ABSTRACT

In this study, an entomopathogenic fungus was isolated from whitefly (Bemisia tabaci) cadaver samples collected from eggplant fields in Barka, Oman. The fungus was identified as Cordyceps javanica based on sequence analysis of ribosomal DNA internal transcribed spacer (ITS) regions. Under in vitro conditions, the fungus was able to grow between 20°C and 30°C, with a maximum growth at 30°C. No growth occurred at 35°C. Studies on the efficacy of different concentrations of conidia of C. javanica against whitefly nymphs revealed that the mortality rate increased with the increase in concentrations of inoculum. About 95.6 ± 2.1% corrected mortality was recorded at a concentration of 10⁷ conidia ml⁻¹ after 7 days of treatment. The culture filtrate of C. javanica exhibited toxicity against whitefly nymphs and recorded 61.3 ± 9.5% corrected mortality after 48 h of treatment. There was no significant difference between the mortality caused by conidial suspension and culture filtrate. Gas chromatography-mass spectrometry (GC-MS) analysis revealed the presence of 17 compounds in the culture filtrate of C. javanica. Lauric acid was present in the largest amount (28.7%) and the long chain (C22-25) hydrocarbons contributed 38.3%. This is the first report on the isolation and characterization of C. javanica from B. tabaci from Oman.

摘要

在这项研究中，从阿曼巴卡茄田采集的粉虱（Bemisia tabaci）尸体样品中分离出一种致病真菌。根据核糖体DNA内部转录间隔区（ITS）区域的序列分析，将真菌鉴定为冬虫夏草。在体外条件下，真菌能够在20°C至30°C之间生长，在30°C时最大生长。在35℃下没有生长发生。对不同浓度的爪哇分生孢子分生孢子对粉虱若虫的功效的研究表明，死亡率随着接种物浓度的增加而增加。在10 ⁷分生孢子ml ^-1的浓度下，记录的校正死亡率约为95.6±2.1％治疗7天后。处理48小时后，爪哇念珠菌的培养物滤液对粉虱若虫表现出毒性，记录的校正死亡率为61.3±9.5％。分生孢子悬浮液和培养物滤液引起的死亡率之间没有显着差异。气相色谱-质谱（GC-MS）分析显示爪哇梭菌的培养滤液中存在17种化合物。月桂酸含量最高（28.7％），长链（C22-25）碳氢化合物占38.3％。这是对的分离和鉴定的第一份报告C.鸦胆子从烟粉虱从阿曼。