研究纯化的孢子处理四龄幼虫，并与对照组一起，评估微粒子病的症状。SEM 分析结果表明，孢子的平均±SD 长度和宽度分别为 1.99±0.25 至 2.81±0.32 μm。根据获得的结果，孢子的大小小于（）作为引起微粒子病的经典物种。此外，透射电子显微镜（TEM）图片显示，成虫孢子的凹槽比其他物种（Vairomorpha 和 Pleistophora）的凹槽更深，与其他研究中的（）相似。对研究孢子的致病性研究表明，在对照条件下，疾病症状与采样农场相似。第四和第五龄幼虫的最重要症状是治疗组与对照组相比，体型较小且无生长。SEM 和 TEM 分析的结果表明，与光镜相比，寄生虫的形态和结构细节更好，并且表明研究的物种是伊朗特有的一种本地（）株，其大小和其他特征是独特的，并且是首次在本研究中引入。
